Acetic acid: chemical formula, properties and applications. Melting point of acetic acid

Acetic acid (methanecarboxylic acid, ethanoic acid) CH3COOH- colorless liquid with a pungent odor and sour taste. Anhydrous acetic acid is called"icy". Melting point is 16.75° C, boiling point 118.1°; 17.1° at 10 mm pressure. rt. column, 42.4 ° at 40 mm., 62.2 ° at 100 mm., 98.1 ° at 400 mm. and 109° at 560 mm. mercury column.

The specific heat capacity of acetic acid is 0.480 cal/g. deg., combustion Q 209, 4 kcal/mol.

Acetic acid belongs to weak acids, dissociation constant K = 1, 75 . 10 -5 . It is miscible in all respects with water, alcohol, ether, benzene and is insoluble in carbon disulfide. When acetic acid is diluted with water, the volume of the solution decreases. Maximum Density 1, 0748 g/cm 3 corresponds to monohydrate.

Acetic acid is the first acid that became known to mankind (in the form of vinegar formed when wine sours). It was obtained in concentrated form by Stahl in 1700 year, and the composition was established by Berzelius in 1814 year. Acetic acid is common in plants both in free form and in the form of salts and esters; it is formed during the rotting and fermentation of dairy products. Converting alcoholic liquids into vinegar ( 3-15% acetic acid) occurs under the influence of bacteria« vinegar fungus» Micoderma aceti . From the fermented liquid, distillation is obtained 80% acetic acid - vinegar essence. Acetic acid is produced on a limited scale from« wood vinegar» - one of the products of dry distillation of wood.

The main industrial method for producing acetic acid is the oxidation of acetaldehyde, synthesizedfrom acetylene by Kucherov reaction. Oxidation is carried out with air or oxygen at 60° and catalysis (CH 3 SOS) 2 M n. In this way they get 95-97% acetic acid. In the presence of acetates cobalt and copper at 40° obtain a mixture of acetic acid ( 50-55%), acetic anhydride ( 30-35%) and water (~10%). The mixture is separated by distillation. The oxidation of ethylene, ethyl alcohol and others is also of technical importance for the production of acetic acid, as well as the action sulfuric acid to nitroethane.

Pure acetic acid is obtained from technical products by rectification.

The hydroxyl group of acetic acid is very reactive and can be exchanged for halogens, SH, OC 2 H 5, NH 2, NHNH 2, N 3, NHOH and others with the formation of its various derivatives, for example, acetyl chloride CH 3 SOS l , acetic anhydride(CH 3 CO) 2 O, acetamide CH 3 CO N H 2, azide CH 3 CO N 3 ; Acetic acid is esterified with alcohols, forming esters (acetates) CH 3 COO R , the simplest of which are highly volatile liquids with a fruity odor (for example, amyl acetate and isoamyl acetate« pear essence»), less often with a floral scent (tert-Butylcyclohexyl acetate).

The physical properties of some acetic acid esters are given in the table; they are widely used as solvents (especially ethyl acetate) for nitrocellulose varnishes, glyphthalic and polyester resins, in the production of film and celluloid , as well as in the food industry and perfumery. In the production of polymers, artificial fibers, varnishes and vinyl acetate-based adhesives play a significant role.

Acetic acid has wide and varied uses. In technology, one of its most common reactions is the introduction of an acetyl group CH 3 CO, which is used to protect, for example, in aromatic amines NH 2 - group from oxidation during nitration; receive a number of medicinal substances ( aspirin , phenacetin and others).

Significant quantities of acetic acid are used in the production of acetone, cellulose acetate, synthetic dyes, and are used in dyeing and printing fabrics and in the food industry. Basic salts of acetic acid Al, Fe, Cr and others serve as mordants for dyeing; they provide a strong bond of the dye to the textile fiber.

Acetic acid vapors irritate the mucous membranes of the upper respiratory tract. Chronic exposure to vapor leads to diseases of the nasopharynx and conjunctivitis. Maximum permissible concentration of its vapors in the air 0.005 mg/l. Solutions with concentration above 30% cause burns.

Undoubtedly, the most universal of the known solvents related to aliphatic monobasic acids is the well-known acetic acid. It also has other names: vinegar essence or ethanoic acid. The cheapness and availability in different concentrations (from 3 to 100%) of this substance, its stability and ease of purification, have led to the fact that today it is the best and most famous product with the properties of dissolving most substances of organic origin, which is in great demand in various fields human activity.

Acetic acid was the only one that the ancient Greeks knew. Hence its name: “oxos” - sour, sour taste. Acetic acid is the simplest type of organic acids that are an integral part of vegetable and animal fats. It is present in small concentrations in foods and drinks and is involved in metabolic processes during fruit ripening. Acetic acid is often found in plants and animal secretions. Salts and esters of acetic acid are called acetates.

Acetic acid is weak (dissociates only partially in an aqueous solution). However, since an acidic environment inhibits the activity of microorganisms, acetic acid is used in food preservation, for example, in marinades.

Acetic acid is obtained by oxidation of acetaldehyde and other methods, food acetic acid is obtained by acetic acid fermentation of ethanol. It is used to obtain medicinal and aromatic substances, as a solvent (for example, in the production of cellulose acetate), in the form of table vinegar in the manufacture of seasonings, marinades, and canned food. Acetic acid is involved in many metabolic processes in living organisms. It is one of the volatile acids present in almost all foods, sour in taste and the main component of vinegar.

The purpose of this work: to study the properties, production and use of acetic acid.

Objectives of this study:

