Synthesis 4

Question 1

Name the 3 ways alcohols can be prepared

Answer 1

Hydration, nucleophilic substitution, reduction

Question 2

Describe the hydration reaction which forms an alcohol

Answer 2

Alkene + water = alcohol

Sulphuric acid catalyst

Question 3

Describe the nucleophilic reaction which forms an alcohol

Answer 3

Can be either sn1 or sn2

Usually haloalkane + OH- = alcohol

Question 4

Describe the reduction reaction which forms an alcohol

Answer 4

Aldehyde + reducing agent = primary alcohol
Ketone + reducing agent = secondary alcohol
LiAlH4 (lithium aluminium hydride) in ether
Carboxylic acid + LiAlH4 = primary alcohol

Question 5

What are the properties of alcohols

Answer 5

Hydrogen bonding present

Increase in chain length = decrease in solubility + increase in bpt

Question 6

What are the 3 reactions of alcohols

Answer 6

1. Reaction with Alkali metal to from alkoxide
2. Reaction with carboxylic acid and acid chlorides to from esters
3. Dehydration or elimination reaction to form alkene

Question 7

What happens when alcohols react with alkali metals such as Na or K

Answer 7

Alkoxide forms.

R~O~H —> oxygen takes both electrons —> R~O- (alkoxide) + H+

Question 8

How do alcohols form esters

Answer 8

By reaction with either carboxylic acids or acid chlorides in a condensation reaction
Carboxylic acids need a concentrated sulphuric acid catalyst ( or phosphoric acid)
Acid chlorides don’t need a catalyst

Question 9

How are alcohols dehydrated to from alkenes

Answer 9

1. (For simple alcohols) vapour is passed over hot aluminium oxide
2. Reaction alcohol with concentrated sulphuric or phosphoric acid. ( phosphoric preferred as it prevents charring)

Question 10

How are symmetrical ethers named

Answer 10

Di __alkyl___ ether

Question 11

How are non-symmetrical ethers named

Answer 11

\_\_\_small group (inc oxygen) prefix\_\_oxy   \_\_name alkane as normal\_\_
Eg. Methoxy ethane

Question 12

What are the properties of ethers

Answer 12

Alcohol bpt > ether bpt
Can’t H bond to itself but can H bond with water
Increase in chain length = decrease in solubility
It is volatile, flammable, and used as a solvent

Question 13

How are ethers prepared

Answer 13

Nucleophilic substitution of haloalkanes by refluxing with metal alkoxide
R~O- + R~X —> R~O~R + X-
Where alkoxide is the nucleophile