Pyrazine-2,3-dicarboxylic acid

Abstract

The title compound, C6H4N2O4, is a new unsolvated form of pyrazine-2,3-dicarboxylic acid. The asymmetric unit contains two independent molecules with different geometry. The planes of the carboxylic groups make dihedral angles with the planar pyrazine rings of 22.7 (2) and 50.0 (2)° in one molecule, and 9.7 (2) and 79.1 (2)° in the other. The molecules form layers in which hydrogen bonds occur, with O⋯O distances ranging from 2.728 (2) to 2.773 (2) A. The shortest distance between two adjacent layers is 3.5 A, indicating van der Waals interactions. © 2004 International Union of Crystallography Printed in Great Britain - all rights reserved.