.
O

//
The -C group of atoms is called a carboxyl group or carboxyl.
\

Oh
Organic acids containing one carboxyl group in the molecule are monobasic. The general formula for these acids is RCOOH.

Carboxylic acids containing two carboxyl groups are called dibasic acids. These include, for example, oxalic and succinic acids.

There are also polybasic carboxylic acids containing more than two carboxyl groups. These include, for example, tribasic citric acid. Depending on the nature of the hydrocarbon radical, carboxylic acids are divided into saturated, unsaturated, aromatic.

Limiting, or saturated, carboxylic acids are, for example, propanoic (propionic) acid or succinic acid already familiar to us.

Obviously, saturated carboxylic acids do not contain P-bonds in the hydrocarbon radical.

In molecules of unsaturated carboxylic acids, the carboxyl group is linked to an unsaturated, unsaturated hydrocarbon radical, for example, in molecules of acrylic (propenoic) CH2=CH-COOH or oleic CH3-(CH2)7-CH=CH-(CH2)7-COOH and other acids.

As can be seen from the formula of benzoic acid, it is aromatic, as it contains an aromatic (benzene) ring in the molecule.

Nomenclature and isomerism

We have already considered the general principles for the formation of the names of carboxylic acids, as well as other organic compounds. Let us dwell in more detail on the nomenclature of mono- and dibasic carboxylic acids. The name of a carboxylic acid is formed from the name of the corresponding alkane (an alkane with the same number of carbon atoms in the molecule) with the addition of the suffix -ov, the ending -aya and the word acid. The numbering of carbon atoms begins with the carboxyl group. For example:

Many acids also have historically established, or trivial, names (Table 6).

After the first acquaintance with the diverse and interesting world of organic acids, let us consider in more detail the limiting monobasic carboxylic acids.

It is clear that the composition of these acids will be reflected by the general formula C n H 2n O2, or C n H 2n +1 COOH, or RCOOH.

Physical properties of saturated monobasic carboxylic acids

Lower acids, i.e., acids with a relatively small molecular weight, containing up to four carbon atoms in a molecule, are liquids with a characteristic pungent odor (remember the smell of acetic acid). Acids containing from 4 to 9 carbon atoms are viscous oily liquids with an unpleasant odor; containing more than 9 carbon atoms in a molecule - solids that do not dissolve in water. The boiling points of limiting monobasic carboxylic acids increase with an increase in the number of carbon atoms in the molecule and, consequently, with an increase in the relative molecular weight. So, for example, the boiling point of formic acid is 101 °C, acetic acid - 118 °C, propionic acid - 141 °C.

The simplest carboxylic acid, formic HCOOH, having a small relative molecular weight (46), under normal conditions is a liquid with a boiling point of 100.8 °C. At the same time, butane (MR(C4H10) = 58) under the same conditions is gaseous and has a boiling point of -0.5 °C. This discrepancy between boiling points and relative molecular weights is explained by the formation of carboxylic acid dimers, in which two acid molecules are linked by two hydrogen bonds. The occurrence of hydrogen bonds becomes clear when considering the structure of carboxylic acid molecules.

Molecules of saturated monobasic carboxylic acids contain a polar group of atoms - carboxyl (think about what causes the polarity of this functional group) and an almost non-polar hydrocarbon radical. The carboxyl group is attracted to water molecules, forming hydrogen bonds with them.

Formic and acetic acids are infinitely soluble in water. Obviously, with an increase in the number of atoms in the hydrocarbon radical, the solubility of carboxylic acids decreases.

Knowing the composition and structure of the molecules of carboxylic acids, it will not be difficult for us to understand and explain the chemical properties of these substances.

Chemical properties

The general properties characteristic of the class of acids (both organic and inorganic) are due to the presence in the molecules of a hydroxyl group containing a strongly polar bond between hydrogen and oxygen atoms. These properties are well known to you. Let us consider them again using the example of water-soluble organic acids.

1. Dissociation with the formation of hydrogen cations and anions of the acid residue. More precisely, this process describes an equation that takes into account the participation of water molecules in it.

The equilibrium of dissociation of carboxylic acids is shifted to the left, the vast majority of them are weak electrolytes. Nevertheless, the sour taste, for example, of formic and acetic acids is explained by the dissociation into hydrogen cations and anions of acidic residues.

Obviously, the presence of “acidic” hydrogen, i.e., the hydrogen of the carboxyl group, in the molecules of carboxylic acids also determines other characteristic properties.

2. Interaction with metals standing in the electrochemical series of voltages up to hydrogen. For example, iron reduces hydrogen from acetic acid:

2CH3-COOH + Fe -> (CHgCOO)2Fe + H2

3. Interaction with basic oxides to form salt and water:

2R-COOH + CaO -> (R-COO) 2Ca + H20

4. Interaction with metal hydroxides to form salt and water (neutralization reaction):

R-COOH + NaOH -> R-COONa + H20 3R-COOH + Ca(OH)2 -> (R-COO)2Ca + 2H20

5. Interaction with salts of weaker acids, with the formation of the latter. Thus, acetic acid displaces stearic acid from sodium stearate and carbonic acid from potassium carbonate.

6. The interaction of carboxylic acids with alcohols to form esters is the esterification reaction already known to you (one of the most important reactions characteristic of carboxylic acids). The interaction of carboxylic acids with alcohols is catalyzed by hydrogen cations.

The esterification reaction is reversible. The equilibrium shifts towards ester formation in the presence of dewatering agents and removal of ether from the reaction mixture.

In the reverse reaction of esterification, which is called ester hydrolysis (reaction of an ester with water), an acid and an alcohol are formed. Obviously, polyhydric alcohols, such as glycerol, can also react with carboxylic acids, i.e., enter into an esterification reaction:

All carboxylic acids (except formic), along with a carboxyl group, contain a hydrocarbon residue in their molecules. Of course, this cannot but affect the properties of acids, which are determined by the nature of the hydrocarbon residue.

7. Multiple bond addition reactions - unsaturated carboxylic acids enter into them; for example, the hydrogen addition reaction is hydrogenation. When oleic acid is hydrogenated, saturated stearic acid is formed.

