The Crystal Structure of cis-Inositol Monohydrate—Un Objet Retrouvé

Abstract

cis-Inositol monohydrate, C₆H₁₂O₆.H₂O, crystallizes in the monoclinic space group P 2₁/n [a 9.900(8), b 9.296(8), c 17.795(15) Ǻ, β 90.5(1)°, Z 8]. The normalized structure factors E_h have an atypical statistical distribution, and attempts to solve the structure by direct methods (triplet relationships) were unsuccessful. The structure was ultimately solved by Patterson and Fourier methods, and was refined by full-matrix least squares [R_w = 0.047 for 1665 independent reflections ≥2σ(I_min)]. The cis-inositol molecules have approximately trigonal symmetry, as expected. The difficulties encountered during the structure analysis are explained by the presence of two nearly identical molecules of high symmetry in the asymmetric unit. The independent molecules are related by translational pseudosymmetry, and their orientations are such that all the C-C and C-O bonds in the structure are approximately parallel to a small number of directions.