Hydrolysis and esterification in organically modified alkoxysilanes: A 29Si NMR investigation of methyltrimethoxysilane†

Todd M. Alam, Roger A. Assink, Douglas A. Loy

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65 Scopus citations


High-resolution 29Si NMR was used to investigate the acid-catalyzed hydrolysis and esterification reactions of methyltrimethoxysilane (MTMS) in methanol. The INEPT experiment, adapted for spin systems with multiple heteronuclear coupling constants, was used to assign the closely spaced resonances of the MTMS hydrolysis products. Due to the rapid reaction rates, only the pseudoequilibrium concentration distribution for the resulting hydrolysis products could be determined. Models based on thermodynamically statistical distributions, irreversible hydrolysis reactions, and reversible hydrolysis reactions were nearly equally successful in accounting for the concentration distributions over a wide range of H2O/Si ratios (Rw) and temperatures. However, preparation of hydrolyzed MTMS in a nonpseudoequilibrium state unequivocally demonstrated the reversibility of hydrolysis reactions on a short time scale. By measuring the extent of reaction of MTMS systems at high water concentrations, the ratio of the hydrolysis to esterification rate constant was determined to be approximately 100.

Original languageEnglish (US)
Pages (from-to)2366-2374
Number of pages9
JournalChemistry of Materials
Issue number9
StatePublished - Sep 1996

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry


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