16.1.3—Classify alcohols as primary, secondary
- Syllabus
- 9701–2028–2029
- Objective
- 16.1.3
- Level
- AS
Classify alcohols by the carbon bearing –OH and use oxidation as a supporting test
A primary alcohol has –OH on a carbon attached to one carbon, secondary to two, and tertiary to three. Acidified dichromate(VI) oxidises primary and secondary alcohols but tertiary alcohols resist mild oxidation.
On warming, orange Cr₂O₇²⁻ is reduced to green Cr³⁺ when oxidation occurs. Classification predicts the likely oxidation product, but the colour test alone does not name the alcohol.
Propan-1-ol is primary and can oxidise to propanal then propanoic acid; propan-2-ol is secondary and oxidises to propanone; tert-butanol is tertiary and shows no reaction under these conditions.
Primary/secondary/tertiary refers to the carbon attached to OH, not the number of OH groups or total carbons.
ConceptA-Level CAIE Chemistry AS