Purification of 2-Methylpyridine

Biddiscombe and Handley steam distd a boiling soln of the base in 1.2 equivalents of 20% H2SO4 until about 10% of the base had been carried over, along with non-basic impurities. Excess aqueous NaOH was then added to the residue, the free base was separated, dried with solid NaOH and fractionally distd.

2-Methylpyridine (CAS NO. 109-06- can also be dried with BaO, CaO, CaH2, LiAlH4, sodium or Linde type 5A molecular sieves. An alternative purification is via the ZnCl2 adduct, which is formed by adding 2-methylpyridine (90mL) to a soln of anhydrous ZnCl2 (168g) and 42mL conc HCl in absolute EtOH (200mL). Crystals of the complex are filtered off, recrystd twice from absolute EtOH (to give m 118.5-119.5 °C), and the free base is liberated by addition of excess aqueous NaOH. It is steam distd, and solid NaOH added to the distillate to form two layers, the upper one of which is then dried with KOH pellets, stored for several days with BaO and fractionally distd. Instead of ZnCl2, HgCl2 (430g in 2.4L of hot water) can be used. The complex, which separates on cooling, can be dried at 1100 and recrystd from 1% HCl (tom 156-157 °C).