Sunday, January 20, 2008

AIEEE Chemistry Unit 23E Carboxylic Acids

Carboxylic acids are the compound containing carboxyl group in their molecules.

-c with a double bond with oxygen and single bond with OH

The carboxyl group is made up of carbonyl C with double bond with oxygen, and hydroxyl group OH. The carboxyl is formed carbo + oxyl.

These acides can be aliphatic or aromatic.

aliphatic acids

Formic acid HCOOH
Acetic acid CH-3COOH
Isobutyric acid (Branched)

aromatic acids

Bezoic acid : H in benzene substituted by COOH

m-Nitrobenzoic acid: One more H substituted by NO-2

o-Toluic acid (o refers to ortho) Benzoic acid with one more H substituted by CH-3

Dicarboxyic acids

Oxalic acid
Malonic acid
Succinic acid
Phthalic acid - It is an aromatic carboxylic acid

In the nomenclature, in common system, position of the sustituents is indicated by the greek letter alpha, beta, gamma and delta.

the carbon atom adjacent ot the carboxyl carbon is assigned the letter α, thenext carbon on chain is beta an so on.

According to the IUPAC system, the name of the acid is derived from the corresponding alkane by replacing the terminal 'e' with the '-oic' and adding the word acid.

The position of the substituents is indicated by the following rules:
1. The longest chain containing the carboxylic group (-COOH) is selected.
2. The carbon chain is numbered form the carboxylic acid group. The carbon of carboxyl group is always given number one.
3. The position of the substituents is indicated by the number.

Methods of Preparation of Monocarboxylic Acids:
1. From oxidation of primary alcohols
2. By oxidation of aldehydes and ketones.
3. By Hydrolysis of cyanides (or Nitriles)
4. By Grignard reaction
5. By hydrolysis of esters
6. By carboxylation of alkenes
7. From trihalogen derivatives of hydrocarbons
8. Aromatic acids from alkyl benzenes

Physical properties


Reactions of carboxylic Acids

covered under the following heads

A. reactions due to hydrogen atom of carboxyl group
B. reactions due to OH carboxyl group
C. reactions due to carboxyl group
D. reactions due to alkyl group and benzene ring.

A. Reactions due to hydrogen atom of carboxyl group

1. Acidic Properties

B. Reactions due to OH carboxyl group
1. Formation of an acid anhydride
2. Formation of Esters
3. Formation of amides
4. Formation of acid chlorides

C. Reactions due to carboxyl group
1. Decarboxylation
2. Reduction
3. Action of bromine on silver salt of the acid
D. reactions due to alkyl group and benzene ring.
1. Halogenation
2. Ring substitution in aromatic acids

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