1. Tell about the history of the discovery of acetic acid

2. Study the properties of acetic acid

3. Describe methods for producing acetic acid

4. Reveal the features of using acetic acid

1. Discovery of acetic acid

The structure of acetic acid has interested chemists since Dumas's discovery of trichloroacetic acid, since this discovery dealt a blow to the then dominant electrochemical theory of Berzelius. The latter, dividing elements into electropositive and electronegative, did not recognize the possibility of substituting in organic substances, without a profound change in their chemical properties, hydrogen (an electropositive element) with chlorine (an electronegative element), and yet, according to the observations of Dumas ("Comptes rendus" of the Paris Academy, 1839 ) it turned out that “the introduction of chlorine in place of hydrogen does not completely change the external properties of the molecule...”, which is why Dumas asks the question “whether electrochemical views and ideas about the polarity attributed to molecules (atoms) of simple bodies are based on such clear facts that they could be considered objects of unconditional faith, but if they must be considered as hypotheses, then do these hypotheses fit the facts?... It must be admitted, he continues, that the situation is different. In inorganic chemistry, our guiding thread is isomorphism, a theory based based on facts, as is well known, there is little agreement with electrochemical theories. In organic chemistry, the theory of substitution plays the same role... and perhaps the future will show that both views are more closely related to each other, that they stem from the same reasons and can be summarized under the same name. In the meantime, based on the transformation of hydrochloric acid into chloroacetic acid and aldehyde into chloraldehyde (chloral) and from the fact that in these cases all hydrogen can be replaced by an equal volume of chlorine without changing the basic chemical character of the substance, we can draw the conclusion that in organic chemistry There are types that are preserved even when we introduce equal volumes of chlorine, bromine and iodine in place of hydrogen. And this means that the theory of substitution rests on facts, and the most brilliant ones at that, in organic chemistry." Citing this excerpt in his annual report of the Swedish Academy ("Jahresbericht etc.", vol. 19, 1840, p. 370). Berzelius notes: “Dumas prepared a compound to which he gives the rational formula C4Cl6O3 + H2O (Atomic weights are modern; trichloroacetic acid is considered as a compound of anhydride with water.); he classifies this observation as one of the faits les plus eclatants de la Chimie organique; this is the basis of his theory of substitution. which, in his opinion, will overturn electrochemical theories..., and yet it turns out that one only has to write his formula a little differently in order to have an oxalic acid compound. with the corresponding chloride, C2Cl6 + C2O4H2, which remains combined with oxalic acid both in acid and in salts. We are, therefore, dealing with this kind of connection, of which many examples are known; many... both simple and complex radicals have the property that their oxygen-containing part can combine with bases and be deprived of them without losing contact with the chlorine-containing part. This view was not presented by Dumas and was not subjected to experimental verification by him, and yet, if it is true, then the new teaching, which, according to Dumas, is incompatible with the hitherto dominant theoretical ideas, has had the ground torn out from under its feet and must fall." Having listed then some inorganic compounds, similar, in his opinion, to chloroacetic acid (Among them, Berzelius also listed the chlorine anhydride of chromic acid - CrO2Cl2, which he considered to be a compound of perchloric chromium (unknown to this day) with chromic anhydride: 3CrO2Cl2 = CrCl6 + 2CrO3) , Berzelius continues: “Dumas' chloroacetic acid obviously belongs to this class of compounds; in it the carbon radical is combined with both oxygen and chlorine. It can, therefore, be oxalic acid, in which half of the oxygen is replaced by chlorine, or a compound of 1 atom (molecule) of oxalic acid with 1 atom (molecule) of carbon sesquichloride - C2Cl6. The first assumption cannot be accepted, because it allows for the possibility of substituting chlorine for 11/2, oxygen atoms (According to Berzelius, oxalic acid was C2O3.). Dumas adheres to a third idea, completely incompatible with the two above, according to which chlorine replaces not oxygen, but electropositive hydrogen, forming the hydrocarbon C4Cl6, which has the same properties of a complex radical as C4H6 or acetyl, and is capable of allegedly producing acid with 3 oxygen atoms, identical in properties with U., but, as can be seen from a comparison (of their physical properties), completely different from it." How deeply Berzelius at that time was deeply convinced of the different constitution of acetic and trichloroacetic acid can be clearly seen from the remark he made about same year (“Jahresb.”, 19, 1840, 558) regarding Gerard’s article (“Journ. f. pr. Ch.”, XIV, 17): “Gerard, he says, expressed a new view on the composition of alcohol, ether and their derivatives; it is as follows: the known compound of chromium, oxygen and chlorine has the formula = CrO2Cl2, chlorine replaces the oxygen atom in it (Berzelius implies 1 oxygen atom of chromic anhydride - CrO3). U. acid C4H6 + 3O contains 2 atoms (molecules) of oxalic acid, of which in one all the oxygen is replaced by hydrogen = C2O3 + C2H6. And 37 pages are filled with this game of formulas. But already the next year, Dumas, further developing the idea of ​​types, pointed out that, speaking about the identity of the properties of U. and trichloroacetic acid, he meant the identity of their chemical properties, clearly expressed, for example, in the analogy of their decomposition under the influence of alkalis: C2H3O2K + KOH = CH4 + K2CO8 and C2Cl3O2K + KOH = CHCl3 + K2CO8, since CH4 and CHCl3 are representatives of the same mechanical type. On the other hand, Liebig and Graham publicly spoke out for greater simplicity, achieved on the basis of the theory of substitution, when considering the chloro derivatives of ordinary ether and esters of formic acid and uranium, obtained by Malagutti, and Berzelius, yielding to the pressure of new facts, in the 5th ed. of his “Lehrbuch der Chemie” (Preface marked November 1842), having forgotten his harsh review of Gerard, found it possible to write the following: “If we recall the transformation (decomposition in the text) of acetic acid under the influence of chlorine into chloroxalic acid (Chloroxalsaure - Berzelius calls trichloroacetic acid ("Lehrbuch", 5th ed., p. 629), then it seems possible yet another view on the composition of acetic acid (acetic acid is called Acetylsaure by Berzelius), namely, it can be a combined oxalic acid, in which the combining group (Paarling) is C2H6, just as the combining group in chloro-oxalic acid is C2Cl6, and then the action of chlorine on acetic acid would consist only of converting C2H6 into C2Cl6 It is, of course, impossible to decide whether this view is more correct. .., however, it is useful to pay attention to the possibility of it."

Thus, Berzelius had to admit the possibility of replacing hydrogen with chlorine without changing the chemical function of the original body in which the replacement took place. Without dwelling on the application of his views to other compounds, I turn to the works of Kolbe, who for acetic acid, and then for other limiting monobasic acids, found a number of facts that were in harmony with the views of Berzelius (Gerard). The starting point for Kolbe’s work was the study of a crystalline substance, the composition CCl4SO2, previously obtained by Berzelius and Marsay by the action of aqua regia on CS2 and formed by Kolbe by the action of wet chlorine on CS2. Through a series of transformations, Kolbe (See Kolbe, “Beitrage znr Kenntniss der gepaarten Verbindungen” (“Ann. Ch. u. Ph.”, 54, 1845, 145).) showed that this body is, in modern terms, the chlorine anhydride of trichloromethylsulfonic acid, CCl4SO2 = CCl3.SO2Cl (Kolbe called it Schwefligsaures Kohlensuperchlorid), capable, under the influence of alkalis, of giving salts of the corresponding acid - CCl3.SO2(OH) [according to Kolbe HO + C2Cl3S2O5 - Chlorkohlenunterschwefelsaure] (Atomic weights: H = 2, Cl = 71 , C=12 and O=16; and therefore with modern atomic weights it is C4Cl6S2O6H2.), which, under the influence of zinc, first replaces one Cl atom with hydrogen, forming the acid CHCl2.SO2(OH) [according to Kolbe - wasserhaltige Chlorformylunterschwefelsaure (Berzelius (“ Jahresb. "25, 1846, 91) notes that it is correct to consider it a combination of dithionic acid S2O5 with chloroformyl, which is why he calls CCl3SO2(OH) Kohlensuperchlorur (C2Cl6) - Dithionsaure (S2O5). Hydration water, as usual, is not taken into account by Berzelius .), and then another, forming the acid CH2Cl.SO2(OH) [according to Kolbe - Chlorelaylunterschwefelsaure], and finally, when reduced by current or potassium amalgam (The reaction was recently used by Melsans to reduce trichloroacetic acid to acetic acid.) replaces hydrogen and all three Cl atoms, forming methylsulfonic acid. CH3.SO2(OH) [according to Kolbe - Methylunterschwefelsaure]. The analogy of these compounds with chloroacetic acids was involuntarily striking; Indeed, with the formulas of that time, two parallel series were obtained, as can be seen from the following table: H2O+C2Cl6.S2O5 H2O+C2Cl6.C2O3 H2O+C2H2Cl4.S2O5 H2O+C2H2Cl4.C2O3 H2O+C2H4Cl2.S2O5 H2O+C2H4Cl2.C2O3 H2O+C2H6. S2O5 H2O+C2H6.C2O3 This did not escape Kolbe, who notes (I. p. 181): “to the combined sulfurous acids described above and directly in chlorocarbon-sulfurous acid (above - H2O+C2Cl6. S2O5) is adjacent to chloro-oxalic acid, also known as chloroacetic acid. Liquid chlorocarbon - CCl (Cl = 71, C = 12; now we write C2Cl4 - this is chloroethylene.), as is known, transforms in light under the influence of chlorine into hexachloroethane (according to the then nomenclature - Kohlensuperchlorur), and one can expect that if If it were simultaneously exposed to water, then it, like bismuth chloride, antimony chloride, etc., at the moment of formation, will replace chlorine with oxygen. Experience confirmed the assumption." Under the action of light and chlorine on C2Cl4, which was under water, Kolbe obtained, along with hexachloroethane, trichloroacetic acid and expressed the transformation with the following equation: (Since C2Cl4 can be obtained from CCl4 by passing it through a heated) tube, and CCl4 is formed by the action, upon heating, of Cl2 on CS2; then Kolbe’s reaction was the first in time to synthesize acetic acid from elements.) “Whether free oxalic acid is also formed at the same time is difficult to decide, since in the light chlorine immediately oxidizes it into acetic acid "... Berzelius's view of chloroacetic acid "is surprisingly (auf eine tiberraschende Weise) confirmed by the existence and parallelism of the properties of combined sulfurous acids, and, as it seems to me (says Kolbe I. p. 186), goes beyond the realm of hypotheses and acquires high degree of probability. For if chlorocarbonaceous acid (Chlorkohlenoxalsaure is how Kolbe now calls chloroacetic acid.) has a composition similar to that of chlorocarbonaceous acid, then we must also consider acetic acid, which is responsible for methyl sulfurous acid, as a combined acid and consider it as methyl oxalic acid: C2H6.C2O3 (This is a view previously expressed by Gerard). It is not incredible that in the future we will be forced to accept as combined acids a significant number of those organic acids in which at present, due to the limited knowledge of our information, we accept hypothetical radicals...” “As for the phenomena of substitution in these combined acids, then they receive a simple explanation from the fact that various, probably isomorphic compounds are capable of replacing each other in the role of combining groups (als Raarlinge, l. p. 187), without significantly changing the acidic properties of the body combined with them! "Further experimental confirmation We find this view in the article of Frankland and Kolbe: "Ueber die chemische Constitution der Sauren der Reihe (CH2)2nO4 und der unter den Namen "Nitrile" bekannten Verbindungen" ("Ann. Chem. n. Pharm. ", 65, 1848, 288). Based on the idea that all acids of the series (CH2)2nO4 are structured similarly to methyl oxalic acid (Now we write CnH2nO2 and call methyl oxalic acid acetic acid.), they note the following: “if the formula is H2O + H2 .C2O3 represents the true expression of the rational composition of formic acid, that is, if it is considered as oxalic acid combined with one equivalent of hydrogen (The expression is not correct; instead of H, Frankland and Kolbe use a crossed out letter, which is equivalent to 2 H), then The transformation of ammonium formic acid into aqueous hydrocyanic acid at high temperatures is easily explained, because it is known, and was found by Dobereiner, that ammonium oxalate decomposes when heated into water and cyanogen. The hydrogen combined in formic acid participates in the reaction only in that it combines with cyanogen to form hydrocyanic acid: The reverse formation of formic acid from hydrocyanic acid under the influence of alkalis is nothing more than a repetition of the well-known transformation of cyanogen dissolved in water into oxalic acid and ammonia, with this only difference; that at the moment of formation, oxalic acid combines with the hydrogen of hydrocyanic acid." The fact that benzene cyanide (C6H5CN), for example, according to Fehling, does not have acidic properties and does not form Prussian blue can, according to Kolbe and Frankland, be put in parallel with the inability chlorine of ethyl chloride to the reaction with AgNO3, and the correctness of their induction is proved by Kolbe and Frankland by synthesis using the nitriles method (Nitriles were obtained by distillation of sulfuric acids with KCN (method of Dumas and Malagutti with Leblanc): R".SO3(OH)+KCN=R. CN + KHSO4) acetic, propionic (according to the then, meth-acetonic) and caproic acids. Then, the next year, Kolbe subjected to electrolysis alkaline salts of monobasic saturated acids and, in accordance with his scheme, observed at the same time, during the electrolysis of acetic acid, the formation of ethane, carbonic acid and hydrogen: H2O+C2H6.C2O3=H2+, and during the electrolysis of valeric acid - octane, carbonic acid and hydrogen: H2O+C8H18.C2O3=H2+. However, it is impossible not to notice that Kolbe expected to obtain from acetic acid methyl (CH3)" combined with hydrogen, i.e., swamp gas, and from valerian acid - butyl C4H9, also combined with hydrogen, i.e. C4H10 (he calls C4H9 valyl), but in this expectation one must see a concession to the formulas of Gerard, who had already received significant rights of citizenship, who abandoned his previous view of acetic acid and considered it not to be C4H8O4, which formula, judging by cryoscopic data, it actually has, and for C2H4O2, as it is written in all modern chemistry textbooks.

