Infrared study of adsorption of acetophenones on silica–alumina

Infrared spectra are reported of acetophenone and 4-methoxyacetophenone adsorbed on silica–alumina catalyst. The dominant modes of adsorption involved ligation via carbonyl groups to Lewis acidic Al 3+ sites and H-bonding of surface silanol groups to carbonyl groups or aromatic rings. Isotopic H/D e...

Full description

Saved in:
Bibliographic Details
Published in:Journal of molecular catalysis. A, Chemical Chemical, 1998-09, Vol.135 (1), p.63-73
Main Authors: Ahmad, Imtiaz, Anderson, James A, Rochester, Colin H, Dines, Trevor J
Format: Article
Language:English
Subjects:
Acetophenones
Brønsted sites
Catalysis
Catalysts: preparations and properties
Chemistry
Exact sciences and technology
General and physical chemistry
Infrared spectra
Silica–alumina catalyst
Solid-gas interface
Surface physical chemistry
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Infrared spectra are reported of acetophenone and 4-methoxyacetophenone adsorbed on silica–alumina catalyst. The dominant modes of adsorption involved ligation via carbonyl groups to Lewis acidic Al 3+ sites and H-bonding of surface silanol groups to carbonyl groups or aromatic rings. Isotopic H/D exchange between SiOH groups and CD 3 groups or SiOD and CH 3 occurred for acetophenone probably via an enolisation mechanism, although no enolic species could be detected. There was also little evidence for condensation reactions. Band positions for adsorbed acetophenones compared with the predictions of Hartree–Fock calculations suggested that acetophenone was not protonated, but 4-methoxyacetophenone was protonated by Brønsted acidic hydroxy groups for which −6.15≤ H 0≤−4.81.
ISSN:1381-1169
1873-314X
DOI:10.1016/S1381-1169(97)00289-6