Unsaturated carboxylic acids, like other unsaturated compounds, add halogens to the double bond. For example, acrylic acid decolorizes bromine water.

8. Substitution reactions (with halogens) - saturated carboxylic acids are able to enter into it; for example, by reacting acetic acid with chlorine, various chlorine derivatives of acids can be obtained:

When halogenating carboxylic acids containing more than one carbon atom in the hydrocarbon residue, the formation of products with different positions of the halogen in the molecule is possible. When the reaction proceeds according to the free radical mechanism, any hydrogen atoms in the hydrocarbon residue can be replaced. If the reaction is carried out in the presence of small amounts of red phosphorus, then it proceeds selectively - hydrogen is replaced only in a-position (at the carbon atom closest to the functional group) in the acid molecule. You will learn the reasons for this selectivity when studying chemistry at a higher educational institution.

Carboxylic acids form various functional derivatives upon substitution of the hydroxyl group. Upon hydrolysis of these derivatives, a carboxylic acid is again formed from them.

The carboxylic acid chloride can be obtained by treating the acid with phosphorus(III) chloride or thionyl chloride (SOCl 2). Anhydrides of carboxylic acids are obtained by the interaction of anhydride chlorides with salts of carboxylic acids. Esters are formed as a result of the esterification of carboxylic acids with alcohols. Etherification is catalyzed by inorganic acids.

This reaction is initiated by the protonation of the carboxyl group - the interaction of the hydrogen cation (proton) with the lone electron pair of the oxygen atom. The protonation of the carboxyl group entails an increase in the positive charge on the carbon atom in it:

How to get

Carboxylic acids can be obtained by oxidation of primary alcohols and aldehydes.

Aromatic carboxylic acids are formed from the oxidation of benzene homologues.

Hydrolysis of various carboxylic acid derivatives also results in acids. So, during the hydrolysis of an ester, an alcohol and a carboxylic acid are formed. As mentioned above, the esterification and hydrolysis reactions catalyzed by acid are reversible. The hydrolysis of the ester under the action of an aqueous solution of alkali proceeds irreversibly, in this case, not an acid, but its salt is formed from the ester. In the hydrolysis of nitriles, amides are first formed, which are then converted to acids. Carboxylic acids are formed by the interaction of organomagnesium compounds with carbon monoxide(IV).

Individual representatives of carboxylic acids and their significance

Formic (methane) acid HCOOH is a liquid with a pungent odor and a boiling point of 100.8 ° C, it is highly soluble in water. Formic acid is poisonous and causes burns if it comes into contact with the skin! The stinging fluid secreted by ants contains this acid. Formic acid has a disinfectant property and therefore finds its application in the food, leather and pharmaceutical industries, and medicine. It is also used in dyeing textiles and paper.

Acetic (ethanoic) acid CH3COOH is a colorless liquid with a characteristic pungent odor, miscible with water in any ratio. Aqueous solutions of acetic acid are sold under the name of vinegar (3-5% solution) and vinegar essence (70-80% solution) and are widely used in the food industry. Acetic acid is a good solvent for many organic substances and is therefore used in dyeing, in the leather industry, and in the paint and varnish industry. In addition, acetic acid is a raw material for the production of many technically important organic compounds: for example, it is used to obtain substances used to control weeds - herbicides.

Acetic acid is the main component of wine vinegar, the characteristic smell of which is due to it. It is a product of the oxidation of ethanol and is formed from it when wine is stored in air.

The most important representatives of the highest limiting monobasic acids are palmitic C15H31COOH and stearic C17H35COOH acids. Unlike lower acids, these substances are solid, poorly soluble in water.

However, their salts - stearates and palmitates - are highly soluble and have a detergent effect, which is why they are also called soaps. It is clear that these substances are produced on a large scale.

Of the unsaturated higher carboxylic acids, oleic acid C17H33COOH, or (CH2)7COOH, is of the greatest importance. It is an oil-like liquid, tasteless and odorless. Its salts are widely used in technology.

The simplest representative of dibasic carboxylic acids is oxalic (ethanedioic) acid HOOC-COOH, salts of which are found in many plants, for example, in sorrel and oxalis. Oxalic acid is a colorless crystalline substance, highly soluble in water. It is used in the polishing of metals, in the woodworking and leather industries.

1. Unsaturated elaidic acid С17Н33СООН is a trans-isomer of oleic acid. Write the structural formula of this substance.

2. Write an equation for the hydrogenation of oleic acid. Name the product of this reaction.

3. Write an equation for the combustion reaction of stearic acid. What volume of oxygen and air (N.S.) will be required to burn 568 g of stearic acid?

4. A mixture of solid fatty acids - palmitic and stearic - is called stearin (stearin candles are made from it). What volume of air (n.a.) will be required to burn a 200 gram stearin candle if the stearin contains equal masses of palmitic and stearic acids? What volume of carbon dioxide (n.a.) and mass of water are formed in this case?

5. Solve the previous problem, provided that the candle contains equal amounts (the same number of moles) of stearic and palmitic acids.

6. To remove rust stains, they are treated with a solution of acetic acid. Make up the molecular and ionic equations of the reactions taking place in this case, given that rust contains iron (III) oxide and hydroxide - Fe2O3 and Fe (OH) 3. Why are such stains not removed with water? Why do they disappear when treated with an acid solution?

7. The food (drinking) soda MaHC03 added to the yeast-free dough is preliminarily “quenched” with acetic acid. Do this reaction at home and make up its equation, knowing that carbonic acid is weaker than acetic acid. Explain the formation of foam.

8. Knowing that chlorine is more electronegative than carbon, arrange the following acids: acetic, propionic, chloroacetic, dichloroacetic and trichloroacetic acids in order of increasing acidic properties. Justify your result.

9. How can one explain that formic acid enters into a "silver mirror" reaction? Write an equation for this reaction. What gas can be released in this case?

10. In the interaction of 3 g of saturated monobasic carboxylic acid with an excess of magnesium, 560 ml (n.a.) of hydrogen were released. Determine the formula of the acid.

11. Give reaction equations that can be used to describe the chemical properties of acetic acid. Name the products of these reactions.

