Sorbitol dehydration in a ZnCl2 molten salt hydrate medium: molecular modeling

Li, Jianrong, Buijs, Wem, Berger, Rob J., Moulijn, Jacob and Makkee, Michiel 2013. Sorbitol dehydration in a ZnCl2 molten salt hydrate medium: molecular modeling. Catalysis Science & Technology 4 (1) , pp. 152-163. 10.1039/C3CY00686G

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Abstract

A molecular modelling study, using standard DFT B3LYP/6-31G*, was carried out to develop a better understanding of sorbitol dehydration into isosorbide in ZnCl2 molten salt hydrate medium. Catalysis of sorbitol dehydration by ZnCl2 most likely starts with complexation of the sugar alcohol functions to Zn, followed by an internal SN2 mechanism of a secondary alcohol function attacking a primary alcohol function with the Zn-complex acting as a favourable leaving group. The dehydration reactions to 1,4- and 3,6-anhydrosorbitol show a very similar activation barrier in good accordance with experimental results. The same holds for the formation of isosorbide from 1,4- and 3,6-anhydrosorbitol, albeit with a slightly higher activation barrier. The relative level of the activation barriers reflects the increased strain in the sorbitol skeleton in the corresponding transition states. ZnCl2 turns the dehydration reaction from an endothermic one to an exothermic one by forming a strong complex with the released water. Finally, the ZnCl2–H2O system has been compared with HCl–H2O, which could have been an alternative; it, however, turned out not to be the case.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	Royal Society of Chemistry
ISSN:	2044-4753
Date of Acceptance:	16 October 2013
Last Modified:	04 Jun 2017 08:12
URI:	https://orca.cardiff.ac.uk/id/eprint/74316

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