A density functional theory model of mechanically activated silyl ester hydrolysis.

Pill, Michael F., Schmidt, Sebastian W., Beyer, Martin, Clausen-Schaumann, Hauke and Kersch, Alfred (2014) A density functional theory model of mechanically activated silyl ester hydrolysis. Journal of Chemical Physics, 140 (4).

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Abstract

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutral reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ mol(-1), which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters. (C) 2014 AIP Publishing LLC.

Document Type: Article
Additional Information: Times Cited: 1 Beyer, Martin/A-5793-2009 Beyer, Martin/0000-0001-9373-9266 0 1
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
ISSN: 0021-9606
Projects: Future Ocean
Date Deposited: 30 Mar 2015 12:40
Last Modified: 30 Mar 2015 12:40
URI: http://oceanrep.geomar.de/id/eprint/28144

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