12. Suggest a simple laboratory method that can be used to recognize propanoic and acrylic acids.

13. Write an equation for the reaction of obtaining methyl formate - an ester of methanol and formic acid. Under what conditions should this reaction be carried out?

14. Make structural formulas of substances having the composition С3Н602. What classes of substances can they be assigned to? Give the equations of the reactions characteristic of each of them.

15. Substance A - an isomer of acetic acid - does not dissolve in water, but can be hydrolyzed. What is the structural formula of substance A? Name the products of its hydrolysis.

16. Make the structural formulas of the following substances:

a) methyl acetate;
b) oxalic acid;
c) formic acid;
d) dichloroacetic acid;
e) magnesium acetate;
e) ethyl acetate;
g) ethyl formate;
h) acrylic acid.

17*. A sample of the limiting monobasic organic acid weighing 3.7 g was neutralized with an aqueous solution of sodium bicarbonate. By passing the evolved gas through lime water, 5.0 g of a precipitate was obtained. What acid was taken and what was the volume of the released gas?

carboxylic acids in nature

Carboxylic acids are very common in nature. They are found in fruits and plants. They are present in needles, sweat, urine and nettle juice. You know, it turns out that most of the acids form esters that have odors. So the smell of lactic acid, which is contained in human sweat, attracts mosquitoes, they feel it at quite a considerable distance. Therefore, no matter how much you try to drive away the annoying mosquito, he still feels good about his victim. In addition to human sweat, lactic acid is found in pickles and sauerkraut.

And female monkeys, in order to attract a male, release acetic and propionic acid. The sensitive, canine nose is able to smell butyric acid, which has a concentration of 10–18 g/cm3.

Many plant species are able to secrete acetic and butyric acid. And some weeds take advantage of this and release substances, eliminate their competitors, suppressing their growth, and sometimes causing their death.

The Indians also used acid. To destroy the enemy, they moistened the arrows with a deadly poison, which turned out to be a derivative of acetic acid.

And here a natural question arises, do acids pose a danger to human health? Indeed, oxalic acid, which is widespread in nature, which is found in sorrel, oranges, currants and raspberries, for some reason has not found application in the food industry. It turns out that oxalic acid is two hundred times stronger than acetic acid, and can even corrode dishes, and its salts, accumulating in the human body, form stones.

Acids are widely used in all spheres of human life. They are used in medicine, cosmetology, food industry, agriculture and used for domestic needs.

For medical purposes, organic acids such as lactic, tartaric, and ascorbic acids are used. Probably, each of you used vitamin C to strengthen the body - this is just ascorbic acid. It not only helps to strengthen the immune system, but also has the ability to remove carcinogens and toxins from the body. Lactic acid is used for cauterization, as it is highly hygroscopic. But tartaric acid acts as a mild laxative, as an antidote for alkali poisoning and as a component necessary for the preparation of plasma during blood transfusion.

But fans of cosmetic procedures should be aware that the fruit acids contained in citrus fruits have a beneficial effect on the skin, as they penetrate deep into the skin and can accelerate the process of skin renewal. In addition, the smell of citrus fruits has a tonic effect on the nervous system.

Have you noticed that berries such as cranberries and lingonberries are stored for a long time and remain fresh. Do you know why? It turns out that they contain benzoic acid, which is an excellent preservative.

But in agriculture, succinic acid has found wide application, since it can be used to increase the yield of cultivated plants. It is also able to stimulate the growth of plants and accelerate their development.

In table. 19.10 lists some organic compounds related to carboxylic acids. A characteristic feature of carboxylic acids is the presence of a carboxylic acid in them.

Table 19.10. carboxylic acids

(see scan)

functional group. The carboxyl group consists of a carbonyl group linked to a hydroxyl group. Organic acids with one carboxyl group are called monocarboxylic acids. Their systematic names have the suffix -ov(aya). Organic acids with two carboxyl groups are called dicarboxylic acids. Their systematic names have the suffix -div(aya).

Saturated aliphatic monocarboxylic acids form a homologous series, which is characterized by the general formula. Unsaturated aliphatic dicarboxylic acids can exist in the form of various geometric isomers (see Section 17.2).

Physical properties

The lower members of the homologous series of saturated monocarboxylic acids under normal conditions are liquids with a characteristic pungent odor. For example, ethanoic (acetic) acid has a characteristic "acetic" smell. Anhydrous acetic acid is a liquid at room temperature. It freezes when it turns into an icy substance called glacial acetic acid.

All dicarboxylic acids listed in table. 19.10, at room temperature are white crystalline solids. The lower members of the series of monocarboxylic and dicarboxylic acids are soluble in water. The solubility of carboxylic acids decreases as their relative molecular weight increases.

In the liquid state and in non-aqueous solutions, the molecules of monocarboxylic acids dimerize as a result of the formation of hydrogen bonds between them:

Hydrogen bonds are stronger in carboxylic acids than in alcohols. This is due to the high polarity of the carboxyl group, due to the pulling of electrons from the hydrogen atom towards the carbonyl oxygen atom:

As a result, carboxylic acids have relatively high boiling points (Table 19.11).

Table 19.11. Boiling points of acetic acid and alcohols with close relative molecular weights

Laboratory methods of obtaining

Monocarboxylic acids can be obtained from primary alcohols and aldehydes by oxidation with an acidified potassium dichromate solution, taken in excess:

Monocarboxylic acids and their salts can be obtained by hydrolysis of nitriles or amides:

The preparation of carboxylic acids by reaction with Grignard reagents and carbon dioxide is described in Sec. 19.1.

Benzoic acid can be obtained by oxidation of the methyl side chain of methylbenzene (see Section 18.2).

In addition, benzoic acid can be obtained from benzaldehyde using the Cannisharo reaction. In this reaction, benzaldehyde is treated with 40-60% sodium hydroxide solution at room temperature. Simultaneous oxidation and reduction leads to the formation of benzoic acid and, accordingly, phenyl methanol:

Oxidation

The Cannizzaro reaction is typical for aldehydes that do not have -hydrogen atoms. This is the name of the hydrogen atoms attached to the carbon atom adjacent to the aldehyde group:

Since methanal does not have -hydrogen atoms, it can react with Cannizzaro. Aldehydes containing at least one α-hydrogen atom undergo acid-catalyzed aldol condensation in the presence of sodium hydroxide solution (see above).

