The Acidity of Norfloxacin

Abstract

A ¹H and ¹³C n.m.r. investigation of the fluoroquinolone carboxylic acid Norfloxacin (1) in D₂O has allowed three pK_a values to be determined, which correspond to carboxylic acid oxygen (pK_a^D 0.6), pyridone nitrogen (pK_a^D 6.9) and 'external' piperazine nitrogen (pK_a^D 9.25) ionization.