5-chloropyrazinamide , its cas register number is 21279-64-1. It also can be called 2-Carboxamido-5-chloropyrazine ; 5-Chloro-2-pyrazinecarboxamide ; 5-chloro-pyrazinamide ; Pyrazinecarboxamide, 5-chloro- ; 5-Chloro-PZA .