期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 4, 期 19, 页码 4663-4668出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/b201883g
关键词
-
The activation energies for the methyl radical addition to CH2O, CH3CHO, and (CH3)(2)CO, are small and around 28, 29, and 40 kJ mol(-1), respectively. For the addition of primary alkyl radicals to formaldehyde and higher aldehyde homologues, we find significantly lower activation barriers of (20 +/- 4) kJ mol(-1) and (27 +/- 2) kJ mol(-1), respectively. An almost negligible activation barrier of about 5 kJ mol(-1) was found for the secondary radical addition to formaldehyde. In the case of addition of a tertiary radical to formaldehyde no activation barrier could be identified. Generally, methyl addition reactions to carbonyls will compete with hydrogen abstraction reactions. For larger alkyl radicals addition to carbonyls dominates over the direct H-atom abstraction. A self-consistent set of standard enthalpies of formation Delta(f)Hdegrees for saturated alkoxy (CnH2n+1O., where n less than or equal to 5) radicals was obtained by the modified Gaussian-3(G3(MP2)//B3LYP) ab initio molecular orbital theory. The calculated heats of formations are in good agreement with literature values estimated from O-H bond dissociation energies. The expected maximum error of the calculated Delta(f)Hdegrees is less than 4 kJ mol(-1). The primary, secondary, and tertiary alkoxy group values (GV) were evaluated from the ab initio Delta(f)Hdegrees-s with a standard deviation of 1.2 kJ mol(-1).
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据