کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9590834 | 1507021 | 2005 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Theoretical enthalpies of formation for atmospheric hydroxycarbonyls
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
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چکیده انگلیسی
The G3 and DFT (B3LYP) quantum chemical methods were applied to estimate enthalpies of formation for the closed-shell molecules glycolaldehyde (HOCH2C(O)H) and hydroxyacetone (HOCH2C(O)CH3) as well as for the related free radicals hydroxy-acetyl (HOCH2CO) and hydroxy-vinoxy (HOCHC(O)H). These hydroxycarbonyls are important reaction intermediates formed in the photo-oxidation of isoprene which is the most abundant biogenic hydrocarbon in the atmosphere. Several isodesmic reactions were used in the computations as working chemical reactions, giving results in good agreement with each other. The following standard enthalpies of formation are recommended as best values (in kcal molâ1): ÎfH°298 (glycolaldehyde)=â75.6±0.8, ÎfH°298 (hydroxyacetone)=â89.1±0.8, ÎfH°298 (HOCH2CO)=â37.7±1.2 and ÎfH°298 (HOCHC(O)H)=â50.8±1.2, where the errors given are proposed as 1Ï. The ÎfH°298 values obtained imply that the presence of the OH-group significantly reduces the C-H and C-C bond dissociation energies at the alpha position in the glycolaldehyde and hydroxyacetone molecules, but has no effect on the bond strengths at the beta position. Inferences for atmospheric chemistry are briefly discussed.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Structure: THEOCHEM - Volume 713, Issues 1â3, 14 January 2005, Pages 119-125
Journal: Journal of Molecular Structure: THEOCHEM - Volume 713, Issues 1â3, 14 January 2005, Pages 119-125
نویسندگان
J. Espinosa-GarcÃa, Sándor Dóbé,