Through Kolbe's work, the structure of acetic acid, and at the same time all other organic acids, was finally clarified and the role of subsequent chemists was reduced only to division - due to theoretical considerations and the authority of Gerard, Kolbe's formulas in half and to translating them into the language of structural views, due to which the formula C2H6.C2O4H2 turned into CH3.CO(OH).

2. Properties of acetic acid

Carboxylic acids are organic compounds containing one or more carboxyl groups –COOH linked to a hydrocarbon radical.

The acidic properties of carboxylic acids are due to a shift in electron density to carbonyl oxygen and the resulting additional (compared to alcohols) polarization of the O–H bond.
In an aqueous solution, carboxylic acids dissociate into ions:

With increasing molecular weight, the solubility of acids in water decreases.
According to the number of carboxylic groups, acids are divided into monobasic (monocarboxylic) and polybasic (dicarboxylic, tricarboxylic, etc.).

Based on the nature of the hydrocarbon radical, saturated, unsaturated and aromatic acids are distinguished.

Systematic names of acids are given by the name of the corresponding hydrocarbon with the addition of a suffix -new and words acid. Trivial names are also often used.

Some saturated monobasic acids

Carboxylic acids exhibit high reactivity. They react with various substances and form a variety of compounds, among which are of great importance functional derivatives, i.e. compounds obtained as a result of reactions at the carboxyl group.

2.1 Formation of salts
a) when interacting with metals:

2RCOOH + Mg ® (RCOO) 2 Mg + H 2

b) in reactions with metal hydroxides:

2RCOOH + NaOH ® RCOONa + H 2 O

Instead of carboxylic acids, their acid halides are more often used:
Amides are also formed by the interaction of carboxylic acids (their acid halides or anhydrides) with organic ammonia derivatives (amines):

Amides play an important role in nature. Molecules of natural peptides and proteins are built from a-amino acids with the participation of amide groups - peptide bonds.

Acetic (ethanoic acid).

Formula: CH 3 – COOH; clear, colorless liquid with a pungent odor; below the melting point (mp 16.6 degrees C) is an ice-like mass (therefore concentrated acetic acid is also called glacial acetic acid). Soluble in water, ethanol.

Table 1. Physical properties of acetic acid

Synthetic food grade acetic acid is a colorless, transparent, flammable liquid with a pungent odor of vinegar. Synthetic food grade acetic acid is produced from methanol and carbon monoxide over a rhodium catalyst. Synthetic food acetic acid is used in the chemical, pharmaceutical and light industries, as well as in the food industry as a preservative. Formula CH 3 COOH.

Synthetic food acetic acid is available concentrated (99.7%) and in the form of an aqueous solution (80%).

In terms of physicochemical parameters, synthetic food acetic acid must meet the following standards:

Table 2. Basic technical requirements

Indicator name	Norm
1. Appearance	Colorless, transparent liquid without mechanical impurities
2. Solubility in water	Complete, transparent solution
3. Mass fraction of acetic acid, %, not less	99,5
4. Mass fraction of acetaldehyde, %, no more	0,004
5. Mass fraction of formic acid, %, no more	0,05
6. Mass fraction of sulfates (SO 4),%, no more	0,0003
7. Mass fraction of chlorides (Cl),%, no more	0,0004
8. Mass fraction of heavy metals precipitated by hydrogen sulfide (Pb), %, no more	0,0004
9. Mass fraction of iron (Fe), %, no more	0,0004
10. Mass fraction of non-volatile residue, %, no more	0,004
11. Color fastness of potassium permanganate solution, min, not less	60
12. Mass fraction of substances oxidized by potassium dichromate, cm 3 sodium thiosulfate solution, concentration c (Na 2 SO 3 * 5H 2 O) = 0.1 mol/dm 3 (0.1H), no more	5,0

Synthetic food acetic acid is a flammable liquid, and according to the degree of impact on the body, it belongs to substances of the 3rd hazard class. When working with acetic acid, personal protective equipment (filter gas masks) should be used. First aid for burns is rinsing with plenty of water.

Synthetic food acetic acid is poured into clean railway tanks, tank trucks with an internal surface made of stainless steel, into stainless steel containers, tanks and barrels with a capacity of up to 275 dm3, as well as into glass bottles and polyethylene barrels with a capacity of up to 50 dm3. Polymer containers are suitable for filling and storing acetic acid for one month. Synthetic food grade acetic acid is stored in sealed stainless steel containers. Containers, containers, barrels, bottles and polyethylene flasks are stored in warehouses or under a canopy. Shared storage with strong oxidizing agents (nitric acid, sulfuric acid, potassium permanganate, etc.) is not allowed.

