Crystal structures of bis(quaternaryammonium bromide) surfactants, ethanediyl-1,2-bis(butyldimethylammonium bromide) dihydrate and propanediyl-1,3-bis(butyldimethylammonium bromide)

Abstract

The crystal structures of two bis(quaternaryammonium bromide) surfactants, CH 3(CH 2) 3N +(CH 3) 2–(CH 2) n s –N +(CH 3) 2(CH 2) 3CH 3·2Br − ( n s=2, 3), have been determined by single-crystal X-ray diffraction. The surfactant n s=2 (dihydrate, C 14N 34N 2Br 2·2H 2O, M r =426.28) crystallizes in the monoclinic space group P2 1/ n with unit cell dimensions a=8.1627(5), b=8.1627(5), c=12.5964(8) Å and β=99.203(5)°. The crystal of surfactant n s=3 (C 15H 36N 2Br 2, M r =404.27) has an orthorhombic space group Pbcn with unit cell dimensions a=13.947(2), b=16.924(1) and c=17.145(2) Å. The two n-butyl chains for n s=2 are in the trans configuration with respect to the N–(CH 2) n s –N skeleton, while those for n s=3 are in the cis configuration. The (CH 2) 3 segments of the two n-butyl chains are in the extended form, while the terminal methyl groups are disordered.