13. Reactions of the carbonyl functional group

Question 1

What is the electronic nature of the carbonyl group?

Answer 1

The double bond is comprised of sigma and pi bonds

- Mostly it is the pi bond that is broken when the nucleophile attacks it

Question 2

What is oxidation?

Answer 2

The loss of hydrogen or the addition of oxygen to an organic molecule

Question 3

What is reduction?

Answer 3

The loss of oxygen or the addition of hydrogen to an organic molecule

Question 4

What does the oxidation of primary alcohols involve?

Answer 4

Primary alcohols can be oxidised to aldehydes or carboxylic acids
-Conversion to the aldehyde uses milder conditions (lower temp)

Question 5

How does oxidation directly to the acid occurs?

Answer 5

Potassium permanganate is a powerful oxidant and cannot be used to form aldehydes from alcohols - the acid is always formed

Question 6

What does the oxidation of secondary alcohols involve?

Answer 6

Secondary alcohols can be oxidised to ketones

Question 7

What happens in nucleophilic addition reactions with aldehydes and ketones?

Answer 7

Attack of a nucleophile leads to the loss of the pi bond and formation of a new sigma bond
- Hybridisation at carbon changes from sp2 to sp3

Question 8

What happens in the nucleophilic addition of a hydride?

Answer 8

• Addition of hydride leads to an alkoxide
• Protonation of the alkoxide affords an alcohol
• This process is a reduction

Question 9

What are some common reducing agents?

Answer 9

LiAlH4, lithium aluminium hydride

NaBH4, Sodium borohydride

Question 10

What happens in the reduction of carboxylic acids?

Answer 10

LiAlH4 will reduce carboxylic acids directly to alcohols

- It is not possible to stop at the intermediate aldehyde as these are more reactive than the acid