Transported in railway tanks made of stainless steel grade 12Х18H10Т or 10Х17H13М2Т, with top discharge.

3. Preparation of acetic acid

Acetic acid is an important chemical product that is widely used in industry to produce esters, monomers (vinyl acetate), in the food industry, etc. Its global production reaches 5 million tons per year. Until recently, the production of acetic acid was based on petrochemical raw materials. In the Walker process, ethylene is oxidized under mild conditions with atmospheric oxygen to acetaldehyde in the presence of a catalytic system of PdCl2 and CuCl2. Next, acetaldehyde is oxidized to acetic acid:

CH2=CH2 + 1/2 O2 CH3CHO CH3COOH

According to another method, acetic acid is obtained by the oxidation of n-butane at a temperature of 200 C and a pressure of 50 atm in the presence of a cobalt catalyst.

The elegant Walker process - one of the symbols of the development of petrochemicals - is gradually being replaced by new methods based on the use of coal raw materials. Methods have been developed for producing acetic acid from methanol:

CH3OH + CO CH3COOH

This reaction, which is of great industrial importance, is an excellent example illustrating the success of homogeneous catalysis. Since both CH3OH and CO can be produced from coal, the carbonylation process should become more economical as oil prices rise. There are two industrial processes for the carbonylation of methanol. In the older method, developed at BASF, a cobalt catalyst was used, the reaction conditions were harsh: temperature 250? C and pressure 500-700 atm. In another process, mastered by Monsanto, a rhodium catalyst was used, the reaction was carried out at lower temperatures (150-200 C) and pressure (1-40 atm). The history of the discovery of this process is interesting. The company's scientists investigated hydroformylation using rhodium phosphine catalysts. The technical director of the petrochemical department proposed using the same catalyst for the carbonylation of methanol. The results of the experiments turned out to be negative, and this was associated with the difficulty of forming a metal-carbon bond. However, remembering a lecture from a company consultant about the easy oxidative addition of methyl iodide to metal complexes, the researchers decided to add an iodine promoter to the reaction mixture and obtained a brilliant result, which they did not believe at first. A similar discovery was also made by scientists from a competing company, Union Carbide, who were only a few months behind. The team developing the methanol carbonylation technology, after just 5 months of intensive work, created the industrial Monsanto process, with the help of which 150 thousand tons of acetic acid were produced in 1970. This process became the harbinger of the field of science that was called C1-chemistry.

The mechanism of carbonylation has been thoroughly investigated. Methyl iodide required for the reaction is obtained from the equation

CH3OH + HI CH3I + H2O

The catalytic cycle can be represented as follows:

Methyl iodide oxidatively attaches to the square-planar complex (I) to form six-coordinate complex II, then, as a result of the introduction of CO at the methyl-rhodium bond, acetylrhodium complex (III) is formed. Reductive elimination of acetic acid iodide regenerates the catalyst, and hydrolysis of acetic acid iodide produces acetic acid.

Industrial synthesis of acetic acid:

a) catalytic oxidation of butane

2CH3–CH2–CH2–CH3 + 5O2 t 4CH3COOH + 2H2O

b) heating a mixture of carbon monoxide (II) and methanol on a catalyst under pressure

CH3OH + CO CH3COOH

Production of acetic acid by fermentation (acetic acid fermentation).

Raw materials: ethanol-containing liquids (wine, fermented juices), oxygen.

Excipients: enzymes of acetic acid bacteria.

Chemical reaction: ethanol is biocatalytically oxidized to acetic acid.

CH 2 – CH – OH + O 2 CH 2 – COOH + H 2 O

Main product: acetic acid.

4. Application of acetic acid

Acetic acid is used to obtain medicinal and aromatic substances, as a solvent (for example, in the production of cellulose acetate), in the form of table vinegar in the manufacture of seasonings, marinades, and canned food.

An aqueous solution of acetic acid is used as a flavoring and preservative (seasoning food, pickling mushrooms, vegetables).

Vinegar contains acids such as malic, lactic, ascorbic, and acetic.

Apple cider vinegar (4% acetic acid)

Apple cider vinegar contains 20 essential minerals and trace elements, as well as acetic, propionic, lactic and citric acids, a number of enzymes and amino acids, and valuable ballast substances such as potash and pectin. Apple cider vinegar is widely used in preparing various dishes and canning. It goes well with all kinds of salads, both fresh vegetables and meat and fish. You can marinate meat, cucumbers, cabbage, capers, purslane, and truffles in it. However, in the West, apple cider vinegar is known more for its medicinal properties. It is used for high blood pressure, migraines, asthma, headaches, alcoholism, dizziness, arthritis, kidney disease, high fever, burns, bedsores, etc.

Healthy people are recommended to drink a healthy and refreshing drink every day: stir a spoonful of honey in a glass of water and add 1 spoonful of apple cider vinegar. For those who want to lose weight, we recommend drinking a glass of unsweetened water with two tablespoons of apple cider vinegar every time you eat.

Vinegar is widely used in home canning to prepare marinades of various strengths. In folk medicine, vinegar is used as a nonspecific antipyretic (by rubbing the skin with a solution of water and vinegar in a 3:1 ratio), as well as for headaches using the lotion method. It is common to use vinegar for insect bites through compresses.

The use of alcohol vinegar in cosmetology is known. Namely, to give softness and shine to hair after perm and permanent coloring. To do this, it is recommended to rinse your hair with warm water with the addition of alcohol vinegar (3-4 tablespoons of vinegar per 1 liter of water).

Grape vinegar (4% acetic acid)

Grape vinegar is widely used by leading chefs not only in Slovenia, but throughout the world. In Slovenia, it is traditionally used in the preparation of various vegetable and seasonal salads (2-3 tablespoons per salad bowl), because it gives a unique and refined taste to the dish. Also, grape vinegar goes well with various fish salads and seafood dishes. When preparing kebabs from various types of meat, but especially pork, grape vinegar is simply irreplaceable.

Acetic acid is also used for the production of medicines.

Aspirin tablets (AS) contain the active ingredient acetylsalicylic acid, which is the acetic ester of salicylic acid.

Acetylsalicylic acid is produced by heating salicylic acid with anhydrous acetic acid in the presence of a small amount of sulfuric acid (as a catalyst).

When heated with sodium hydroxide (NaOH) in aqueous solution, acetylsalicylic acid hydrolyzes to sodium salicylate and sodium acetate. When the medium is acidified, salicylic acid precipitates and can be identified by its melting point (156-1600C). Another method of identifying salicylic acid formed during hydrolysis is to color its solution dark purple when ferric chloride (FeCl3) is added. The acetic acid present in the filtrate is converted by heating with ethanol and sulfuric acid into ethoxyethanol, which can be easily recognized by its characteristic odor. In addition, acetylsalicylic acid can be identified using various chromatographic methods.

Acetylsalicylic acid crystallizes to form colorless monoclinic polyhedra or needles, slightly sour in taste. They are stable in dry air but gradually hydrolyze to salicylic acid and acetic acid in humid environments (Leeson and Mattocks, 1958; Stempel, 1961). The pure substance is a white crystalline powder with almost no odor. The smell of acetic acid indicates that the substance has begun to hydrolyze. Acetylsalicylic acid undergoes esterification under the action of alkaline hydroxides, alkaline bicarbonates, and also in boiling water.

Acetylsalicylic acid has anti-inflammatory, antipyretic, and analgesic effects, and is widely used for feverish conditions, headaches, neuralgia, etc., and as an antirheumatic agent.

Acetic acid is used in the chemical industry (production of cellulose acetate, from which acetate fiber, organic glass, film are produced; for the synthesis of dyes, medicines and esters), in the production of non-flammable films, perfumery products, solvents, in the synthesis of dyes, medicinal substances, for example , aspirin. Salts of acetic acid are used to control plant pests.

