CARBOXYLIC ACID

CARBOXYLIC ACID
Introduction:
Organic compounds containing (–C(O)–OH) as a functional group are called carboxylic acids. The –C (O)-OH group which itself is made up of a carbonyl group (>C=O) and a hydroxyl group (-OH) is called a carboxyl group (carb from carbonyl and oxyl from hydroxyl group). Carboxylic acid may be an aliphatic or an aromatic depending upon whether –C–OH is attached to an alkyl group ( or a hydrogen atom) or an aryl group.
Their general formulas are;
ALIPHATIC CARBOXYLIC ACID:
R–C (O)–OH where R=H or an alkyl group.
Example:

AROMATIC CARBOXYLIC ACID:
Ar–C–OH where Ar is a phenyl or aryl group.
Examples:

CLASSIFICATION:
Carboxylic acids are further classified as ; Mono, di , tri, or poly carboxylic acids as they contain one, two, three or many carboxyl groups respectively in their molecules.

General method of preparation:

1. From primary alcohols
Primary alcohols and aldehydes are readily oxidized to corresponding carboxylic acids by oxidizing agents such as potassium dichromate in an acidic medium.
R–CH2–OH + [O] R–CHO+ [O] ­­­­­­­­­­ RCOOH
CH3–CH2–OH + [O] CH3–CHO + [O] CH3COOH

2. From aldehydes:
Aldehydes are easily oxidized to corresponding carboxylic acids even by mild oxidizing agents such as Tollen’s Reagent ( Ammonia cal silver nitrates).
CH3–CHO+ [O] CH3COOH

3. From alkyl nitriles:
Compounds having a cyanide ( ­–CN) group are called nitriles. Hydrolysis of an alkyl nitrile on boiling with mineral acid or alkalis yield corresponding carboxylic acid .
R–CN +H2O RCOOH +NH3
CH3–CN + 2H2O+HCL CH3COOH + NH4CL

4. BY OXIDATIVE CLEAVAGE OF ALKENES:
Alkenes when heated with alkaline KMNO4 are cleaved at double bond to form carboxylic acids.
R–CH=CH–R +4[O] 2RCOOH
H3C–CH=CH–CH3 + [O] 2CH3COOH
REACTIONS OF