Abstract:
Infra-red spectroscopy has been used to investigate the structure of the chemisorbed species which
are formed when CH3OH, CH2DOH, CHD-OH and CD3OH react with silica. Force constant
calculations utilizing only the CH and CD stretching modes have been used to show that the strongest
spectral features can be assigned to an unsymmetrical surface SiOMe group which has one strong and
two weak CH bonds. Some additional spectral features which reversibly grew in intensity with
increasing sample temperatures have been assigned to a symmetrical SiOMe species which exists in
equilibrium with unsymmetrical SiOMe. It has been suggested that the infra-red bands of sym
metrical SiOMe are probably hot bands arising from transitions from the first vibrationally excited
state of the SiOC bending mode such that rapid flipping of the SiOC bond can occur in this excited
state.