Conclusion

So, acetic acid (CH3COOH), a colorless flammable liquid with a pungent odor, is highly soluble in water. It has a characteristic sour taste and conducts electricity. The use of acetic acid in industry is very large.

Acetic acid produced in Russia is at the level of the best world standards, is in high demand on the world market and is exported to many countries around the world.

The production of acetic acid has a number of its own specific requirements, so specialists are needed who have extensive experience not only in the field of production automation and process control, but also clearly understand the special requirements of this industry.

List of used literature

1. Artemenko, Alexander Ivanovich. Chemistry reference guide / A.I. Artemenko, I.V. Tikunova, V.A. Painted. - 2nd ed., revised. and additional - M.: Higher School, 2002. - 367 p.

2. Akhmetov, Nail Sibgatovich. General and inorganic chemistry: Textbook for students. chemical technology specialist. universities / Akhmetov N.S. - 4th ed. / revised - M.: Higher School, 2002. - 743 p.

3. Berezin, Boris Dmitrievich. Course of modern organic chemistry: Proc. aid for students universities, educational in chemical technology special/ Berezin B.D., Berezin D.B.-M.: Higher school, 2001.-768 p.

4. I. G. Bolesov, G. S. Zaitseva. Carboxylic acids and their derivatives (synthesis, reactivity, application in organic synthesis). Teaching materials for the general course of organic chemistry. Issue 5. Moscow 1997

5. Sommer K. Accumulator of knowledge in chemistry. Per. with German, 2nd ed. – M.: Mir, 1985. – 294 p.

6. Karakhanov E.A. Synthesis gas as an alternative to oil. I. Fischer-Tropsch process and oxo-synthesis // Soros Educational Journal. 1997. No. 3. P. 69-74.

7. Karavaev M.M., Leonov E.V., Popov I.G., Shepelev E.T. Synthetic methanol technology. M., 1984. 239 p.

8. Catalysis in C1-chemistry / Ed. V. Kaima. M., 1983. 296 p.

9. Reutov, Oleg Alexandrovich. Organic chemistry: Textbook for students. universities, educational for example and special "Chemistry"/Reutov O.A., Kurts A.L. Butin K.P.-M.: Moscow State University Publishing House.-21 cm. Part 1.-1999.-560 p.

10. Soviet encyclopedic dictionary, ch. ed. A.M. Prokhorov - Moscow, Soviet Encyclopedia, 1989

11. Chemistry: Reference Guide, Ch. ed. N.R. Lieberman - St. Petersburg, Khimiya Publishing House, 1975

12. Chemistry: Organic chemistry: Educational publication for 10th grade. avg. school - Moscow, Enlightenment, 1993

Sommer K. Accumulator of knowledge in chemistry. Per. with German, 2nd ed. – M.: Mir, 1985. P. 199.

I. G. Bolesov, G. S. Zaitseva. Carboxylic acids and their derivatives (synthesis, reactivity, application in organic synthesis). Teaching materials for the general course of organic chemistry. Issue 5. Moscow 1997, p. 23

Sommer K. Accumulator of knowledge in chemistry. Per. with German, 2nd ed. – M.: Mir, 1985. P. 201

Karakhanov E.A. Synthesis gas as an alternative to oil. I. Fischer-Tropsch process and oxo-synthesis // Soros Educational Journal. 1997. No. 3. P. 69

Sommer K. Accumulator of knowledge in chemistry. Per. with German, 2nd ed. – M.: Mir, 1985. P. 258.

Sommer K. Accumulator of knowledge in chemistry. Per. with German, 2nd ed. – M.: Mir, 1985. P. 264

Acetic acid (Acetic acid, ethanoic acid, E260) is a weak, saturated monobasic carboxylic acid.

Acetic acid is a colorless liquid with a characteristic pungent odor and sour taste. Hygroscopic. Unlimitedly soluble in water. Chemical formula CH3COOH.

A 70-80% aqueous solution of acetic acid is called vinegar essence, and 3-6% is called vinegar. Aqueous solutions of acetic acid are widely used in the food industry and household cooking, as well as in canning.

A product of natural souring of dry grape wines and fermentation of alcohols and carbohydrates. Participates in metabolism in the body. Widely used in the preparation of canned food, marinades, and vinaigrettes.

Acetic acid is used to obtain medicinal and fragrant substances, as a solvent (for example, in the production of cellulose acetate, acetone). It is used in printing and dyeing.

Salts and esters of acetic acid are called acetates.

The food additive E260 is known to everyone as acetic acid or vinegar. Additive E260 is used in the food industry as an acidity regulator. Acetic acid is mainly used in the form of aqueous solutions in proportions of 3-9% (vinegar) and 70-80% (acetic essence). Additive E260 has a characteristic pungent odor. In aqueous solutions, the acidity regulator E260 is a rather weak acid. In its pure form, acetic acid is a colorless, caustic liquid that absorbs moisture from the environment and freezes already at a temperature of 16.5 °C to form solid colorless crystals. Chemical formula of acetic acid: C 2 H 4 O 2.

Vinegar was known several thousand years ago as a natural fermentation product of beer or wine. In 1847, German chemist Hermann Kolbe first synthesized acetic acid in the laboratory. Currently, only 10% of the total production of acetic acid is extracted using natural methods in the world. But the natural fermentation method is still important, as many countries have laws requiring only biologically derived acetic acid to be used in the food industry. In the biochemical production of the E260 additive, the ability of some bacteria to oxidize ethanol (alcohol) is used. This method is known as acetic acid fermentation. Fermented juices, wine, or a solution of alcohol in water are used as raw materials for the production of E260 additive. There are also a number of methods for synthesizing acetic acid in industry. The most popular of these, accounting for more than half of the world's acetic acid synthesis, involves the carbonylation of methanol in the presence of catalysts. The starting components for this reaction are methanol (CH 3 OH) and carbon monoxide (CO).

Acetic acid is essential for the functioning of the human body. Its derivatives help break down carbohydrates and fats in the body that enter the body with food. Acetic acid is released during the activity of certain types of bacteria, in particular Clostridium acetobutylicum and bacteria of the genus Acetobacter. These bacteria are found everywhere in water, soil, food and naturally enter the human body.

The toxic effect of the E260 additive on the human body depends on the degree of dilution of acetic acid with water. Solutions in which the concentration of acetic acid is higher than 30% are considered dangerous to health and life. Highly concentrated acetic acid in contact with skin and mucous membranes can cause severe chemical burns.

In the food industry, the E260 additive is used for baking confectionery, canning vegetables, producing mayonnaise and other food products.

The acidity regulator E260 is approved for use in food products in all countries as an additive safe for human health.

Acetic acid is also used:

• in everyday life (removing scale from teapots, caring for surfaces);
• in the chemical industry (as a solvent and chemical reagent);
• in medicine (obtaining medicines);
• in other industries.

Food preservative E260 Acetic acid is well known to all people who are interested in the art of gastronomy. This product is the result of souring grape wines under natural conditions, under which fermentation of alcohol and carbohydrates occurs. In addition, it is known that acetic acid is directly involved in metabolic processes in the human body.

Acetic acid has a pungent odor, but in its pure form it is a completely colorless liquid that can absorb moisture from the environment. This substance can freeze at a temperature of minus 16 degrees, resulting in the formation of transparent crystals.

It is noteworthy that a 3-6% solution of acetic acid is called vinegar, while a 70-80 percent solution produces vinegar essence. Water-based E260 solutions are widely used not only in the food industry, but also in household cooking. The main use of the food preservative E260 Acetic acid is the production of marinades and canned food.

In addition, this substance is actively added in the industrial production of a number of confectionery products, as well as mayonnaise and canned vegetables. Often, if there is special need, the food preservative E260 Acetic acid can be used as a disinfectant and disinfectant.

However, food production is not the only area where E260 food preservative is used. Thus, it is widely used in chemical production in the production of organic glass, acetate fiber, as well as in the production of ethers and medicines.

By the way, in pharmacology the so-called acetic ester is widely used, which is better known to people under the name acetylsalicylic acid or aspirin. As a solvent, acetic acid also helps people in a number of cases, and salts isolated from its composition are successfully used in the fight against plant pests.

