Architecture of the hydrophobic and hydrophilic layers as found from crystal structure analysis of N-benzyl-N,N-dimethylalkylammonium bromides

The molecular and crystal structures of N-benzyl-N,N-dimethylalkylammonium bromides monohydrates with chain length n=8-10 have been determined. The crystals are isostructural with the N-benzyl-N,N-dimethyldodecylammonium bromide monohydrate. The structures consist of alternated hydrophobic and hydrophilic layers perpendicular to [001]. The attraction between N+ of the cation head-groups and Br− anions is achieved through weak CH⋯Br interactions. The water molecules incorporated into ionic layers are donors for two OH⋯Br hydrogen bonds and serve as the acceptors in two weak interactions of CH⋯O type. The methylene chains, with the slightly curved general shape, have the extended all-trans conformation. The mutual packing of the chains in the hydrophobic layers is governed by weak CH⋯π interactions.