Gabapentin [or 1-(aminomethyl)cyclohexaneacetic acid], C(9)H(17)NO(2), exists as a zwitterion [1-(ammoniomethyl)cyclohexaneacetate] in the solid state. The crystal structures and bonding networks of two new monoclinic polymorphs (beta-gabapentin and gamma-gabapentin) are studied and compared with a previously reported gabapentin polymorph [alpha-gabapentin: Ibers (2001). Acta Cryst. C57, 641-643]. All three polymorphs have extensive networks of hydrogen bonds between the NH(3)(+) and COO(-) groups of neighbouring molecules. In beta-gabapentin, there is an additional weak intramolecular hydrogen bond.
Acta Cryst. (2007). A63, s69 phase of CH 2 I 2 [5]. In the polar Fmm2-symmetric phase the dipole moments of all molecules are parallel. A group of isostructural crystals has been identified for a series of 1,2-dihalotetrafluoroethanes X(CF 2) 2 Y (X = Br, I; Y = Br, I). Despite their isostructurality the molecules behave differently. The BrCF 2 CF 2 Br structure is completely ordered, in ICF 2 CF 2 I the-CF 2-CF 2-moiety rotate about I···I molecular axis, but it orders at pressure higher than 1 GPa, and in the BrCF 2 CF 2 I structure the Br and I atoms are disordered. The formation of isostructural crystals by these compounds and different types of molecular disorder can be rationalized by the similar patterns of intermolecular interactions. In the crystal of dichloroacetic acid (P2 1 /n), molecules are connected by chlorine•••chlorine interactions into infinite zigzag chains While the structures of the series of halogenated methanes and ethanes are clearly governed by halogen•••halogen interactions, we encountered also structures where this type of interactions was absent. For example, in the crystal structure of chlorotrimethylsilane Si(CH 3) 3 Cl (Pmn2 1), no such intermolecular contacts shorter than 5Å have been observed [6]. MS27 O4 The influence of environment on structure: Polymorphs of γ-aminobutyric acid (GABA) and gabapentin
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