Harmful food preservative E260 Acetic acid

The harm to humans from the food preservative E260 Acetic acid is especially obvious when this substance is consumed in high concentrations, since in this form it is very toxic. By the way, the degree of acid toxicity directly depends on how much it was diluted with water. Solutions whose concentration exceeds 30 percent are considered the most dangerous to health. When mucous membranes or skin come into contact with concentrated acetic acid, severe chemical burns occur.

Food preservative E260 Acetic acid is approved for use in the food industry in all countries of the world, as it is not considered hazardous to health. The only thing that experts recommend in order to avoid possible harm from the food preservative E260 Acetic acid is to limit the consumption of products containing this substance for people with liver and gastrointestinal diseases. Such products are not recommended for children under 6-7 years of age.

An ordinary bottle of food vinegar, which can be found in any housewife's kitchen, contains many other acids and vitamins. Adding a couple of drops of the product to cooked food and salads causes a natural enhancement of taste. But few of us have seriously thought about the properties and real scale of application of the main component - acetic acid.

What is this substance?

The formula of acetic acid is CH 3 COOH, which classifies it as a fatty carboxylic acid. The presence of one carboxyl group (COOH) classifies it as a monobasic acid. The substance is found on the globe in organic form and is obtained synthetically in laboratories. Acid is the simplest, but no less important representative of its series. Easily dissolves in water, hygroscopic.

The physical properties of acetic acid and density change depending on the temperature. At room temperature 20 o C, the acid is in a liquid state and has a density of 1.05 g/cm 3 . It has a specific smell and sour taste. A solution of a substance without impurities hardens and turns into crystals at temperatures below 17 o C. The boiling process of acetic acid begins at temperatures above 117 o C. The methyl group (CH 3) of the acetic acid formula is obtained by the interaction of alcohols with oxygen: fermentation of alcohol substances and carbohydrates, souring of wines

A little history

The discovery of vinegar was one of the first in a series of acids and was accomplished in stages. At first, Arab scientists of the 8th century began to extract acetic acid by distillation. However, even in ancient Rome, this substance, obtained from sour wine, was used as a universal sauce. The name itself is translated from ancient Greek as “sour”. In the 17th century, European scientists managed to obtain a pure substance of the substance. At that time, they derived the formula and discovered an unusual ability - acetic acid in a vapor state ignited with blue fire.

Until the 19th century, scientists found the presence of acetic acid only in organic form - as part of compounds of salts and esters. Contains plants and their fruits: apples, grapes. In the body of humans and animals: sweat, bile. In the early 20th century, Russian scientists accidentally produced acetaldehyde from the reaction of acetylene with mercuric oxide. Today, the consumption of acetic acid is so great that its main production occurs only synthetically on a huge scale.

Extraction methods

Will acetic acid be pure or with impurities in the solution? depends on the extraction method. Edible acetic acid is obtained biochemically during the fermentation of ethanol. In industry, there are several methods for extracting acid. As a rule, reactions are accompanied by high temperature and the presence of catalysts:

• Methanol reacts with carbon (carbonylation).
• Oxidation of the oil fraction with oxygen.
• Pyrolysis of wood.
• oxygen.

The industrial method is more effective and economical than the biochemical method. Thanks to the industrial method, the production of acetic acid in the 20th and 21st centuries has increased hundreds of times compared to the 19th century. Today, the synthesis of acetic acid by carbonylation of methanol provides more than 50% of the total volume produced.

Physical properties of acetic acid and its effect on the indicator

In its liquid state, acetic acid is colorless. The acidity level of pH 2.4 is easily checked with litmus paper. When acetic acid comes into contact with the indicator, it turns it red. The physical properties of acetic acid change visually. When the temperature drops below 16 o C, the substance takes a solid form and resembles small ice crystals. It is easily soluble in water and reacts with a wide range of solvents, except hydrogen sulfide. Acetic acid reduces the total volume of a liquid when diluted with water. Describe for yourself the physical properties of acetic acid, its color and consistency that you observe in the following image.

The substance ignites at a temperature of 455 o C with the release of heat of 876 kJ/mol. The molar mass is 60.05 g/mol. The physical properties of acetic acid as an electrolyte in reactions are weakly manifested. The dielectric constant is 6.15 at room temperature. Pressure, like density, - a variable physical property of acetic acid. At a pressure of 40 mm. rt. Art. and a temperature of 42 o C, the boiling process will begin. But already at a pressure of 100 mm. rt. Art. boiling will occur only at 62 o C.

Chemical properties

When reacting with metals and oxides, the substance exhibits its acidic properties. Perfectly dissolving more complex compounds, the acid forms salts called acetates: magnesium, lead, potassium, etc. The pK value of the acid is 4.75.

When interacting with gases, vinegar enters with subsequent displacement and formation of more complex acids: chloroacetic, iodoacetic. Dissolving in water, the acid dissociates, releasing acetate ions and hydrogen protons. The degree of dissociation is 0.4 percent.

The physical and chemical properties of acetic acid molecules in crystalline form create hydrogen bonded diamers. Also, its properties are necessary in the creation of more complex fatty acids, steroids and the biosynthesis of sterols.

Laboratory tests

Acetic acid can be detected in a solution by identifying its physical properties, such as odor. It is enough to add a stronger acid to the solution, which will begin to displace the vinegar salts, releasing its vapors. By laboratory distillation of CH 3 COONa and H 2 SO 4 it is possible to obtain acetic acid in dry form.

Let's conduct an experiment from the 8th grade chemistry school curriculum. The physical properties of acetic acid are clearly demonstrated by the chemical dissolution reaction. It is enough to add copper oxide to the solution and heat it slightly. The oxide dissolves completely, making the solution bluish in color.

Derivatives

Qualitative reactions of a substance with many solutions form: ethers, amides and salts. However, during the production of other substances, the requirements for the physical properties of acetic acid remain high. It should always have a high degree of dissolution, which means it should not have foreign impurities.

Depending on the concentration of acetic acid in an aqueous solution, a number of its derivatives are isolated. A substance concentration of more than 96% is called glacial acetic acid. Acetic acid 70-80% can be purchased in grocery stores, where it will be called - vinegar essence. Table vinegar has a concentration of 3-9%.

Acetic acid and everyday life

In addition to nutritional properties, acetic acid has a number of physical properties that humanity has found its use in everyday life. A low concentration solution of the substance easily removes plaque from metal products, the surface of mirrors and windows. The ability to absorb moisture is also beneficial. Vinegar is good at eliminating odors in musty rooms and removing stains from vegetables and fruits on clothes.

As it turned out, the physical property of acetic acid - remove fat from the surface - can be used in folk medicine and cosmetology. Hair is treated with a weak solution of food vinegar to give it shine. The substance is widely used to treat colds, remove warts and skin fungi. The use of vinegar in cosmetic wraps to combat cellulite is gaining momentum.

Use in production

In compounds of salts and other complex substances, acetic acid is an indispensable element:

• Pharmaceutical industry. To create: aspirin, antiseptic and antibacterial ointments, phenacetin.
• Production of synthetic fibers. Non-flammable films, cellulose acetate.
• Food industry. For successful preservation, preparation of marinades and sauces, as a food additive E260.
• Textile industry. Included in dyes.
• Production of cosmetics and hygiene products. Aromatic oils, creams to improve skin tone.
• Production of mordants. Used as an insecticide and weed killer.
• Production of varnishes. Technical solvents, acetone production.

The production of acetic acid increases every year. Today its volume in the world is more than 400 thousand tons per month. Acid is transported in durable steel tanks. Storage in plastic containers in many industries due to the high physical and chemical activity of acetic acid is prohibited or limited to several months.

Safety

High concentrations of acetic acid have a third degree of flammability and produce toxic fumes. It is recommended to wear special gas masks and other personal protective equipment when working with acid. Lethal dose for the human body is 20 ml. When a substance gets inside, the acid first burns the mucous membrane and then affects other organs. In such cases, immediate hospitalization is required.