Chemical properties

Although the carboxyl group contains a carbonyl group, carboxylic acids do not undergo some of the reactions that are characteristic of aldehydes and ketones. For example, they do not enter into addition or condensation reactions. This is because the atom

carbon in the carboxyl group has a smaller positive charge than in the aldehyde or keto group.

Acidity. Pulling the electron density away from the carboxyl hydrogen atom weakens the O-H bond. As a result, the carboxyl group is able to split off (lose) a proton. Therefore, monocarboxylic acids behave like monobasic acids. In aqueous solutions of these acids, the following equilibrium is established:

The carboxylate ion can be considered as a hybrid of two resonance structures:

Otherwise, it can be thought of as

The delocalization of an electron between the atoms of the carboxylate group stabilizes the carboxylate ion. Therefore, carboxylic acids are much more acidic than alcohols. However, due to the covalent nature of the carboxylic acid molecules, the above equilibrium is strongly shifted to the left. Thus, carboxylic acids are weak acids. For example, ethanoic (acetic) acid is characterized by an acidity constant

The substituents present in the carboxylic acid molecule strongly influence its acidity due to their inductive effect. Substituents such as chlorine pull electron density towards themselves and therefore cause a negative inductive effect Pulling electron density away from the carboxyl hydrogen atom leads to an increase in the acidity of the carboxylic acid. In contrast, substituents such as alkyl groups have electron-donating properties and create a positive inductive effect. They weaken the carboxylic acid:

The influence of substituents on the acidity of carboxylic acids is clearly manifested in the values ​​for a number of acids indicated in Table. 19.12.

Table 19.12. Values ​​of carboxylic acids

Salt formation. Carboxylic acids have all the properties of ordinary acids. They react with reactive metals, bases, alkalis, carbonates and bicarbonates, forming the corresponding salts (Table 19.13). The reactions indicated in this table are also characteristic of soluble and insoluble carboxylic acids.

Like other salts of weak acids, carboxylate salts (salts of carboxylic acids) react with mineral acids taken in excess, forming the original carboxylic acids. For example, when a sodium hydroxide solution is added to a suspension of insoluble benzoic acid in water, the acid dissolves due to the formation of sodium benzoate. If sulfuric acid is then added to the resulting solution, benzoic acid precipitates:

Table 19.13. Formation of salts from carboxylic acids

Etherification. When a mixture of carboxylic acid and alcohol is heated in the presence of a concentrated mineral acid, an ester is formed. This process, called esterification, requires the breakdown of alcohol molecules. In this case, there are two possibilities.

1. Hydrogen alkoxy splitting. In this case, the alcohol oxygen atom (from the hydroxyl group) enters the molecule of the resulting ether:

2. Alkylhydroxyl cleavage. In this type of splitting, an alcohol oxygen atom enters a water molecule:

Which of these cases is actually implemented can be determined experimentally by performing esterification using an alcohol containing the 180 isotope (see Section 1.3), i.e. using an isotope label. Determination of the relative molecular weight of the resulting ether using mass spectrometry shows whether the isotopic label oxygen-18 is present in it. In this way, it was found that esterification with the participation of primary alcohols leads to the formation of labeled esters:

This shows that the methanol molecule undergoes methoxy-hydrogen cleavage during the reaction under consideration.

Halogenation. Carboxylic acids react with phosphorus pentachloride and sulfur oxide dichloride to form acid chlorides of the corresponding acids. For example

Both benzoyl chloride and phosphorus oxide trichloride are liquids that must be separated from each other. Therefore, for the chlorination of carboxylic acids, it is more convenient to use sulfur oxide dichloride: this makes it easy to remove gaseous hydrogen chloride and sulfur dioxide from liquid carboxylic acid chloride:

By blowing chlorine through boiling acetic acid in the presence of catalysts such as red phosphorus or iodine, and under the action of sunlight

monochloroethanoic (monochloroacetic) acid is formed:

Further chlorination leads to the formation of dimixed and trisubstituted products:

Recovery. When interacting with lithium in dry diethyl ether, carboxylic acids can be reduced to the corresponding alcohols. First, an alkoxide intermediate is formed, the hydrolysis of which leads to the formation of an alcohol:

Carboxylic acids are not reduced by many common reducing agents. These acids cannot be immediately reduced to the corresponding aldehydes.

Oxidation. With the exception of methane (formic) and ethanoic (acetic) acids, other carboxylic acids are oxidized with difficulty. Formic acid and its salts (formates) are oxidized with potassium permanganate. Formic acid is capable of reducing Fehling's reagent and, when heated in a mixture with an aqueous ammonia solution of silver nitrate, forms a "silver mirror". When formic acid is oxidized, carbon dioxide and water are formed:

Ethandioic (oxalic) acid is also oxidized by potassium permanganate, forming carbon dioxide and water:

Dehydration. Distillation of a carboxylic acid with a dehydrating agent, such as an oxide, leads to the elimination of a water molecule from two acid molecules and the formation of carboxylic acid anhydride:

Formic and oxalic acids are also exceptions in this case. Dehydration of formic acid or its potassium or sodium salt with concentrated sulfuric acid leads to the formation of carbon monoxide and

Dehydration of sodium methanoate (formate) with concentrated sulfuric acid is a common laboratory method for producing carbon monoxide. Dehydration of oxalic acid with hot concentrated sulfuric acid results in a mixture of carbon monoxide and carbon dioxide:

Carboxylates

Sodium and potassium salts of carboxylic acids are white crystalline substances. They readily dissolve in water, forming strong electrolytes.

Electrolysis of sodium or potassium carboxylate salts dissolved in a water-methanol mixture leads to the formation of alkanes and carbon dioxide at the anode and hydrogen at the cathode.

On the anode:

On the cathode:

This method of obtaining alkanes is called Kolbe's electrochemical synthesis.

