Functional Groups 3: Alcohols

Question 1

Why do alcohols have higher boiling points to comparative ethers?

Answer 1

Because alcohols are held together by hydrogen bonding

Question 2

How can you generate strongly basic alkoxides?

Answer 2

1) Using sodium hydride - removes protons from ROH, forms hydrogen gas, RO- and Na+
2) Using sodium metal - exothermic reaction, add sodium slowly or solution will explode

Question 3

What are alkoxides?

Answer 3

RO-
(deprotonated alcohols)

Question 4

What are alkoxides useful for?

Answer 4

Reactions with alkyl halides
Good bases in E2 reactions

Question 5

Give four methods of synthesising alcohols.

Answer 5

1) From alkyl halides
2) Hydration of alkenes
3) Reduction of aldehydes, ketones or carboxylic acid derivatives
4) Grignard reagents and carbonyls

Question 6

How would you synthesise an alcohol from an alkyl halide?

Answer 6

Reaction with hydroxide nucleophile

Question 7

How would you synthesise an alcohol from an alkene?

Answer 7

Hydration of the alkane
Add water and dilute acid catalyst

Question 8

How would you synthesise an alcohol from aldehydes, ketones, or carboxylic acid derivatives?

Answer 8

Reduction
Using NaBH4 or LiAlH4

Question 9

How would you synthesise alcohols from Grignard reagents?

Answer 9

Using R-MgBr
Forms primary alcohols with methanal
Forms secondary alcohols with other aldehydes
Forms tertiary alcohols from ketones

Question 10

Describe how tertiary alcohols can be dehydrated.

Answer 10

Using an acid with non-nucleophilic counter-ions (e.g. sulfuric acid) so that SN1 does not compete
E1 mechanism