Alcohols

Question 1

Burn with oxygen

Answer 1

Type of reaction: combustion
Products: CO2 and H2O, C/CO and H2O
Observation: clean blue/pale yellow flame

Question 2

With PCl5 (all alcohols)

Answer 2

Type of reaction: chlorination/nucleophilic substitution
Condition: mix at room temperature
Change in functional group: alcohol –> chloroalkane
Observation: HCl (acidic steamy fume) which turns damp blue litmus paper red

Question 3

With conc. HCl (only tertiary alcohol)

Answer 3

Type of reaction: chlorination/nucleophilic substitution
Condition: heat under reflux
Change in functional group: alcohol –> chloroalkane

Question 4

With KBr and 50% sulfuric acid

Answer 4

Type of reaction: bromination/nucleophilic substitution
Condition: heat under reflux
Change in functional group: alcohol –> bromoalkane

Question 5

With damp red phosphorus and iodine

Answer 5

Type of reaction: iodination/nucleophilic substitution
Condition: warm
Change in functional group: alcohol –> iodoalkane

Question 6

With acidified potassium dichromate (primary)

Answer 6

Type of reaction: oxidation
Condition: distillation
Change in functional group: alcohol –> aldehyde

Question 7

With excess acidified potassium dichromate (primary)

Answer 7

Type of reaction: oxidation
Condition: heat under reflux
Change in functional group: alcohol –> carboxylic acid

Question 8

With acidified potassium dichromate (secondary)

Answer 8

Type of reaction: oxidation
Condition: heat under reflux
Change in functional group: alcohol –> ketone

Question 9

With hot aluminium oxide or concentrated phosphoric acid

Answer 9

Type of reaction: elimination
Condition: pass over hot aluminium oxide or warm with concentrated phosphoric acid
Change in functional group: alcohol –> alkene

Question 10

Test for alcohol with PCl5

Answer 10

Purpose: to test for -OH group
Observation: steamy fumes of HCl
Further test: test with damp blue litmus paper - remains blue for alcohol and turns red for carboxylic acid

Question 11

Test for alcohol with Benedict’s/Fehling’s solution

Answer 11

Purpose: to distinguish primary and secondary alcohol
Condition: warm with acidified potassium dichromate and distil off the product, add Fehling’s or Benedict’s solution and warm in water bath
Observation: brick red precipitate for primary alcohol (aldehyde), no precipitate for secondary alcohol (ketone)