Two-Channel Thermal Unimolecular Decomposition of Alkyl Iodides
Two-Channel Thermal Unimolecular Decomposition of Alkyl Iodides
复制标题
烷基碘的双通道热单分子分解
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
H. Matsui
中科院分区：
文献类型：
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作者：
A. Miyoshi;Noboru Yamauchi;K. Kosaka;M. Koshi;H. Matsui
在950 - 1400 K温度和1 atm压力下，用激波管技术研究了C3-C4碘代烷热单分子分解中C-I键裂变和四中心HI消除之间的竞争。通过原子共振吸收光谱法跟踪碘原子的浓度。对于初级碘化物，在950 - 1100 K的温度下测量绝对速率常数。在950 - 1400 K的温度下，测定了C3和C4烷基碘的所有异构体的C-I键裂变通道的分支分数。从初级碘化物中观察到C−I键裂变通道的分支分数的急剧变化（0.6−0.9）到次级碘化物（0.2 - 0.4），进一步为叔碘化物（<0.05），这主要归因于HI消除通道的阈值能量从初级通道到次级通道的降低（~ 14 kJ mol ~（-1））和从仲到叔（~ 20 kJ mol ~（-1））的碘化物。α-CH 3取代基对活化能的影响。
The competition between the C−I bond fission and the four-center HI elimination in the thermal unimolecular decomposition of C3−C4 alkyl iodides has been investigated at temperatures of 950−1400 K and pressures around 1 atm by a shock tube technique. The concentration of iodine atoms was followed by atomic resonance absorption spectrometry. For primary iodides, the absolute rate constants were measured at temperatures of 950−1100 K. The branching fractions for C−I bond fission channels were determined for all isomers of C3 and C4 alkyl iodides at temperatures of 950−1400 K. A drastic change in the branching fraction for the C−I bond fission channel was observed from primary iodides (0.6−0.9) to secondary iodides (0.2−0.4), and further to tertiary iodide (<0.05), which was mainly ascribed to the lowering of the threshold energy for the HI elimination channel from primary to secondary (by ∼14 kJ mol-1) and from secondary to tertiary (by ∼20 kJ mol-1) iodides. The α-CH3 substituent effect to the activation e...