ASSAY OF 3-SUBSTITUTED PYRIDINES THROUGH FUJIWARA REACTION

Document Type : Original Article

Authors

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt

Abstract

3-Substituted pyridines of pharmaceutical interest with a carbonyl group in the 3-position have been determined by a modification of the Koenig's reaction without interferences from the 2-and 4-substituted isomers.
Nicotinic acid, nicotinamide, and nikethamide in a strongly alkaline medium were reacted with chlorbutol in absolute ethanol on a steam bath for 5 minutes. The reaction mixture was cooled in ice bath and the pH was adjusted. The chromogen was developed by the use of a solution of thiobarbituric acid, barbituric acid or benzidine dihydrochloride where a stable color was formed showing a prominent absorption peaks at 535, 580, and 525 nm respectively. The relationship between absorbance and concentration is linear in the range of 0.005 - 0.05 mg per ml for nicotinic acid, and 0.01-0.1 g per ml for nicotinamide and nikethamide. The selectivity of the method within the 3-substituted members was also investigated.