The formation of alkanes also occurs when a mixture of sodium or potassium carboxylates is heated with sodium hydroxide or soda lime. (Soda lime is a mixture of sodium hydroxide and calcium hydroxide.) This method is used, for example, to produce methane in the laboratory:

Aromatic carboxylates of sodium or potassium under similar conditions form arenes:

When a mixture of sodium carboxylates with acid chlorides is heated, anhydrides of the corresponding carboxylic acids are formed:

Calcium carboxylates are also white crystalline substances and, as a rule, are soluble in water. When heated, they form

low yield of the corresponding ketones:

When a mixture of calcium carboxylates and calcium formate is heated, an aldehyde is formed:

Ammonium salts of carboxylic acids are also white crystalline substances, soluble in water. When heated strongly, they form the corresponding amides:

CARBOXIC ACIDS.

Carboxylic acids are derivatives of hydrocarbons, the molecule of which contains one or more carboxyl groups.

General formula limit monobasic carboxylic acids: FROM n H 2n O 2

Classification of carboxylic acids.

1. According to the number of carboxyl groups:

Single base (monocarbon)

Polybasic (dicarboxylic, tricarboxylic, etc.).

1. 
   By the nature of the hydrocarbon radical:

Limit CH 3 -CH 2 -CH 2 -COOH; butanoic acid.

- unsaturated CH 2 =CH-CH 2 -COOH; butenoic acid.
- aromatic

para-methylbenzoic acid
NAMES OF CARBOXY ACIDS.

Name			Formula acids
acids		its salt and (ethers)
formic	methane	formate	HCOOH
acetic	ethane	acetate	CH3COOH
propionic	propane	propionate	CH 3 CH 2 COOH
oily	butane	butyrate	CH 3 (CH 2) 2 COOH
valerian	pentane	valerate	CH 3 (CH 2) 3 COOH
kapron	hexane	hexanate	CH 3 (CH 2) 4 COOH
palmitic	hexadecanoic	palmitate	C 15 H 31 COOH
stearic	octadecanoic	stearate	C 17 H 35 COOH
acrylic	propene	acrylate	CH 2 \u003d CH-COOH
oleic	cis-9-octadecenoic	oleate	CH 3 (CH 2) 7 CH \u003d CH (CH 2) 7 COOH
benzoic	benzoic	benzoate	C 6 H 5 -COOH
oxalic	ethanedioic	oxalate	NOOS - COOH

Isomerism of carboxylic acids.

1. Isomerism of the carbon chain. Begins with butanoic acid (FROM 3 H 7 UNSD) , which exists in the form of two isomers: butyric (butanoic) and isobutyric (2-methylpropanoic) acids.
2. Isomerism of the position of a multiple bond in unsaturated acids, for example:

CH 2 \u003d CH-CH 2 -COOH CH 3 -CH \u003d CH-COOH

Butene-3-oic acid Butene-2-oic acid

(vinylacetic acid) (crotonic acid)
3. Cis-, trans-isomerism in unsaturated acids, for example:

4. Interclass isomerism: Carboxylic acids are isomeric to esters:

Acetic acid CH 3 -COOH and methyl formate H-COOSH 3

5. isomerism positions of functional groups at heterofunctional acids .

For example, there are three isomers of chlorobutyric acid: 2-chlorobutanoic, 3-chlorobutanoic and 4-chlorobutanoic.

STRUCTURE OF THE CARBOXY GROUP.

The carboxyl group combines two functional groups - carbonyl and hydroxyl, mutually influencing each other

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

Solubility in water and high boiling points of acids are due to the formation intermolecular hydrogen bonds. As the molecular weight increases, the solubility of acids in water decreases.

DERIVATIVES OF CARBOXY ACID – in them, the hydroxo group is replaced by some other groups. All of them form carboxylic acids upon hydrolysis.

salt	Esters	Acid halides	Anhydrides	Amides.

OBTAINING CARBOXIC ACIDS.

1. Oxidation of alcohols in harsh conditions - with a solution of potassium permanganate or dichromate in an acidic medium when heated.
2.Oxidation of aldehydes: potassium permanganate or dichromate solution in an acid medium when heated, silver mirror reaction, copper hydroxide when heated.
3. Alkaline hydrolysis of trichlorides:	R-CCl 3 + 3NaOH  + 3NaCl unstable substance  RCOOH + H2O
4. Hydrolysis of esters.	R-COOR 1 + KOH  RCOOK + R 1 OH RCOOK + HCl  R-COOH + KCl
5. Hydrolysis of nitriles, anhydrides, salts.	1) nitrile: R-CN + 2H 2 O - (H +)  RCOOH 2) anhydride: (R-COO) 2 O + H 2 O  2RCOOH 3) sodium salt: R-COONa + HClR-COOH + NaCl
6. Interaction of the Grignard reagent with CO 2:	R-MgBr + CO 2  R-COO-MgBr R-COO-MgBr -(+H 2 O) R-COOH +Mg(OH)Br
7. Formic acid receive heating carbon monoxide (II) with sodium hydroxide under pressure:	NaOH + CO –(200 o C,p) HCOONa 2HCOONa + H 2 SO 4  2HCOOH + Na 2 SO 4
8. Acetic acid receive catalytic oxidation of butane:	2C 4 H 10 + 5O 2  4CH 3 -COOH + 2H 2 O
9. To receive benzoic acid can be used oxidation of monosubstituted benzene homologues acidic solution of potassium permanganate:	5C 6 H 5 –CH 3 +6KMnO 4 +9H 2 SO 4 5C 6 H 5 -COOH + 3K 2 SO 4 + MnSO 4 + 14H 2 O

CHEMICAL PROPERTIES OF CARBOXY ACIDS.

