Crystal structures of 3-methyl-2(1H)-quinoxalinone and three substituted derivatives

摘要

3-Methyl-2(1H)-quinoxalinone and three derivatives (3,7-dimethyl-2(1H)- quinoxalinone, 3-methyl-6,7-dichloro-2(1H)-quinoxalinone and 3-methyl-7-nitro-2(1H)-quinoxalinone) have been synthesised and analysed by ~1H NMR and IR spectral spectroscopies. The crystal structures have been determined at room temperature from X-ray single crystal diffraction data for three of them and from powder diffraction data for the nitro derivative. 3-Methyl-2(1H)-quinoxalinone crystallises in the P2_1/c monoclinic system, 3,7-dimethyl-2(1H)-quinoxalinone in the Pbca orthorhombic system and the two others compounds in the P1? triclinic system. For the nitro derivative, C-H.N short contacts are established between the carbon of the methyl and the double bounded nitrogen of the ring. For the three other compounds N-H.O hydrogen bonds involve the atoms of the heterocyclic ring.