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The gas phase aldose‐ketone isomerization mechanism: Direct interconversion of the model hydroxycarbonyls 2‐hydroxypropanal and hydroxyacetone
Author(s) -
Sun Jing,
So Sui,
da Silva Gabriel
Publication year - 2017
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25434
Subject(s) - isomerization , chemistry , ketose , ketone , photochemistry , reaction mechanism , computational chemistry , aldose , organic chemistry , catalysis , glycoside
We report a novel mechanism for the interconversion of 2‐hydroxypropanal with its more‐stable ketone isomer hydroxyacetone. Reaction proceeds via concerted transfer of two H atoms, requires a barrier of only ∼40 kcal mol −1 , bypasses the enediol intermediate, and is general for α‐hydroxy carbonyls. A similar isomerization mechanism is shown to persist for β, γ, and δ‐hydroxy carbonyls; these compounds are skeletal forms of the monosaccharides and this work, therefore, discloses the gas‐phase mechanism for aldose‐ketose isomerization. As an example, the isomerization of glyceraldehyde to dihydroxyacetone is shown to proceed via this mechanism with a barrier of 31 kcal mol −1 . Rate coefficients and thermochemical properties are reported for the isomerization of 2‐hydroxypropanal and hydroxyacetone for use in detailed kinetic models. Additionally, RRKM theory k ( E ) values for this reaction suggest that it may transpire in the troposphere following solar excitation.