As we noted in Chapter 14 “Organic Compounds of Oxygen”, the oxidation of aldehydes or primary alcohols forms carboxylic acids:

In the presence of an oxidizing agent, ethanol is oxidized to acetaldehyde, which is then oxidized to acetic acid.

This process also occurs in the liver, where enzymes catalyze the oxidation of ethanol to acetic acid.

CH3CH2OH →oxidizing agentalcohol dehydrogenase CH3CHO →oxidizing agentalcohol dehydrogenase CH3COOH

Acetic acid can be further oxidized to carbon dioxide and water.

Concept Review Exercises

1. Caproic acid (hexanoic acid) can be prepared in an oxidation reaction from

   1. what alcohol?
   2. what aldehyde?

2. Give the structures of the aldehyde and the carboxylic acid formed by the oxidation of isobutyl alcohol [(CH₃)₂CHCH₂OH].

Show Answer

1. a. CH₃CH₂CH₂CH₂CH₂CH₂OH

b. CH₃CH₂CH₂CH₂CH₂CHO

2. 

Key Takeaway

• Whether in the laboratory or in the body, the oxidation of aldehydes or primary alcohols forms carboxylic acids.