Pyrimidine is an aromatic heterocyclic organic compound similar to pyridine. One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has the nitrogen atoms at positions 1 and 3 in the ring.:250 The other diazines are pyrazine (nitrogen atoms at the 1 and 4 positions) and pyridazine (nitrogen atoms at the 1 and 2 positions). In nucleic acids, three types of nucleobases are pyrimidine derivatives: cytosine (C), thymine (T), and uracil (U).
Pyrimidine ແມ່ນທາດປະສົມອົງຄະທາດທີ່ມີກິ່ນຫອມຄ້າຍຄືກັບ pyridine. ຫນຶ່ງໃນສາມ diazines (heterocyclics ຫົກກັບສອງອະຕອມໄນໂຕຣເຈນໃນວົງ), ມັນມີອະຕອມໄນໂຕຣເຈນຢູ່ໃນຕໍາແຫນ່ງ 1 ແລະ 3 ໃນວົງ .:250 diazines ອື່ນໆແມ່ນ pyrazine (ປະລໍາມະນູໄນໂຕຣເຈນຢູ່ຕໍາແຫນ່ງ 1 ແລະ 4) ແລະ pyridazine (ປະລໍາມະນູໄນໂຕຣເຈນຢູ່ຕໍາແຫນ່ງ 1 ແລະ 2). ໃນອາຊິດ nucleic, ສາມປະເພດຂອງ nucleobases ແມ່ນ derivatives pyrimidine: cytosine (C), thymine (T), ແລະ uracil (U).