Oxidation Of Alcohols: Preperations Of Benzoic Acid

Question 1

What are the objectives of this topic?

Answer 1

1) to prepare benzoic acid by oxidation of benzyl alcohol

2) purify the product by recrystalization

Question 2

What is meant by oxidation and reduction and what are the products of different oxidative rxns?

Answer 2

Oxidation is the loss of hydrogen or gain of oxygen, while reduction is the gain of hydrogen or the loss of oxygen:

Primary alcohols: oxidized to aldehydes then to carboxylic acids

Secondary alcohols: oxidized to ketones

Tertiary alcohols: not oxidize let use to the lack of hydrogen atom

Oxidation of branched benzene rings gives the corresponding carboxylic acid

Question 3

How is benzoic acid synthesized?

Answer 3

Benzoic Acid (Benzene carboxylic acid) can be prepared by oxidation of any branched benzene ring (not tertiary), Benzene is unaffected by strong oxidizing agent. But primary and secondary alkyl groups (but not tertiary groups) directly attached to a benzene ring are oxidized by KMnO4 (in basic media) and K2CrO4 (in acidic media) to give benzoic acid

Starting materials containing an alkyl substituted benzene can be oxidized with potassium permanganate, chromium trioxide, nitric acid or oxygen (in the presence of a catalyst) to give benzoic acid.