The crystal of exo-1, 4-epoxy-cyclohexyl-2, 3-liearboxylic acid in monohydrate (C8H10O5.H2O) belongs to monoclinic system, space group P21/n. There are four molecules in an unit cell with parameters α=5.594(3)A, b=11.178(7)A, c=14.675(11)A, β=91.46(5). The three dimensional intensity data were obtained with a Syntex R3 four-circle diffractometer, and the number of the independent diffractions amounted to 1626. The structure was solved by direct method and refined by block-diagonal least-squares method. The final R is 0.072. In the crystal, there are O--H. . .O hydrogen bonds between molesules, to form layer hydrogen bond system. We use the CNDO/2 programmes written by ourselves on Nova-Eclipse computer to compute the electron energy, molecular total energy, dipole moment, the charge density and net charge of each atom of the molecule C8H10O5.

Key words: CRYSTAL STRUCTURE DETERMINATION, DICARBOXYLIC ACID, MATRICES, CYCLOHEXYL GROUP, LEAST SQUARE METHODS, BRIDGE COMPOUNDS