After contact with acid on exposed skin, it is recommended to immediately rinse them with running water. Superficial acid burns can cause tissue necrosis, which also requires hospitalization.

Physiology scientists have found that a person does not necessarily need to take acetic acid - he can do without food additives. But for people with acid intolerance, as well as stomach problems, the substance is contraindicated.

Acetic acid is used in book printing.

The substance has been found in small quantities in honey, bananas and wheat.

By cooling the acetic acid and sharply shaking the container with it, you can observe its sharp solidification.

A small concentration of acetic acid can reduce pain from insect bites, as well as minor burns.

Eating foods low in acetic acid reduces cholesterol levels in the body. The substance stabilizes sugar levels well in diabetics.

Eating protein and carbohydrate foods along with a small amount of acetic acid increases their absorption by the body.

If the food is too salty, just add a couple of drops of vinegar to smooth out the saltiness.

Finally

Thousands of years of use of acetic acid have led to the fact that its physical and chemical properties are used at every step. Hundreds of possible reactions, thousands of useful substances, thanks to which humanity moves on. The main thing is to know all the features of acetic acid, its positive and negative qualities.

We should not forget about the benefits, but we must always remember what harm can be caused by careless handling of high concentration acetic acid. In terms of its danger, it stands next to hydrochloric acid and Always remember safety precautions when using acid. Dilute the essence with water correctly and carefully.

DEFINITION

Acetic (ethanoic) acid is a colorless liquid with a strong irritating odor.

If it gets on mucous membranes, it causes burns. Acetic acid mixes with water in any ratio. Forms azeotropic mixtures with benzene and butyl acetate.

Acetic acid freezes at 16 o C, its crystals resemble ice in appearance, which is why 100% acetic acid is called “glacial”.

Some physical properties of acetic acid are given in the table below:

Preparation of acetic acid

In industry, acetic acid is produced by the catalytic oxidation of n-butane with atmospheric oxygen:

CH 3 -CH 2 -CH 2 -CH 3 + = 2CH 3 -COOH.

Significant quantities of acetic acid are produced by the oxidation of acetaldehyde, which in turn is produced by the oxidation of ethylene with atmospheric oxygen on a palladium catalyst:

CH 2 =CH 2 + = CH 3 -COH + =CH 3 -COOH.

Food acetic acid is obtained from the microbiological oxidation of ethanol (acetic acid fermentation).

When 2-butene is oxidized with potassium permanganate in an acidic environment or with a chromium mixture, the double bond is completely broken to form two molecules of acetic acid:

CH 3 -CH=CH-CH 3 + = 2CH 3 -COOH.

Chemical properties of acetic acid

Acetic acid is a weak monoprotic acid. In an aqueous solution it dissociates into ions:

CH 3 COOH↔H + + CH 3 COOH.

Acetic acid has weak acidic properties, which are associated with the ability of the hydrogen atom of the carboxyl group to be eliminated as a proton.

CH 2 COOH + NaOH = CH 3 COONa + H 2 O.

The interaction of acetic acid with alcohols proceeds through the mechanism of nucleophilic substitution. An alcohol molecule acts as a nucleophile, attacking the carbon atom of the carboxyl group of acetic acid, which carries a partially positive charge. A distinctive feature of this reaction (esterification) is that the substitution occurs at the carbon atom in the state of sp 3 hybridization:

CH 3 -COOH + CH 3 OH = CH 3 O-C(O)-CH 3 + H 2 O.

When reacting with sthionyl chloride, acetic acid is capable of forming acid halides:

CH 3 -COOH + SOCl 2 = CH 3 -C(O)Cl + SO 2 + HCl.

When phosphorus (V) oxide reacts with acetic acid, an anhydride is formed:

2CH 3 -COOH + P 2 O 5 = CH 3 -C(O)-O-C(O)-CH 3 + 2HPO 3.

The reaction of acetic acid with ammonia produces amides. First, ammonium salts are formed, which, when heated, lose water and turn into amides:

CH 3 -COOH + NH 3 ↔CH 3 -COO - NH 4 + ↔CH 3 -C(O)-NH 2 + H 2 O.

Application of acetic acid

Acetic acid has been known since ancient times; its 3 - 6% solutions (table vinegar) are used as a flavoring and preservative. The preservative effect of acetic acid is due to the fact that the acidic environment it creates suppresses the development of putrefactive bacteria and mold fungi.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	How will the pH of a 0.010 M acetic acid solution change if potassium chloride is added to it to a final concentration of 0.020 M?
Solution	Acetic acid is weak, so in the absence of a foreign electrolyte the ionic strength can be taken to be zero. This gives the right to use the thermodynamic acidity constant to calculate pH. a(H +) = √K 0 (CH 3 COOH) × c(CH 3 COOH); a(H+) = √1.75×10 -5 × 1.0×10 -2 = 4.18×10 -4 M; To calculate the pH after adding potassium chloride, it is necessary to calculate the real acidity constant of acetic acid: K(CH 3 COOH) = K 0 (CH 3 COOH) / γ(H +) × γ(CH 3 COO -). We calculate the ionic strength created by potassium and chloride ions: I = ½ × (0.020 × 1 2 + 0.020 × 1 2) = 0.020. At ionic strength 0.020 γ(H +) = γ(CH 3 COO -) = 0.87. That's why K = 1.75×10 -5 / (0.87)2 = 2.31×10 -5. Hence, = √K 0 (CH 3 COOH) × c(CH 3 COOH); = √2.31×10 -5 ×1.0×10 -2 = 4.80×10 -4 M. So, increasing the ionic strength from zero to 0.020 caused the pH of the acetic acid solution to change by only 0.06 pH units.
Answer	pH will change by only 0.06 units

Ethanoic acid is better known as acetic acid. It is an organic compound with the formula CH 3 COOH. Belongs to the class of carboxylic acids, the molecules of which contain functional monovalent carboxyl groups COOH (either one or several). You can provide a lot of information about it, but now it’s worth noting only the most interesting facts.

Formula

You can see what it looks like from the image below. The chemical formula of acetic acid is simple. This is due to many things: the compound itself is monobasic, and it belongs to the carboxyl group, which is characterized by easy abstraction of protons (a stable elementary particle). This compound is a typical representative of carboxylic acids, since it has all their properties.

The bond between oxygen and hydrogen (−COOH) is highly polar. This causes an easy process of dissociation (dissolution, decay) of these compounds and the manifestation of their acidic properties.

As a result, the H + proton and the acetate ion CH3COO − are formed. What are these substances? An acetate ion is a ligand bound to a specific acceptor (an entity that receives something from a donor compound), forming stable acetate complexes with many metal cations. And a proton is, as mentioned above, a particle capable of capturing an electron with the electronic M-, K- or L-shells of an atom.

Qualitative analysis

It is based specifically on the dissociation of acetic acid. Qualitative analysis, also called reaction, is a set of physical and chemical methods that are used to detect compounds, radicals (independent molecules and atoms) and elements (collections of particles) that make up the substance being analyzed.

Using this method, it is possible to detect salts of acetic acid. It doesn't look as complicated as it might seem. A strong acid is added to the solution. sulfur, for example. And if the smell of acetic acid appears, then its salt is present in the solution. How it works? The residues of acetic acid, which are formed from the salt, at that moment bind with hydrogen cations from sulfuric acid. What is the result? The appearance of more molecules of acetic acid. This is how dissociation happens.

Reactions

It should be noted that the compound under discussion is capable of interacting with active metals. These include lithium, sodium, potassium, rubidium, francium, magnesium, cesium. The latter, by the way, is the most active. What happens during such reactions? Hydrogen is released, and the formation of the notorious acetates occurs. This is what the chemical formula of acetic acid looks like when it reacts with magnesium: Mg + 2CH 3 COOH → (CH 3 COO) 2 Mg + H 2.

There are methods for producing dichloroacetic (CHCl 2 COOH) and trichloroacetic (CCl 3 COOH) acids. In them, the hydrogen atoms of the methyl group are replaced by chlorine ones. There are only two ways to get them. One is the hydrolysis of trichlorethylene. And it is less common than the other, based on the ability of acetic acid to be chlorinated by the action of chlorine gas. This method is simpler and more effective.

