Chapter 8: 8.3 Preparation of Alcohols

Question 1

What reaction can be used to prepare alcohols?

Answer 1

Substitution reactions of alkyl halides with water/hydroxide

Question 2

How can primary or secondary alkyl halides become alcohols?

Answer 2

Undergo SN2 substitution reactions with an alkoxide/hydroxide nucleophile in aprotic solvents
* REMEMBER: E2 reaction may compete

Question 3

How can secondary or tertiary alkyl halides become alcohols?

Answer 3

Undergo SN1 substitution reactions in protic solvents (H2O, MeOH, EtOH)
* REMEMBER: Carbocations may rearrange

Question 4

Compare:

Aldehydes vs. Ketones

Answer 4

Aldehydes:
* Suffix -al
* 1 R group, 1 hydrogen

Ketones:
* Suffix -one
* 2 R groups

Both:
* Experience weak dipole-dipole interactions
* Mildly acidic at the alpha-carbon (pKa ~ 20)

Question 5

True or False:

Aldehydes and Ketones are reactive in two places

Answer 5

True

Question 6

Where are aldehydes/ketones reactive?

Answer 6

1. Electrophilic at the carbon of the carbonyl
2. Nucleophilic when deprotonated at the alpha-carbon

Question 7

True or False:

Aldehyde and ketone are more electrophilic than the carboxylic acid derivatives

Answer 7

True

Question 8

More electrophilic means…

Answer 8

More reactive

Question 9

True or False:

Ketone is more reactive than aldehyde

Answer 9

False, aldehyde is more reactive than ketone due to sterics

Question 10

General Mechanism at the Carbonyl:

Why is the carbon at the base of the carbonyl electrophilic?

Answer 10

Bond dipole between the carbon and the oxygen atom

Question 11

Explain:

The steps of the General Mechanism at the Carbonyl

Answer 11

1. The nucleophile attacks the carbon atom
2. The tetrahedral intermediate is formed
3. The final product is protonated upon work-up

Question 13

What does “work-up” mean?

Answer 13

The reaction is treated with something to balance charges when it is done

Question 14

How are charges balanced (“work-up”) in a nucleophilic addition reaction?

Answer 14

1. If reaction has negative charges, acid is added
2. If reaction has positive charges, base is added

Question 15

In the General Mechanism at the Carbonyl:

What happens if the tetrahedral intermediate does not have a good leaving group?

Answer 15

It “gets stuck” until the work-up step

Question 16

True or False:

Sodium borohydride is a weak reducing agent

Answer 16

True

Question 17

State:

The formula of sodium borohydride

Answer 17

NaBH4

Question 18

Sodium borohydride is a weak reducing agent, this means that it only reacts with…

Answer 18

Aldehydes and Ketones

Question 19

What does a reduction reaction lead to?

Answer 19

Less bonds to an oxygen atoms and more bonds to hydrogen atoms

Question 20

What results from the reduction of:
1. An aldehyde?
2. A keton?

Answer 20

1. A primary alcohol
2. A secondary alcohol