Sunday, July 27, 2008

Carboxylic Acid - July-December Revision

JEE syllabus

Carboxylic acids:
Preparation, properties
Characteristic reactions
formation of esters,
acid chlorides and amides,
ester hydrolysis;
I. Carboxylic acids are the compound containing carboxyl group in their molecules.

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



II. These acids 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. It is the simplest aromatic carboxylic acid.

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

III. Methods of Preparation of Monocarboxylic Acids:

1. From oxidation of primary alcohols

2. By oxidation of aldehydes and ketones.

3. From hydrolysis of nitriles and cyanides
the nitriles are hydrolysed in dilute acqueous acidic or alkaline medium.

4. From Grignard reagents
The reaction is carried out by bubbling CO2 through the etheral solution of suitable Grignard reagent.

5. By hydrolysis of esters
Hydrolysis of esters with mineral acids or alkalines gives carboxylic acids

6. Carboxylation of alkenes
Heating alkenes with CO and steam under pressure with phospoiric acid at 673 K. This reaction is called Koch reaction.

7. From trihalogen derivatives of hydrocarbons
Hydroysis of 1,1,1,-trihalogen derivatives of alkanes with acqueous KOH.

8. Preparation of aromatic acids from alkyl benzenes
the alkyl side chain of benzene ring can be easily oxidized to carboxylic group with alkalines KMnO4, chromic anhydride or conc. HNO3.

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