Computational approach to estimate layer structures of organic derivatives of boehmite Original Research Article

The observed basal spacings of the alkyl derivatives of boehmite, AlO(OH)1−x(OR)x, obtained by the reaction of aluminum metal or aluminum alkoxides with alcohols at 250–300 °C was only slightly affected by the population (x) of the alkyl groups (x=0.39−0.21) (Chem. Mater. 12 (2000) 55). In order to clarify the origin of this independency, the molecular mechanics (MM) calculation was carried out, and the effect of the alkyl population upon the basal spacing of the butyl derivative of boehmite, AlO(OH)1−x(OCH2CH2 CH2CH3)x, was examined in a range of x=0.00–0.30. The calculated results clearly suggested that in the range of x from 0.3 to 0.2, the boehmite derivative has the bilayer arrangement of the alkyl groups with essentially all-trans conformation. In this range, the basal spacing was only slightly affected by the population of the alkyl groups because it is determined by the most crowded part of the assembly of the alkyl chains. Since the alkyl chains are fixed to the host layers through the covalent bonding, decrease in the alkyl population does not affect essential feature of the alkyl derivatives of layered inorganics.