Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Forty nine three-dimensional crystal structures of a benzylphenyl ether fragment retrieved from the Cambridge Structural Database were confronted with computed conformational maps of the fragment. Due to the symmetry the number of analyzed fragments rose to 98. When an endocyclic torsion angle of a phenyl ring deviates from 0° the adjacent torsion angle is deformed in opposite direction compensating thus the deviation from planarity. The shape of the fragment is mainly controlled by torsion angles τ₁ = C-C-O-CH₂, τ₂ = C-O-CH₂-C, and τ₃ = O-CH₂-C-C. The attachment of both phenyl rings to the -CH₂-O- moiety is not symmetrical and the deformation depends on the value of the τ₃ angle. In the crystal, the fragment prefers conformation with τ₁ around 0°, τ₂ around 180° and with broad bimodal distribution of τ₃ around 0° and ±90° despite the fact that energetically equivalent regions exist in the potential energy maps for τ₂ values near 60° and 300° and that many crystal structures with τ₃ around 0° lie in higher energetical regions than those with τ₃ around 90°. Thus a significant difference between the crystal and simulated gas phase conformations was observed supporting the hypothesis that crystals prefer flatter and more storable molecular conformations.