2-Phenylglycerol: crystal structure and conformational considerations pertaining to formation of its related oxetane

2-Phenylglycerol has been crystallized, structurally characterized, and its related conformations considered by ab initio calculations at the HF/6-31G* level. C9H12O3.\( \frac{1}{2} \)H2O, P21,a = 5.8786(1), b = 28.6605(7), c = 10.5553(3) A, β = 90.187 (1)° at 100(1) K, Z = 8, R = 0.0424 for 5913 unique observed reflections. The asymmetric unit contains four molecules of the title compound and two molecules of water. The structures are characterized by extensive intermolecular hydrogen bonds. The packing is dominated by a hydrophilic hydrogen bonded layer with the hydrophobic phenyl rings forming a herringbone packed intermediate layer. Computational studies suggest that an increase in energy of about 13 kcal/mol can provide for significant conformational flexibility, including the traversal of an orientation that is appropriately aligned with the reaction trajectory needed for closure to the oxetane. Progression along this reaction coordinate, however, will probably require at least another 15 kcal/mol in the gas phase in order to bring the two SN2 species into a proximity which approaches that of the oxetane's C-O bond distance.