Reduction of Carbonyls

Question 1

What are aldehydes reduced to?

Answer 1

Primary Alcohols

Question 2

What are ketones reduced to

Answer 2

Secondary alcohols

Question 3

What is the most common reducing agent?

Answer 3

NaBH4
Tetrahydridoborate
Sodium Borohydride

Question 4

How does NaBH4 act as a reducing agent reducing aldehydes and ketones?

Answer 4

• Nucleophilic addition
• In aqueous solutions, NaBH4 generates nucleophile :H-
• Hydride ion reduces carbonyl group in aldehyde or ketone, but not strong enough for C=C bonds (attracted to the C in C=O bond, but repelled by high electron density of C=C bond

Question 5

Difference between reduction of a carboxylic acid and aldehyde?

Answer 5

• Although both reduce to primary aclcohols
• COOH reduces to primary alcohol + water
• COH reduces to just primary alcohol