18C: Organic Synthesis

Question 1

State the purpose of Grignard reagents.

Answer 1

Increasing chain length.

Question 2

Describe the preparation of Grignard reagents.

Answer 2

React bromoalkane with magnesium turnings in dry ether,
Heat under reflux.

Question 3

Reaction of Grignard reagents with carbon dioxide:
Conditions,
Product.

Answer 3

In dry ether, add dilute HCl,
Carboxylic acid.

Question 4

Describe the reaction:
Grignard reagent -> carboxylic acid

Answer 4

React with carbon dioxide in dry ether,
Add dilute HCl.

Question 5

Reactions of Grignard reagents with carbonyls:
Condition,
Products.

Answer 5

In dry ether, add dilute HCl,
Methanal -> primary alcohol
Aldehyde -> secondary alcohol
Ketone -> tertiary alcohol

Question 6

Describe the reaction:
Grignard reagent -> primary alcohol

Answer 6

React with methanal in dry ether,
Add dilute HCl.

Question 7

Describe the reaction:
Grignard reagent -> secondary alcohol

Answer 7

React with aldehyde in dry ether,
Add dilute HCl.

Question 8

Describe the reaction:
Grignard reagent -> tertiary alcohol

Answer 8

React with ketone in dry ether,
Add dilute HCl.