`Topic 6 Alcohols

Question 1

Chlorination of alcohol
Primary, Secondary, Tertiary

Answer 1

Primary + Secondary:
Phosphorus (V) Chloride at room temp. Produces hydrogen chloride and phosphorus oxychloride.
Tertiary:
Shake with concentrated hydrochloric acid at room temp.

Question 2

Classification of alcohols

Answer 2

By number of alkyl groups attached.
1 = Primary
2 = Secondary
3 = Tertiary

Question 3

Bromination of alcohol.

Answer 3

In a mixture of 50% concentrated sulphuric acid and potassium bromide. React to form HBr which then reacts with alcohol
Warmed with the alcohol

Question 4

Iodination of alcohol

Answer 4

A mixture of red phosphorus and iodine. React to form phosphorus (III) iodide. This is heated under reflux with alcohol.

Question 5

Dehydration of alcohol to alkenes (elimination)

Answer 5

Heating alcohol with conc phosphoric acid. Water is produced, can be multiple products as the H is removed from a adjacent carbon atom.

Question 6

Products of oxidation of alcohols

Answer 6

Ketone: Secondary alcohol is oxidised. RCOR.
Aldehydes: Primary alcohol is oxidised to form an aldehyde. RCHO.
Carboxylic acid: A aldehyde is easily further oxidised to form a carboxylic acid. RCOOH.

Question 7

What oxidation agents are used for alcohols

Answer 7

A mixture of Pottasium dichromate (VI) in dilute sulfuric acid. This causes a color change from orange to green.

Question 8

Practical technique for complete oxidation

Answer 8

Heating under reflux. Products stay in the reaction mixture as when they boil off they can cool and condense in the vertical condenser.

Question 9

Practical technique for incomplete oxidation.

Answer 9

Formation of aldehyde by distillation with addition.
Heating only the oxidation agent with the alcohol slowly added from above. Aldehyde has a low boiling temperature so will immediately distill off.