1. Acid properties - substitution of the H atom in the carboxyl group for a metal or ammonium ion.

1.Interaction with metals	2CH 3 COOH + Ca  (CH 3 COO) 2 Ca + H 2 calcium acetate
2. Interaction with metal oxides	2CH 3 COOH + BaO  (CH 3 COO) 2 Ba + H 2 O
3. Neutralization reaction with metal hydroxides	2CH 3 COOH + Cu (OH) 2  (CH 3 COO) 2 Cu + 2H 2 O
4. Interaction with salts of weaker and volatile (or insoluble) acids	2CH 3 COOH + CaCO 3  (CH 3 COO) 2 Ca + H 2 O + CO 2
4*. Qualitative reaction to carboxylic acids: interaction with soda (sodium bicarbonate) or other carbonates and bicarbonates. As a result, carbon dioxide is released. 2CH 3 COOH + Na 2 CO 3 à 2CH 3 COONa + H 2 O + CO 2 
2. Substitution of the hydroxyl group:
5.Esterification reaction
6. Formation of halogen anhydrides - with the help of phosphorus (III) and (V) chlorides.
7. Formation of amides:
8. Obtaining anhydrides.	With the help of P 2 O 5, carboxylic acid can be dehydrated - the result is an anhydride. 2CH 3 - COOH + R 2 O 5  (CH 3 CO) 2 O + HPO 3
3. Substitution of a hydrogen atom at the carbon atom closest to the carboxyl group (-carbon atom)
9.Halogenation of acids- the reaction takes place in the presence of red phosphorus or in the light.	CH 3 -COOH + Br 2 - (P cr)  CH 2 -COOH + HBr
Features of formic acid.
1. Decomposition upon heating.	H-COOH - (H 2 SO 4 conc, t)  CO + H 2 O
2. The reaction of the silver mirror and with copper (II) hydroxide - formic acid exhibits the properties of aldehydes.	H-COOH + 2OH (NH 4) 2 CO 3 +2 Ag + 2NH 3 + H 2 O H-COOH + Cu(OH) 2 –t CO 2 + Cu 2 O + H 2 O
3. Oxidation with chlorine and bromine, as well as nitric acid.	H-COOH + Cl 2  CO 2 + 2HCl
Features of benzoic acid.
1. Decomposition upon heating - decarboxylation.	P When benzoic acid is heated, it decomposes into benzene and carbon dioxide:
2. Substitution reactions in the aromatic ring.	The carboxyl group is an electron-withdrawing group, it reduces the electron density of the benzene ring and is meta orientator. + HNO 3 - (H 2 SO 4)  + H 2 O
Features of oxalic acid.
1. Decomposition when heated
2. Oxidation with potassium permanganate.
Features of unsaturated acids (acrylic and oleic).
1. Addition reactions.	The addition of water and hydrogen bromide to acrylic acid occurs against Markovnikov's rule, because the carboxyl group is an electron-withdrawing group: CH 2 \u003d CH-COOH + HBr  Br-CH 2 -CH 2 -COOH Halogens and hydrogen can also be added to unsaturated acids: C 17 H 33 -COOH + H 2  C 17 H 35 -COOH (stearic)
2. Oxidation reactions	With the mild oxidation of acrylic acid, 2 hydroxo groups are formed: 3CH 2 \u003d CH-COOH + 2KMnO 4 + 2H 2 O  2CH 2 (OH) -CH (OH) -COOK + CH 2 (OH) -CH (OH) -COOH + 2MnO 2

Properties of salts of carboxylic acids.

Properties of acid halides

ESTERS

– these are compounds containing a carboxyl group linked to two alkyl radicals.

The general formula of esters is the same as for carboxylic acids: C n H 2 n O 2

NOMENCLATURE OF ESTERS. The names of esters are determined by the names acid and alcohol from which they are formed.

OBTAINING COMPLEX ESTERS.

1) Esters can be obtained when interactingcarboxylic acids with alcohols(esterification reaction ). The catalysts are mineral acids.

2) Esters of phenols cannot be obtained by esterification, to obtain them using the reaction phenolate with acid halide:

C 6 H 5 -O - Na + + C 2 H 5 -C \u003d O  NaCl + C 6 H 5 -O-C \u003d O

Cl C 2 H 5

Phenyl ester of propanoic acid (phenylpropanoate)

Types of isomerism of esters.

1. isomerism carbon chain begins at the acid residue with butanoic acid, at the alcohol residue - with propyl alcohol, for example, ethyl isobutanoate, propyl acetate and isopropyl acetate are isomeric.

2. isomerismester position -CO-O-. This type of isomerism begins with esters containing at least 4 carbon atoms, such as ethyl acetate and methyl propionate.

3. Interclass isomerism with carboxylic acids.
PROPERTIES OF COMPLEX ETHERS.
1. Hydrolysis of esters.

The esterification reaction is reversible. The reverse process - the splitting of an ester by the action of water to form a carboxylic acid and an alcohol - is called ester hydrolysis.

Acid hydrolysis reversible:

Alkaline hydrolysis is irreversible:

This reaction is called saponification ester.

2. recovery reaction. The reduction of esters with hydrogen leads to the formation of two alcohols:

Carboxylic acids are derivatives of hydrocarbons, the molecule of which contains one or more carboxyl groups.

The general formula of limiting monobasic carboxylic acids: FROM n H 2n O 2

Classification of carboxylic acids.

1. According to the number of carboxyl groups:

Single base (monocarbon)

Polybasic (dicarboxylic, tricarboxylic, etc.).

By the nature of the hydrocarbon radical:

Limit CH 3 -CH 2 -CH 2 -COOH; butanoic acid.

Unlimited CH 2 =CH-CH 2 -COOH; butenoic acid.

aromatic

para-methylbenzoic acid

Names of carboxylic acids.

Name
		its salt and
formic	methane
acetic	ethane
propionic	propane	propionate
oily	butane		CH 3 (CH 2) 2 COOH
valerian	pentane		CH 3 (CH 2) 3 COOH
kapron	hexane	hexanate	CH 3 (CH 2) 4 COOH
palmitic	hexadecanoic	palmitate	C 15 H 31 COOH
stearic	octadecanoic		C 17 H 35 COOH
acrylic	propene
oleic			CH 3 (CH 2) 7 CH \u003d CH (CH 2) 7 COOH
benzoic	benzoic
oxalic	ethanedioic		NOOS - COOH

Isomerism of carboxylic acids.

1. Isomerism of the carbon chain. Begins with butanoic acid (FROM 3 H 7 UNSD) , which exists in the form of two isomers: butyric (butanoic) and isobutyric (2-methylpropanoic) acids.

