β-picoline

3-Methylpyridine or 3-picoline, is an organic compound with formula 3-CH3C5H4N. It is one of three positional isomers of methylpyridine, whose structures vary according to where the methyl group is attached around the pyridine ring. This colorless liquid is a precursor to pyridine derivatives that have applications in the pharmaceutical and agricultural industries. Like pyridine, 3-methylpyridine is a colorless liquid with a strong odor and is classified as a weak base.

==Synthesis== 3-Methylpyridine is produced industrially by the reaction of acrolein, with ammonia. These ingredients are combined as gases which flows over an oxide-based heterogeneous catalyst. The reaction is multistep, culminating in cyclisation. 2 CH2CHCHO + NH3 → CH3C5H4N + 2H2O This process also affords substantial amounts of pyridine, which arises by demethylation of the 3-methylpyridine. A route that gives better control of the product starts with acrolein, propionaldehyde, and ammonia: CH2CHCHO + CH3CH2CHO + NH3 → 3-CH3C5H4N + 2 H2O + H2 It may also be obtained as a co-product of pyridine synthesis from acetaldehyde, formaldehyde, and ammonia via Chichibabin pyridine synthesis. Approximately 9,000,000 kilograms were produced worldwide in 1989. It has also been prepared by dehydrogenation of 3-methylpiperidine, derived from hydrogenation of 2-Methylglutaronitrile.