Ch14 Alcohols

Question 1

primary alcohol

Answer 1

carbon atom bonded to OH group is only bonded to one other carbon

Question 2

secondary alcohol

Answer 2

carbon atom bonded to OH group is bonded to two carbons

Question 3

tertiary alcohol

Answer 3

carbon atom bonded to OH group is only bonded to three carbons

Question 4

boiling point of alcohols

Answer 4

very high
- induced dipole-dipole interactions
- hydrogen bonds

Question 5

miscibility with water

Answer 5

they mix together to make a single layer as hydrogen bonds are formed between alcohol and water

as mr of alcohol increases, miscibility decreases

Question 6

reactivity of alcohols

Answer 6

more reactive than alkanes because C-H and O-H bonds are polar

Question 7

combustion of alcohols

Answer 7

burn in an excess of oxygen to produce carbon dioxide and water

Question 8

oxidation of primary alcohols

Answer 8

produces an aldehyde and water

further on can produce carboxylic acid

Question 9

oxidation of secondary alcohol

Answer 9

produces a ketone and water

Question 10

oxidation of tertiary alcohol

Answer 10

can’t occur because the carbon attached to the OH must also be attached to at least one hydrogen

Question 11

common oxidising agent

Answer 11

acidified solution of potassium dichromate H+/Cr2O7^-2

Turns from bright orange to dark green when alcohol has been oxidised

Question 12

Reflux apparatus

Answer 12

ensures any volatile aldehyde condenses and flows back into flask, where excess oxidising agent ensure complete oxidation to form carboxylic acid

Question 13

distillation apparatus

Answer 13

allows aldehyde to distill off as it is formed which prevents formation of carboxylic acid by further oxidation of aldehyde

Question 14

oxidation of ethanol to ethanal

Answer 14

1. ethanol is heated with potassium dichromate and sulfuric acid in distillation apparatus
2. volatile component evaporates first
3. ethanal has lowest bp so vaporises most readily
4. condenser has cold water circulating in outer sleeve
5. when ethanal reaches condenser, it condenses and is separated from reaction mixture

Question 15

oxidation of ethanol to ethanoic acid

Answer 15

1. when reaction mixture is heated most volatile component vaporises first
2. ethanal has lowest bp so vaporises most readily
3. vertical reflux condenser has cold water circulating outer sleeve
4. when ethanal reaches condenser, it condenses and falls back into oxidising mixure
5. it is oxidised further into ethanoic acid

Question 16

elimination/dehydration of alcohols

Answer 16

when reacted with hot, concentrated sufuric acid an alchohol loses water and forms an alkene

C=C bond is formed

Question 17

alcohol substitution with halide ions

Answer 17

all alcohols react with Br- in presence of acid H+ ion

Haloalkane and water is produced by reacting alcohol with NaBr/H2SO4

Question 18

Ester formation

Answer 18

All alcohols react with carboxylic acid to form esters and water

concentrated H2SO4 is needed