Critical properties of some tetraalkoxysilanes and tetraalkoxytitaniums with branched alkyl radicals

The critical pressures and the critical temperatures of tetraisopropoxytitanium, tetra-tert-butoxytitanium, and tetraisopropoxysilane have been measured. The decomposition of the substances studied begins at temperatures below their critical ones. A pulse-heating method which allows measuring the critical properties of thermally unstable compounds has been used. The times of heating from the beginning of a pulse to the moment of reaching the critical temperature were from 0.03 to 1 ms. The short residence times provided little degradation of the substances in the course of the experiments. The critical constants of tetraalkoxytitaniums and tetraalkoxysilanes with branched and straight alkyl chains have been compared. The experimental critical constants of tetraalkoxytitaniums and tetraalkoxysilanes have also been compared with those calculated using various group-contribution methods.

► Critical constants of branched alkoxysilanes and alkoxytitaniums were measured.
► Branched compounds have lower critical temperatures than straight ones.
► The critical pressures of isomers differ very slightly.