Silylation of cellobiose as a model reaction for the synthesis of silylated cellulose. A DFT and PM3 approach.
Published: 31 October 2011 by Molecular Diversity Preservation International in Proceedings of The 15th International Electronic Conference on Synthetic Organic Chemistry in The 15th International Electronic Conference on Synthetic Organic Chemistry session Computational Chemistry
Molecular Diversity Preservation International, 10.3390/ecsoc-15-00572
Abstract: The object of the present study is the isodesmic reaction of cellobiose (the repeating unit in cellulose) with different kinds of silanes, R-SiH3, to form silylated cellobiose (Cello-SiH3) and the corresponding alcohols (R-OH). The size and the chemical reactivity of the substituent R is varied as well as the position where O-silylation at the cellobiose takes place. In contrast to experimental observations where the O6 position is favored for silylation, for the computed reactions, energy differences are smaller than 3 kcal/mol for the different positions at the B3LYP/6-311G* as well as at the B3LYP/6-311+G* level of theory. Depending on the silane, reaction energies in a range from -17 kcal/mol (R=NHSiH3) and +18 kcal/mol (R=F) have been calculated. In addition, semi-empirical calculations on the PM3 level of theory have been performed. These results are set into contrast with the results derived from DFT calculations to assess whether semi-empirical methods may be useful for the description of larger systems containing silylated cellobiose units. Acknowledgements: The research leading to these results has received funding from the European Community\'s Seventh Framework Programme [FP7/2007–2013] under grant agreement no. 214015 (S.S. and H.M.A.E.) and no. 214653.
Keywords: model, cellulose, DFT, Silane, Kcal/mol, B3lyp/6, SiH3, silylated cellobiose