Knyazev Vadim D, Popov Konstantin V
Research Center for Chemical Kinetics, Department of Chemistry, The Catholic University of America, Washington, District of Columbia 20064, United States.
J Phys Chem A. 2015 Jul 16;119(28):7418-29. doi: 10.1021/acs.jpca.5b00644. Epub 2015 Mar 24.
The kinetics of the self-reaction of cyclopentadienyl radicals (c-C5H5) was studied by laser photolysis/photoionization mass spectroscopy. Overall rate constants were obtained in direct real-time experiments in the temperature region 304-600 K and at bath gas densities of (3.00-12.0) × 10(16) molecules cm(-3). The room-temperature value of the rate constant, (3.98 ± 0.41) × 10(-10) cm(3) molecule(-1) s(-1), is significantly higher than the rate constants for most hydrocarbon radical-radical reactions and coincides with the estimated collision rate. The observed overall c-C5H5 + c-C5H5 rate constant demonstrates an unprecedented strong negative temperature dependence: k1 = 2.9 × 10(-12) exp(+1489 K/T) cm(3) molecule(-1) s(-1), with estimated uncertainty increasing with temperature, from 13% at 304 to 32% at 600 K. Formation of C10H10 as the primary product of cyclopentadienyl self-reaction was observed. In additional experiments performed at the temperature of 800 K, formation of C10H10, C10H9, and C10H8 was observed. Final product analysis by gas chromatography/mass spectrometry detected two isomers of C10H8 at 800 K: naphthalene (major) and azulene (minor).
通过激光光解/光电离质谱研究了环戊二烯基自由基（c-C5H5）的自反应动力学。在304 - 600 K的温度范围内以及（3.00 - 12.0）× 10(16) 分子 cm(-3) 的浴气密度下，通过直接实时实验获得了总速率常数。速率常数的室温值为（3.98 ± 0.41）× 10(-10) cm(3) 分子(-1) s(-1)，显著高于大多数烃类自由基-自由基反应的速率常数，并且与估计的碰撞速率相符。观察到的c-C5H5 + c-C5H5总速率常数呈现出前所未有的强烈负温度依赖性：k1 = 2.9 × 10(-12) exp(+1489 K/T) cm(3) 分子(-1) s(-1)，估计的不确定性随温度增加，从304 K时的13%增加到600 K时的32%。观察到环戊二烯基自反应的主要产物为C10H10。在800 K温度下进行的额外实验中，观察到了C10H10、C10H9和C10H8的形成。通过气相色谱/质谱进行的最终产物分析在800 K时检测到了C10H8的两种异构体：萘（主要）和薁（次要）。
