Infrared study of the adsorption of cyclohexanone on silica immersed in 2,2,4-trimethylpentane

Abstract

Infrared spectra are reported of silica preheated at 423 K and subsequently immersed in solutions of cyclohexanone in 2,2,4-trimethylpentane. Cyclohexanone was adsorbed onto isolated silanol group sites predominantly via the formation of hydrogen bonds between individual hydroxyl groups and single cyclohexanone molecules. A few pairs of isolated silanol groups were sufficiently close together to simultaneously form pairs of hydrogen bonds with single adsorbate molecules. Three types of surface hydroxyl groups which interacted laterally with adjacent surface hydroxyl groups also provided sites for the adsorption of cyclohexanone. Each cyclohexanone molecule was adsorbed onto a pair of adjacent interacting hydroxyl groups by the simultaneous formation of two hydrogen bonds. At low surface coverages the adsorption of cyclohexanone onto pairs of surface hydroxyl groups predominated over the adsorption onto single isolated silanol groups. The latter became more significant as the surface coverage was increased.