KINETICS OF ALPHA-HYDROGEN AND BETA-HYDROGEN ABSTRACTION FROM C2H5CL BY BR ATOMS - ESTIMATE OF C-H BOND-DISSOCIATION ENERGIES AND HEATS OF FORMATION OF CH3CHCL AND CH2CH2CL RADICALS
KINETICS OF ALPHA-HYDROGEN AND BETA-HYDROGEN ABSTRACTION FROM C2H5CL BY BR ATOMS - ESTIMATE OF C-H BOND-DISSOCIATION ENERGIES AND HEATS OF FORMATION OF CH3CHCL AND CH2CH2CL RADICALS
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DOI：
10.1021/j100365a037
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发表时间：
1990-01-25
影响因子：
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通讯作者：
TSCHUIKOWROUX, E
中科院分区：
文献类型：
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作者：
MIYOKAWA, K;TSCHUIKOWROUX, E
在乙烷存在和不存在的情况下，在较宽的温度范围内研究了氯乙烷的气相光溴化反应。在40~150℃范围内，重新测定了CH_3CH_2C_1相对于C_2H_6的抽氢速率常数。在70-150℃范围内，用电子俘获检测测定了/3-氢的内竞争抽氢。将相对速率与已知的C2H6溴化速率参数[log(/cm3mo1·S‘1)=14.14±0.06，E=13.66±0.14kcal mol1]相结合，得到绝对速率常数(cm3mo1·S’1)k(A)=I12，71±0.06exp[-(9.95±0.14)//？7]和Gb(/3)=1012·60*0.07exp[-(14.14±0.15)//？7]，根据热化学和动力学数据，得到了C_2H_5C_1的自由基生成热和CH键的解离能(K_(Cal)~(-1))：A//f(CH_3CHCl)=17.6±1，7&gT；(CH_3CHCl-H)=96.5±1，A/7f(CH_2CH_2Cl)=21.8±1，Gb>；(CH_2C_1CH_2-H)=100.7±1。这些结果与最近用单能电子碰撞法测得的结果相比较令人满意。
The gas-phase photobrominationof ethyl chloride has been investigated over an extended temperature range in the presence and absence of ethane as external competitor. The rate constant for-hydrogen abstraction in CH3CH2C1 was redetermined relative to C2H6 between 40 and 150 C. The abstraction of/3-hydrogen was measured in the internal competition inthe range 70-150 C by use of electron capture detection. The relative rates were combined with the known rate parameters for the bromination of C2H6 [log (/cm3 mol'1 s'1)= 14.14±0.06, E= 13.66±0.14 kcal mol'1] to obtain the absolute rate constants (cm3 mol'1 s'1) k (a)= io12, 71±0· 06 exp [-(9.95±0.14)//? 7] and£(/3)= lO12· 60* 0· 07 exp [-(14.14±0.15)//? 7], where the activation energies are expressed in kcal mol'1. From an assessment of thermochemical and kinetic data the following radical heats of formation and CH bond dissociation energies (kcal mol'1) in C2H5C1 have been obtained: A//f (CH3CHCl)= 17.6±1, 7>(CH3CHC1-H)= 96.5±1 and A/7f (CH2CH2Cl)= 21.8±1,£>(CH2C1CH2-H)= 100.7±1. These results compare satisfactorilywith recent determinations by the monoenergetic electron impact method.