2-DIMENSIONAL CRYSTALLINE-STRUCTURES AND PHOTOCHEMICAL BEHAVIOR OF CINNAMATE MONOLAYERS ON WATER SURFACES

A direct relationship between the structures of two-dimensional (2-D) crystallites of 4-octadecyloxy-E-cinnamic acid and 4-octadecyloxy-E-ci nnamamide amphiphiles at the air-water interface and their photochemic al behavior, is presented. The detailed packing arrangements of the mo nolayers were determined, close to the atomic level, from the diffract ion pattern measured, in situ on the water surface, by the grazing inc idence X-ray diffraction (GID) technique using synchrotron radiation. The products of the photochemical reaction, performed by irradiating t he monolayer films directly on the water surface, were collected and a nalyzed. While the acid crystallites yield a beta-truxinic acid produc t together with the cis-isomer, the amide undergoes only trans-cis iso merisation, in full agreement with the 2-D crystalline packing arrange ments of the two amphiphiles on the water surface. (C) 1998 Wiley-Liss , Inc.