2. Isomerism of the position of a multiple bond in unsaturated acids, for example:

CH 2 =CH-CH 2 -COOH CH 3 -CH=CH-COOH

Butene-3-oic acid Butene-2-oic acid

(vinylacetic acid) (crotonic acid)

3. Cis-, trans-isomerism in unsaturated acids, for example:

4. Interclass isomerism: Carboxylic acids are isomeric to esters:

Acetic acid CH 3 -COOH and methyl formate H-COOSH 3

5. isomerismpositions of functional groups at heterofunctional acids .

For example, there are three isomers of chlorobutyric acid: 2-chlorobutanoic, 3-chlorobutanoic, and 4-chlorobutanoic.

The structure of the carboxyl group.

The carboxyl group combines two functional groups - carbonyl and hydroxyl, mutually influencing each other

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

Solubility in water and high boiling points of acids are due to the formation intermolecular hydrogen bonds. As the molecular weight increases, the solubility of acids in water decreases.

DERIVATIVES OF CARBOXY ACID– in them, the hydroxo group is replaced by some other groups. All of them form carboxylic acids upon hydrolysis.

	Esters	Acid halides	Anhydrides

OBTAINING CARBOXIC ACIDS.

1. Oxidation of alcohols in harsh conditions - with a solution of potassium permanganate or dichromate in an acidic medium when heated.
2.Oxidation of aldehydes: potassium permanganate or dichromate solution in an acid medium when heated, silver mirror reaction, copper hydroxide when heated.
3. Alkaline hydrolysis of trichlorides:	R-CCl 3 + 3NaOH  + 3NaCl unstable substance  RCOOH + H2O
4. Hydrolysis of esters.	R-COOR 1 + KOH  RCOOK + R 1 OH RCOOK + HCl  R-COOH + KCl
5. Hydrolysis of nitriles, anhydrides, salts.	1) nitrile: R-CN + 2H 2 O - (H +)  RCOOH 2) anhydride: (R-COO) 2 O + H 2 O  2RCOOH 3) sodium salt: R-COONa + HClR-COOH + NaCl
6. The interaction of the Grignard reagent withSO 2 :	R-MgBr + CO 2  R-COO-MgBr R-COO-MgBr -(+H 2 O) R-COOH +Mg(OH)Br
7. Formic acid receive heating carbon monoxide (II) with sodium hydroxide under pressure:	NaOH + CO –(200 o C,p) HCOONa 2HCOONa + H 2 SO 4  2HCOOH + Na 2 SO 4
8. Acetic acid receive catalytic oxidation of butane:	2C 4 H 10 + 5O 2  4CH 3 -COOH + 2H 2 O
9. To receive benzoic acid can be used oxidation of monosubstituted benzene homologues acidic solution of potassium permanganate:	5C 6 H 5 –CH 3 +6KMnO 4 +9H 2 SO 4 5C 6 H 5 -COOH + 3K 2 SO 4 + MnSO 4 + 14H 2 O

CHEMICAL PROPERTIES OF CARBOXY ACIDS.

Classification

a) By basicity (i.e., the number of carboxyl groups in a molecule):

Monobasic (monocarboxylic) RCOOH; for example:

CH 3 CH 2 CH 2 COOH;

HOOS-CH 2 -COOH propanedioic (malonic) acid

Tribasic (tricarboxylic) R (COOH) 3, etc.

b) According to the structure of the hydrocarbon radical:

Aliphatic

limit; for example: CH 3 CH 2 COOH;

unsaturated; for example: CH 2 \u003d CHCOOH propenoic (acrylic) acid

Alicyclic, for example:

Aromatic, for example:

Limit monocarboxylic acids

(monobasic saturated carboxylic acids) - carboxylic acids in which a saturated hydrocarbon radical is connected to one carboxyl group -COOH. They all have the general formula C n H 2n+1 COOH (n ≥ 0); or CnH 2n O 2 (n≥1)

Nomenclature

The systematic names of monobasic saturated carboxylic acids are given by the name of the corresponding alkane with the addition of the suffix -ovaya and the word acid.

1. HCOOH methane (formic) acid

2. CH 3 COOH ethanoic (acetic) acid

3. CH 3 CH 2 COOH propanoic (propionic) acid

isomerism

The isomerism of the skeleton in the hydrocarbon radical is manifested, starting with butanoic acid, which has two isomers:

Interclass isomerism manifests itself, starting with acetic acid:

CH 3 -COOH acetic acid;

H-COO-CH 3 methyl formate (methyl ester of formic acid);

HO-CH 2 -COH hydroxyethanal (hydroxyacetic aldehyde);

HO-CHO-CH 2 hydroxyethylene oxide.

homologous series

Trivial name	IUPAC name
Formic acid	Methanoic acid
Acetic acid	Ethanoic acid
propionic acid	propanoic acid
Butyric acid	Butanoic acid
Valeric acid	Pentanoic acid
Caproic acid	Hexanoic acid
Enanthic acid	Heptanoic acid
Caprylic acid	Octanoic acid
Pelargonic acid	Nonanoic acid
capric acid	Decanoic acid
Undecylic acid	undecanoic acid
Palmitic acid	Hexadecanic acid
Stearic acid	Octadecanic acid

Acid residues and acid radicals

	acid residue	Acid radical (acyl)
UNSD formic	NSOO- formate
CH 3 COOH acetic	CH 3 SOO- acetate
CH 3 CH 2 COOH propionic	CH 3 CH 2 COO- propionate
CH 3 (CH 2) 2 COOH oily	CH 3 (CH 2) 2 COO- butyrate
CH 3 (CH 2) 3 COOH valerian	CH 3 (CH 2) 3 COO- valeriate
CH 3 (CH 2) 4 COOH kapron	CH 3 (CH 2) 4 COO- capronate

Electronic structure of carboxylic acid molecules

The shift of electron density shown in the formula towards the carbonyl oxygen atom causes a strong polarization of the O-H bond, as a result of which the detachment of the hydrogen atom in the form of a proton is facilitated - in aqueous solutions, the process of acid dissociation occurs:

RCOOH ↔ RCOO - + H +

In the carboxylate ion (RCOO -), p, π-conjugation of the lone pair of electrons of the oxygen atom of the hydroxyl group with p-clouds forming a π-bond takes place, as a result, the π-bond is delocalized and the negative charge is uniformly distributed between the two oxygen atoms:

In this regard, for carboxylic acids, in contrast to aldehydes, addition reactions are not characteristic.

