Reactions And Mechanisms 2

Question 1

In terms of reactivity with nucleophiles, order the carbonyl functional groups

Answer 1

Acid chloride
Acid anhydride
Aldehyde/ketone
Ester
Amide

Question 2

Which carbonyl groups can be reduced by NaBH4

Answer 2

Acid chloride
Acid anhydride
Aldehyde/ketone

Question 3

Which reducing agent is required to reduce an ester to an alcohol?
What is the intermediate functional group?
What can not be used in reactions of LiAlH4?

Answer 3

LiAlH4
Aldehyde
Alcoholic solvents

Question 4

Which reducing agent is requires to reduce carboxylic acids to alcohols?
What are the reactions steps?

Answer 4

Borane (BH3)

RCOOH -(BH3, -3x H2)-> B(OOCR)3 (triacylborate) -(BH3)-> RCOH

Question 5

What is the product of an amide being reduced?
Which hydride is used to reduce an amide?
What is formed in one of the intermediate steps?
Why is the mechanism different to when reducing other carbonyl derivatives?

Answer 5

Amine
LiAlH4
Iminium ion
Tetrahedral intermediate does not have such a good leaving group

Question 6

Does NaBH4 reduce the carbonyl derivates? (Y/N/slow)

Answer 6

Acid chloride - Y
Acid anhydride - Y
Aldehyde/ketone - Y
Ester - slow
Amide - N
Carboxylic acid - N

Question 7

Does LiBH4 reduce the carbonyl derivatives? (Y/N/slow)

Answer 7

Acid chloride - Y
Acid anhydride - Y
Aldehyde/ketone - Y
Ester - Y
Amide - N
Carboxylic acid - N

Question 8

Does LiAlH4 reduce the carbonyl derivatives? (Y/N/slow)

Answer 8

Acid chloride - Y
Acid anhydride - Y
Aldehyde/ketone - Y
Ester - Y
Amide - Y
Carboxylic acid - slow (use BH3)

Question 9

When organometallic reagents react with acid anhydrides/halides, what is the product?
When organometallic reagents react with esters, what is the product?
What causes this difference?

Answer 9

Ketones
Alcohols
Acid anhydride/halide are more reactive than ketone product with reducing agent
With esters, the ketone intermediate is more reactive so 2x reagent needed

Question 10

How can a carboxylic acid be formed from an organometallic reagent?

Answer 10

1. CO2

2. HCl, H2O