1H and 13C NMR observation of the reaction of acetic acid with titanium isopropoxide

Hydrogen and carbon NMR spectroscopy have been used to investigate the chemical modification process of titanium isopropoxide by acetic acid. The spectra confirm the belief that the titanium isopropoxide exchanges isopropyl groups with modifying acetate groups to form a molecule with approximate stoichiometry Ti(OiPr)(2)(OAc)(2). This stoichiometry results even when enough acetic acid is present in solution to allow for significantly higher isopropyl replacement. In addition, progressive esterification to form isopropyl acetate results in a gradually increasing level of condensation and ore-bridging between the Ti oligomers. Throughout the condensation process, the remaining Ti-bound acetate and isopropyl groups maintain an approximate 1:1 ratio, suggesting that ore-bridge formation occurs through a transesterification process. (C) 1999 Elsevier Science S.A. All rights reserved.