2.10.1d: demonstrate an understanding of, and practise, the preparation of an organic liquid (reflux and distillation), eg oxidation of alcohols

OXIDATION OF PRIMARY ALCOHOLS

A primary alcohol can be oxidised to an aldehyde and then a carboxylic acid

• eg. INSERT DIAGRAM OF DISPLAYED FORMULAE HERE

Procedure:

1. a primary alcohol is mixed with an excess of acidified potassium dichromate (ensures that there is enough oxidising agent for the complete oxidation of the alcohol)
2. the mixture is heated under reflux to allow the aldehyde to evaporate, condense, and drip back into the mixture to continue oxidation (the colour changes from orange to green due to the chromium ion changing oxidation state from +6 in the dichromate ion to +3 in the final mixture)

• partial oxidation = RCH2OH + [O] → RCHO + H2O
• forms an aldehyde with a carbonyl group (C=O) and the suffix -al
• complete oxidation = 3RCH2OH + 2Cr2O72- + 16H+ → 3RCOOH + 4Cr3+ + 11H2O
• forms a carboxylic acid with a carboxyl group (COOH)

OXIDATION OF SECONDARY ALCOHOLS

A secondary alcohol can be oxidised to a ketone

• carbonyl group and the suffix -one

R1CH(OH)R2 + [O] → R1COR2 + H2O

OXIDATION OF TERTIARY ALCOHOLS

Tertiary alcohols cannot be oxidised under normal conditions due to the lack of hydrogen atoms attached to a carbon + functional group

REFLUX APPARATUS

Continuous evaporation and condensation

DISTILLATION APPARATUS