Physical properties

The boiling points of acids are much higher than the boiling points of alcohols and aldehydes with the same number of carbon atoms, which is explained by the formation of cyclic and linear associates between acid molecules due to hydrogen bonds:

Chemical properties

I. Acid properties

The strength of acids decreases in the series:

HCOOH → CH 3 COOH → C 2 H 6 COOH → ...

1. Neutralization reactions

CH 3 COOH + KOH → CH 3 COOK + n 2 O

2. Reactions with basic oxides

2HCOOH + CaO → (HCOO) 2 Ca + H 2 O

3. Reactions with metals

2CH 3 CH 2 COOH + 2Na → 2CH 3 CH 2 COONa + H 2

4. Reactions with salts of weaker acids (including carbonates and bicarbonates)

2CH 3 COOH + Na 2 CO 3 → 2CH 3 COONa + CO 2 + H 2 O

2HCOOH + Mg(HCO 3) 2 → (HCOO) 2 Mg + 2CO 2 + 2H 2 O

(HCOOH + HCO 3 - → HCOO - + CO2 + H2O)

5. Reactions with ammonia

CH 3 COOH + NH 3 → CH 3 COONH 4

II. -OH group substitution

1. Interaction with alcohols (esterification reactions)

2. Interaction with NH 3 when heated (acid amides are formed)

Acid amides hydrolyzed to form acids:

or their salts:

3. Formation of acid halides

Acid chlorides are of the greatest importance. Chlorinating reagents - PCl 3 , PCl 5 , thionyl chloride SOCl 2 .

4. Formation of acid anhydrides (intermolecular dehydration)

Acid anhydrides are also formed by the interaction of acid chlorides with anhydrous salts of carboxylic acids; in this case, mixed anhydrides of various acids can be obtained; for example:

III. Substitution reactions of hydrogen atoms at the α-carbon atom

Features of the structure and properties of formic acid

The structure of the molecule

The formic acid molecule, unlike other carboxylic acids, contains an aldehyde group in its structure.

Chemical properties

Formic acid enters into reactions characteristic of both acids and aldehydes. Showing the properties of an aldehyde, it is easily oxidized to carbonic acid:

In particular, HCOOH is oxidized with an ammonia solution of Ag 2 O and copper (II) hydroxide Сu (OH) 2, i.e. it gives qualitative reactions to the aldehyde group:

When heated with concentrated H 2 SO 4, formic acid decomposes into carbon monoxide (II) and water:

Formic acid is noticeably stronger than other aliphatic acids, since the carboxyl group in it is bonded to a hydrogen atom, and not to an electron-donating alkyl radical.

Methods for obtaining saturated monocarboxylic acids

1. Oxidation of alcohols and aldehydes

The general scheme for the oxidation of alcohols and aldehydes:

KMnO 4 , K 2 Cr 2 O 7 , HNO 3 and other reagents are used as oxidizers.

For example:

5C 2 H 5 OH + 4KMnO 4 + 6H 2 S0 4 → 5CH 3 COOH + 2K 2 SO 4 + 4MnSO 4 + 11H 2 O

2. Hydrolysis of esters

3. Oxidative cleavage of double and triple bonds in alkenes and alkynes

Methods for obtaining HCOOH (specific)

1. Interaction of carbon monoxide (II) with sodium hydroxide

CO + NaOH → HCOONa sodium formate

2HCOONa + H 2 SO 4 → 2HCOOH + Na 2 SO 4

2. Decarboxylation of oxalic acid

Methods for obtaining CH 3 COOH (specific)

1. Catalytic oxidation of butane

2. Synthesis from acetylene

3. Catalytic carbonylation of methanol

4. Acetic acid fermentation of ethanol

This is how food grade acetic acid is obtained.

Obtaining higher carboxylic acids

Hydrolysis of natural fats

Unsaturated monocarboxylic acids

Key Representatives

General formula of alkenoic acids: C n H 2n-1 COOH (n ≥ 2)

CH 2 \u003d CH-COOH propenoic (acrylic) acid

Higher unsaturated acids

The radicals of these acids are part of vegetable oils.

C 17 H 33 COOH - oleic acid, or cis-octadiene-9-oic acid

Trance-isomer of oleic acid is called elaidic acid.

C 17 H 31 COOH - linoleic acid, or cis, cis-octadiene-9,12-oic acid

C 17 H 29 COOH - linolenic acid, or cis, cis, cis-octadecatriene-9,12,15-oic acid

In addition to the general properties of carboxylic acids, unsaturated acids are characterized by addition reactions at multiple bonds in the hydrocarbon radical. So, unsaturated acids, like alkenes, are hydrogenated and decolorize bromine water, for example:

Individual representatives of dicarboxylic acids

Limiting dicarboxylic acids HOOC-R-COOH

HOOC-CH 2 -COOH propanedioic (malonic) acid, (salts and esters - malonates)

HOOC-(CH 2) 2 -COOH butadiic (succinic) acid, (salts and esters - succinates)

HOOC-(CH 2) 3 -COOH pentadiic (glutaric) acid, (salts and esters - glutorates)

HOOC-(CH 2) 4 -COOH hexadioic (adipic) acid, (salts and esters - adipinates)

Features of chemical properties

Dicarboxylic acids are in many ways similar to monocarboxylic acids, but are stronger. For example, oxalic acid is almost 200 times stronger than acetic acid.

Dicarboxylic acids behave like dibasic acids and form two series of salts - acidic and medium:

HOOC-COOH + NaOH → HOOC-COONa + H 2 O

HOOC-COOH + 2NaOH → NaOOC-COONa + 2H 2 O

When heated, oxalic and malonic acids are easily decarboxylated: