The composition of the carboxyl group includes. carboxylic acids

The carboxyl group combines two functional groups - carbonyl and hydroxyl, mutually influencing each other. This influence is transmitted through the conjugation system sp 2 -atoms O–C–O.

The electronic structure of the -COOH group gives carboxylic acids their characteristic chemical and physical properties.

1. The shift of the electron density to the carbonyl oxygen atom causes an additional (compared to alcohols and phenols) polarization of the О–Н bond, which determines the mobility of the hydrogen atom ( acid properties).
In an aqueous solution, carboxylic acids dissociate into ions:

However, carboxylic acids in general are weak acids: in aqueous solutions, their salts are highly hydrolyzed.
Video experience "Carboxylic acids - weak electrolytes".

2. Reduced electron density (δ+) on the carbon atom in the carboxyl group makes it possible for reactions nucleophilic substitution-OH groups.

3. The -COOH group, due to the positive charge on the carbon atom, reduces the electron density on the hydrocarbon radical associated with it, i.e. is in relation to him electron-withdrawing deputy. In the case of saturated acids, the carboxyl group exhibits -I -Effect, and in unsaturated (for example, CH 2 \u003d CH-COOH) and aromatic (C 6 H 5 -COOH) - -I and -M -effects.

4. The carboxyl group, being an electron acceptor, causes additional polarization of the C–H bond in the neighboring (α-) position and increases the mobility of the α-hydrogen atom in substitution reactions at the hydrocarbon radical.
See also "Reaction centers in carboxylic acid molecules".

Hydrogen and oxygen atoms in the -COOH carboxyl group are capable of forming intermolecular hydrogen bonds, which largely determines physical properties carboxylic acids.

Due to the association of molecules, carboxylic acids have high boiling and melting points. Under normal conditions, they exist in a liquid or solid state.

For example, the simplest representative, formic acid HCOOH, is a colorless liquid with bp. 101 ° C, and pure anhydrous acetic acid CH 3 COOH, when cooled to 16.8 ° C, turns into transparent crystals resembling ice (hence its name glacial acid).
Video experience "Ice acetic acid".
The simplest aromatic acid - benzoic C 6 H 5 COOH (mp. 122.4 ° C) - easily sublimes, i.e. changes to the gaseous state without going through the liquid state. When cooled, its vapors sublimate into crystals. This property is used to purify a substance from impurities.
Video experience "Sublimation of benzoic acid".

The solubility of carboxylic acids in water is due to the formation of intermolecular hydrogen bonds with the solvent:

The lower homologues C 1 -C 3 are miscible with water in any ratio. As the hydrocarbon radical increases, the solubility of acids in water decreases. Higher acids such as palmitic C 15 H 31 COOH and stearic C 17 H 35 COOH are colorless solids that are insoluble in water.

carboxylic acids compounds that contain a carboxyl group are called:

Carboxylic acids are distinguished:

monobasic carboxylic acids;
dibasic (dicarboxylic) acids (2 groups UNSD).

Depending on the structure, carboxylic acids are distinguished:

aliphatic;
alicyclic;
aromatic.

Examples of carboxylic acids.

Obtaining carboxylic acids.

1. Oxidation of primary alcohols with potassium permanganate and potassium dichromate:

2. Hydrolysis of halogenated hydrocarbons containing 3 halogen atoms at one carbon atom:

3. Obtaining carboxylic acids from cyanides:

When heated, the nitrile hydrolyzes to form ammonium acetate:

When acidified, acid precipitates:

4. Use of Grignard reagents:

5. Hydrolysis of esters:

6. Hydrolysis of acid anhydrides:

7. Specific methods for obtaining carboxylic acids:

Formic acid is obtained by heating carbon monoxide (II) with powdered sodium hydroxide under pressure:

Acetic acid is obtained by catalytic oxidation of butane with atmospheric oxygen:

Benzoic acid is obtained by oxidation of monosubstituted homologues with a solution of potassium permanganate:

Cannicaro's reaction. Benzaldehyde is treated with 40-60% sodium hydroxide solution at room temperature.

Chemical properties of carboxylic acids.

In an aqueous solution, carboxylic acids dissociate:

The equilibrium is shifted strongly to the left, because carboxylic acids are weak.

Substituents affect acidity through an inductive effect. Such substituents pull the electron density towards themselves and a negative inductive effect (-I) arises on them. Pulling the electron density leads to an increase in the acidity of the acid. Electron donor substituents create a positive inductive charge.

1. Formation of salts. Reaction with basic oxides, salts of weak acids and active metals:

Carboxylic acids are weak, because mineral acids displace them from the corresponding salts:

2. Formation of functional derivatives of carboxylic acids:

3. Esters when an acid is heated with alcohol in the presence of sulfuric acid - an esterification reaction:

4. Formation of amides, nitriles:

3. The properties of acids are determined by the presence of a hydrocarbon radical. If the reaction proceeds in the presence of red phosphorus, it forms the following product:

4. Addition reaction.

8. Decarboxylation. The reaction is carried out by fusing an alkali with an alkali metal salt of a carboxylic acid:

9. Dibasic acid easily splits off CO 2 when heated:

Additional materials on the topic: Carboxylic acids.

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CARBOXY GROUP

carboxy group, carboxyl, - monovalent group

characteristic of carboxylic acids. Consists of carbonyl

and hydroxyl (-OH) groups (hence the name: carb + oxyl).

Big encyclopedic polytechnic dictionary. 2004 .

See what the "CARBOXY GROUP" is in other dictionaries:

- (carboxyl) COOH is a functional monovalent group that is part of carboxylic acids and determines their acidic properties. The structure of the carboxyl group ... Wikipedia

CARBOXYL, CARBOXYL group [carboxylic… + gr. sour] - a monoatomic COOH group characterizing organic, so-called. carboxylic acids, for example, acetic acid CH3COOH A large dictionary of foreign words. Publishing house "IDDK", 2007 ... Dictionary of foreign words of the Russian language

CARBOXY GROUP- (carboxyl), COOH acid group C present in (see); the number of K. g. determines the basicity of the acid ... Great Polytechnic Encyclopedia

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A monovalent gr. COOH, the presence of which determines the affiliation of the org. compounds to carboxylic acids. Example: acetic acid CH3COOH. When hydrogen is replaced by a metal in K. salts are formed, when hydrogen is replaced by an styrt radical ... ... Geological Encyclopedia

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functional group- Functional Group Functional group Structural fragment of a molecule that is characteristic of a given class of organic compounds and determines its chemical properties. Examples of functional groups: azide, hydroxyl, carbonyl, ... ... Explanatory English-Russian Dictionary of Nanotechnology. - M.

CARBOXY GROUP- (carboxyl), COOH acid group C present in (see); the number of K. g. determines the basicity of the acid ... Great Polytechnic Encyclopedia

Carboxy group, carboxyl, monovalent group characteristic of carboxylic acids. Consists of carbonyl and hydroxyl (OH) groups (hence the name: carb + oxyl) ... Big encyclopedic polytechnic dictionary

Carboxyl, functional monovalent group Carboxylic acids) and determining their acidic properties ... Great Soviet Encyclopedia

carboxyl group- carboxyl ... Dictionary of chemical synonyms I

Benzyl acetate has an ether functional group (shown in red), an acetyl group (green), and a benzyl group (orange). Functional group structural fragment of an organic ... Wikipedia

carboxyl group (carboxyl) -COOH - a functional monovalent group that is part of carboxylic acids and determines their acidic properties.

The structure of the carboxyl group

The carboxyl group combines two functional groups - carbonyl (>C=O) and hydroxyl (-OH), mutually influencing each other.

The acidic properties of carboxylic acids are due to the shift of the 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:

R-COOH = R-COO − + H+

Solubility in water and high boiling points of acids are due to the formation of intermolecular hydrogen bonds.

As the molecular weight increases, the solubility of acids in water decreases.

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An excerpt characterizing the Carboxyl group

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