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Mechanism and theory of d-glucopyranose homogeneous acid catalysis in the aqueous solution phase

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Show simple item record Ghosh, Manik Kumer Howard, Mícheál Howard Dussan, Karla Dooley, Stephen 2019-10-10T10:15:23Z 2019
dc.description peer-reviewed en_US
dc.description.abstract A detailed systematic theoretical study of the mechanism of the homogeneous Brønsted -acid catalysis of D-glucose in aqueous solution phase ("acid hydrolysis") is reported. G4MP2 with the SMD solvation model at B3LYP/6-31G(2df,p) are employed to compute the free energies of the molecular and ionic species pertaining to the isomerization, protonation, hydrogen cation transfer and decomposition processes of D-glucopyranose in aqueous solution phase. This information is used to hypothesise a reaction mechanism that is of improved accuracy and completeness from the existing art. It is found that rotation of the D-glucose alkyl carbon-carbon bond is a facile process and is very important to the subsequent catalytic mechanism. This rotation produces two rotameric isomers which are of notably different thermodynamic stability and reactivity, even with regard to the products of this acid catalysis. As a low energy process =E2 = ~3.8 6.7 kcal/mol), the alkyl carbon-carbon bond may rotate toward the hydroxyl group at the adjacent "4" position reducing the energy required to protonate that position by 3.0 7.2 kcal/mol (or 15 30 %). The combination of two rotomeric isomers with the six structural isomers owing to the oxygen atoms, means that protonated D-glucose cations embark on a complex competition of interconversion and decomposition that is both thermodynamically and kinetically influenced. The calculations support the hypothesis that the acid-catalysed hydrolysis of D-glucose may yield a number of platform chemicals that have not previously been suggested. These include the prospect of three isomers of 5-hydroxymethylfurfural (HMF); 5- (hydroxymethyl)furan-2-carbaldehyde, 5-(hydroxymethyl)furan-3-carbaldehyde and 5-(hydroxymethyl)furan-4- carbaldehyde. Vibrational spectra of these HMF isomers are also computed and compared to experimentally determined infrared spectra of "humins". On this basis, it is cautiously speculated that the alternative HMF isomers, may be monomeric constituent of the polymeric "humins". en_US
dc.language.iso eng en_US
dc.publisher Royal Society of Chemistry en_US
dc.relation 13SIRG2185 en_US
dc.relation.ispartofseries Physical Chemistry Chemical Physics;21, pp. 17993-18011
dc.relation.uri 10.1039/C8CP07224H
dc.rights © 2019 Royal Society of Chemistry. Personal use of this material is permitted. Permission from Royal Society of Chemistry must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works en_US
dc.subject D-glucose en_US
dc.subject homogeneous acid en_US
dc.title Mechanism and theory of d-glucopyranose homogeneous acid catalysis in the aqueous solution phase en_US
dc.type info:eu-repo/semantics/article en_US
dc.type.supercollection all_ul_research en_US
dc.type.supercollection ul_published_reviewed en_US
dc.identifier.doi 10.1039/C8CP07224H
dc.contributor.sponsor SFI en_US
dc.contributor.sponsor Irish Centre for High-End Computing (ICHEC) en_US
dc.relation.projectid SFI en_US
dc.relation.projectid 13/SIRG/2185 en_US
dc.relation.projectid 16/ERCD/3685 en_US 2020-07-15
dc.embargo.terms 2020-07-15 en_US
dc.rights.accessrights info:eu-repo/semantics/openAccess en_US

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