This is what this process looks like in the form of the chemical formula of acetic acid reacting with chlorine: CH 3 COOH + Cl 2 → CH 2 CLCOOH + HCL. It’s just worth clarifying one point: this is how you get just chloroacetic acid, the two mentioned above are formed with the participation of red phosphorus in small quantities.

Other transformations

It is worth noting that acetic acid (CH3COOH) is capable of entering into all reactions that are characteristic of the notorious carboxylic group. It can be reduced to ethanol, a monohydric alcohol. To do this, it is necessary to treat it with lithium aluminum hydride, an inorganic compound that is a powerful reducing agent often used in organic synthesis. Its formula is Li(AlH 4).

Acetic acid can also be converted into acid chloride, an active acylating agent. This happens under the influence of thionyl chloride. By the way, it is an acid chloride of sulfurous acid. Its formula is H 2 SO 3. It is also worth noting that the sodium salt of acetic acid, when heated with an alkali, is decarboxylated (the carbon dioxide molecule is eliminated), resulting in the formation of methane (CH₄). And it, as you know, is the simplest hydrocarbon, which is lighter than air.

Crystallization

Glacial acetic acid - the compound in question is often called just that. The fact is that when it is cooled to just 15-16 °C, it goes into a crystalline state, as if it were freezing. Visually it really looks a lot like ice. If you have several ingredients, you can conduct an experiment, the result of which will be the conversion of acetic acid into glacial acid. It's simple. You need to prepare a cooling mixture from water and ice, and then lower a previously prepared test tube with acetic acid into it. After a few minutes it crystallizes. In addition to the connection, this requires a beaker, a tripod, a thermometer and a test tube.

Harm of the substance

Acetic acid, the chemical formula and properties of which were listed above, is unsafe. Its vapors have an irritating effect on the mucous membranes of the upper respiratory tract. The threshold for the perception of the odor of this compound in the air is around 0.4 mg/l. But there is also the concept of maximum permissible concentration - a sanitary and hygienic standard approved by law. According to it, up to 0.06 mg/m³ of this substance can be in the air. And if we are talking about work premises, then the limit increases to 5 mg/m3.

The destructive effect of acid on biological tissue directly depends on how much it is diluted with water. The most dangerous solutions are those containing more than 30% of this substance. And if a person accidentally comes into contact with a concentrated compound, he will not be able to avoid chemical burns. This absolutely cannot be allowed, since after this coagulation necrosis begins to develop - the death of biological tissues. The lethal dose is only 20 ml.

Consequences

It is logical that the higher the concentration of acetic acid, the more harm it will cause if it gets on the skin or inside the body. Common symptoms of poisoning include:

• Acidosis. The acid-base balance shifts towards increasing acidity.
• Blood thickening and impaired clotting.
• Hemolysis of red blood cells, their destruction.
• Liver damage.
• Hemoglobinuria. Hemoglobin appears in the urine.
• Toxic burn shock.

Severity

It is customary to distinguish three:

1. Easy. Characterized by minor burns of the esophagus and oral cavity. But there is no blood thickening, and the internal organs continue to function normally.
2. Average. Intoxication, shock and blood thickening are observed. The stomach is affected.
3. Heavy. The upper respiratory tract and the walls of the digestive tract are severely affected, and kidney failure develops. Maximum pain shock. The development of burn disease is possible.

Poisoning from acetic acid vapor is also possible. It is accompanied by a severe runny nose, cough and watery eyes.

Giving help

If a person is poisoned by acetic acid, it is very important to act quickly to minimize the consequences of what happened. Let's look at what needs to be done:

• Rinse your mouth. Do not swallow water.
• Perform tube gastric lavage. You will need 8-10 liters of cold water. Even blood impurities are not a contraindication. Because in the first hours of poisoning, large vessels still remain intact. So there will be no dangerous bleeding. Before washing, you need to give pain relief with analgesics. The probe is lubricated with Vaseline oil.
• Do not induce vomiting! The substance can be neutralized with burnt magnesia or Almagel.
• None of the above? Then the victim is given ice and sunflower oil - he needs to take a few sips.
• It is permissible for the victim to consume a mixture of milk and eggs.

It is important to provide first aid within two hours after the incident. After this period, the mucous membranes swell greatly, and it will be difficult to reduce a person’s pain. And yes, you should never use baking soda. The combination of acid and alkali will produce a reaction that produces carbon dioxide and water. And such a formation inside the stomach can lead to death.

Application

Aqueous solutions of ethanoic acid are widely used in the food industry. These are vinegars. To obtain them, the acid is diluted with water to obtain a 3-15 percent solution. As an additive they are designated E260. Vinegars are included in various sauces, and they are also used for canning food, marinating meat and fish. In everyday life, they are widely used for removing scale and stains from clothes and dishes. Vinegar is an excellent disinfectant. They can treat any surface. Sometimes it is added during washing to soften clothes.

Vinegar is also used in the production of aromatic substances, medicines, solvents, in the production of acetone and cellulose acetate, for example. Yes, and acetic acid is directly involved in dyeing and printing.

In addition, it is used as a reaction medium for the oxidation of a wide variety of organic substances. An example from industry is the oxidation of paraxylene (an aromatic hydrocarbon) by atmospheric oxygen into terephthalic aromatic acid. By the way, since the vapors of this substance have a sharp irritating odor, it can be used as a replacement for ammonia to bring a person out of fainting.

Synthetic acetic acid

This is a flammable liquid that belongs to substances of the third hazard class. It is used in industry. When working with it, personal protective equipment is used. This substance is stored under special conditions and only in certain containers. Typically this is:

• clean railway tanks;
• containers;
• tank trucks, barrels, stainless steel containers (capacity up to 275 dm 3);
• glass bottles;
• polyethylene barrels with a capacity of up to 50 dm 3;
• sealed stainless steel tanks.

If the liquid is stored in a polymer container, then this is for a maximum of a month. It is also strictly prohibited to store this substance together with such strong oxidizing agents as potassium permanganate, sulfuric and nitric acids.

Composition of vinegar

It’s also worth saying a few words about him. The composition of traditional, familiar vinegar includes the following acids:

• Apple. Formula: NOOCCH₂CH(OH)COOH. It is a common food additive (E296) of natural origin. Contained in unripe apples, raspberries, rowan, barberry and grapes. In tobacco and shag it is presented in the form of nicotine salts.
• Dairy. Formula: CH₃CH(OH)COOH. Formed during the breakdown of glucose. Food additive (E270), which is obtained by lactic acid fermentation.
• Ascorbic acid. Formula: C₆H₈O₆. Food additive (E300) used as an antioxidant that prevents product oxidation.

And of course, the ethane compound is also included in vinegar - this is the basis of this product.

How to dilute?

This is a frequently asked question. Everyone has seen 70% acetic acid on sale. It is bought to prepare mixtures for traditional treatment, or for use as a seasoning, marinade, additive to sauce or dressing. But you cannot use such a powerful concentrate. Therefore, the question arises of how to dilute acetic acid to vinegar. First you need to protect yourself - wear gloves. Then clean water should be prepared. For solutions of different concentrations, a certain amount of liquid will be required. Which? Well, look at the table below and dilute acetic acid based on the data.

Vinegar concentration	Initial concentration of vinegar 70%
	1:1.5 (ratio - one part vinegar to the nth part of water)

In principle, nothing complicated. To get a 9% solution, you need to take the amount of water in milliliters according to this formula: multiply 100 grams of vinegar by the initial value (70%) and divide by 9. What do you get? The number is 778. 100 is subtracted from this, since 100 grams of acid were initially taken. This makes 668 milliliters of water. This amount is mixed with 100 g of vinegar. The result is a whole bottle of 9% solution.

Although, it can be done even simpler. Many people are interested in how to make vinegar from acetic acid. Easily! The main thing is to remember that for one part of a 70% solution you need to take 7 parts of water.