4-Chloroquinoline is an important raw material and intermediate used in organic synthesis, pharmaceuticals, agrochemicals and dyestuffs.
Possible impurities include the 2-isomer. It is best purified by converting to the picrate (m 212-213o dec) in EtOH and recrystallising it from EtOH (where the picrate of the 2-chloroquinoline remains in solution) or EtOAc . The picrate is decomposed with 5% aqueous NaOH, extracted in CHCl3, washed with H2O, dried (MgSO4), evaporated and distilled in a vacuum. It can be steam distilled from slightly alkaline aqueous solutions, the aqueous distillate is extracted with Et2O, evaporated and distilled. The distillate solidifies on cooling. [Bobránski Chem Ber 71 578 1938, Beilstein 20/7 V 314.]
