26.1 - Carbonyl Compounds

Question 1

What is a carbonyl functional group and what are 2 carbonyl compounds?

Answer 1

• C=O

Aldehydes - carbonyl at end of chain

Ketones - carbonyl joined to 2 carbon atoms at the C of C=O

Question 2

How doe aldehydes oxidise?

Answer 2

They oxidise to cabroxylic acids under reflux w/ K₂Cr₂O₇/H₂SO₄

(Ketones do not oxidise - good way to distinguish between aldehydes and ketones)

Question 3

What occurs during carbonyl nucleophilic addition?

Answer 3

• C=C non-polar, C=O is polar
• C=O polarity attracts nucleophiles to atack
• Nucleophilic addition as opposed to electropgilic addition of C=C

Question 4

How are aldehydes and ketones reduced?

Answer 4

CARBONYL COMPOUNDS + NaBH₄

• Sodium borohydride is a reducing agent

ALDEHYDES REDUCTION

Aldehyde → 1^o alcohol

CH₃CH₂CH₂COH + 2[H] → CH₃CH₂CH₂CH₂OH

[H] - reducing agent

KETONE REDUCTION

Ketone → 2^o alcohol

CH₃COCH₃ + 2[H] → CH₃CH(OH)CH₃

Question 5

What happens when you add HCN to a carbonyl compound?

Answer 5

• HCN adds across C=O of aldehydes & ketones
• HCN: colourless, poisonous liquid
• To make HCN
  
  • ​2NaCN + H₂SO₄ → 2HCN + Na₂SO₄
• Useful reaction to increase carbon chain length

Question 6

Describe and explain the carbonyl reduction mechanism.

Answer 6

Nucleophilic addition

1. Hydrogen lone pair on hydride ion attracted to C (partially positive).
2. π-bond breaks b heterolytic fission
3. Dative covalent bond forms
4. Intermediate (-ve charge) is protonated

SEE TEXTBOOK

Question 7

Draw and explain the NACN/H⁺ mechanism

Answer 7

SEE TEXTBOOK