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3.2.9—Oxidation of organic functional groups

Syllabus
First assessment 2025
Objective
3.2.9
Level
SL

Oxidation of Alcohols

A primary alcohol oxidizes to an aldehyde and then a carboxylic acid; a secondary alcohol oxidizes to a ketone. Reflux supports further oxidation to the acid, while distillation can remove an aldehyde.

R–CH2OH becomes R–CHO; the aldehyde retains one H on the carbonyl carbon; H2O is shown as in the approved source.
R–CHO becomes R–COOH; the same carbonyl carbon and R group are retained; no unsupported water product is added.
R–CH(OH)–R′ becomes R–C(=O)–R′; both R groups and the functional carbon are retained; H2O is shown as in the approved source.
the structure is (CH3)3C–OH; the carbon bearing OH has no H; the non-reaction claim is explicitly limited to the stated reflux/distillation oxidizing conditions.

In a primary-alcohol experiment, distil the aldehyde as it forms to limit further oxidation; heat under reflux when the carboxylic acid is required. Tertiary alcohols lack the required hydrogen on the carbon bearing –OH and are not oxidized in the same way.

Choosing Alcohol-Oxidation Products

[ 2 ]

Deduce the organic products when butan-1-ol and butan-2-ol are separately heated under reflux with acidified potassium dichromate(VI).

Butan-1-ol:
Butan-2-ol:

Electron Transfer Reactions Summary

Retrieve the route: assign oxidation states, balance half-equations, predict displacement, label cells, trace electrons and ions, follow organic redox pathways, calculate potentials and choose electrolysis products.

Check electron loss/gain, anode/cathode versus polarity, spontaneous sign, salt-bridge direction, ions present, organic functional-group direction and object-cathode placement.