کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1389216 982853 2011 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Converting fructose to 5-hydroxymethylfurfural: a quantum mechanics/molecular mechanics study of the mechanism and energetics
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Converting fructose to 5-hydroxymethylfurfural: a quantum mechanics/molecular mechanics study of the mechanism and energetics
چکیده انگلیسی

We studied the energetics of the closed-ring mechanism of the acid-catalysed dehydration of d-fructose to 5-hydroxymethylfurfural (HMF) by carrying out canonical ensemble free-energy calculations using bias-sampling, hybrid Quantum Mechanics/Molecular Mechanics Molecular Dynamics simulations with explicit water solvent at 363 K. The quantum mechanical calculations are performed at the PM3 theory level. We find that the reaction proceeds via intramolecular proton and hydride transfers. Solvent dynamics effects are analysed, and we show that the activation energy for the hydride transfers is due to re-organization of the polar solvent environment. We also find that in some instances intramolecular proton transfer is facilitated by mediating water, whereas in others the presence of quantum mechanical water has no effect. From a micro-kinetic point of view, we find that the rate-determining step of the reaction involves a hydride transfer prior to the third dehydration step, requiring an activation free energy of 31.8 kcal/mol, and the respective rate is found in good agreement with reported experimental values in zeolites. Thermodynamically, the reaction is exothermic by ΔF=20.5kcal/mol.

Figure optionsDownload as PowerPoint slideResearch highlights
► The fructose to 5-hydroxymethylfurfural dehydration mechanism is elucidated.
► Free energy calculations are performed for each elementary step.
► Explicit solvent effects are taken into account.
► Solvent dynamics effects are analysed.
► Quantum mechanical treatment of fructose and all reaction intermediates.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Carbohydrate Research - Volume 346, Issue 5, 1 April 2011, Pages 664–672
نویسندگان
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