52E - Organic Chemistry (Mcmurry)

Question

3-Methyl-2-hexenoic acid (mixture of E and Z isomers) has been identified as the substance responsible for the odour of human sweat. Synthesize the compound from starting materials having five or fewer carbons

Step-by-Step Solution

Answer

Starting from 2-pentanone having five carbons 3 methyl-2-hexenoic acids can be synthesized by the steps

Step 1: Definition of compounds

Any substance composed of identical molecules consisting of atoms of two or more chemical elements is defined as a chemical compound.

Step 2: Explanations

Treating 2-pentanone with allyl magnesium bromide and hydrolyzing produces an unsaturated tertiary alcohol, 3-methylhhex-1-ene-3-ol. The double bond gets hydrated during hydroboration using BH₃, THF ad oxidation using H₂O₂, OH- to yield the diol, 3-methylhexan-1,3-diol. The primary alcoholic group in 3-methylhexan-1,3-diol is oxidized by CrO₃ in aqueous acids to give 3-hydoxyacid,3-hydroxy-3-methylhexanoic acid. In presence of aqueous acids the hydroxyacid dehydrates and produces 3-methyl-2-hexenoic acid (both E and Z isomers).

Starting from 2-pentanone having five carbons 3 methyl-2-hexenoic acid can be synthesized by the steps.