吖嗪ā qín-azine; heterocyclic compound containing nitrogen in their ring such as pyridine 吡啶[bi3 ding4] C5H5N, pyrazine 噠嗪|哒嗪[da1 qin2] C4H4N2 or pyrimidine 嘧啶[mi4 ding4] C4H4N2