Formic Acid → Valeric acid, 2,2,4-trimethyl-

2,4-Dimethyl-3-pentanol (29 g, 0.25 mole), dissolved in formic acid (98%, 46 g, 1 mole), was added dropwise over one hour to a rapidly-stirred, ice-cooled mixture of formic acid (98%, 3 ml) and concentrated sulfuric acid (270 ml). During the addition the reaction mixture foamed vigorously and was stirred for a further one hour at 10°-20° C. The mixture was poured on to ice (1 kg) and the resulting solution extracted with hexanes (3×200 ml). The combined organic phases were extracted with 2N potassium hydroxide (2×200 ml) plus ice (50 g) and the aqueous extracts washed with hexanes (100 ml). The aqueous phase was then acidified (pH 2) and the product extracted into hexanes (3×200 ml). After washing with saturated sodium chloride and drying (MgSO4), the solution was evaporated under reduced pressure and the residue distilled to give 2,2,4-trimethylpentanoic acid (36 g).