OH + molecules are an important class of reactions in combustion and atmospheric chemistry. Consequently, numerous studies have measured rate constants for these processes over an extended temperature range. A large majority of these experimental studies have utilized the decay of [OH] profiles (monitored either by absorption or laser-induced fluorescence) to obtain total rate constants. However, there are limited direct measurements of channel specific rate constants in this important class of reactions, particularly at combustion relevant temperatures. In the present experiments, we have directly measured site-specific rate constants for abstraction of the secondary CH bond in OH + C₃H₈ at high temperatures. Atomic resonance absorption spectrometry (ARAS) was used to monitor the formation of H-atoms from shock-heated mixtures of tert-butylhydroperoxide and C₃H₈ at high temperatures. Simulations for the experimental H-atom profiles are sensitive only to abstraction of the secondary CH bond leading to unambiguous measurements of the rate constants for this reaction. Over the T-range, 921 K < T < 1146 K, rate constants from the present experiments for OH + C₃H₈ → H₂O + i-C₃H₇ can be represented by the Arrhenius expression,

$k=\left(3.935\pm 1.387\right)\times {10}^{-11}\text{exp}\left(-1681\pm 362\mathrm{K}/T\right)\mathrm{c}{\mathrm{m}}^3\text{molecul}{\mathrm{e}}^{-1}{\mathrm{s}}^{-1}$

Simulations of the lower temperature data (T < 1000 K) indicate that the H-atom profiles are also influenced to a minor extent by the thermal dissociation of iso-propyl, i-C₃H₇ → H + C₃H₆, at short time-scales. Direct dynamics calculations were performed to examine in greater detail the potential role of prompt dissociations of i-C₃H₇ and n-C₃H₇ (formed from the title reaction) in interpreting the lower temperature (< 1000 K) data from the present work. These simulations suggest that prompt dissociation of propyl radicals does not influence the present experimental observations but has a minor influence on higher temperature combustion simulations.

OH +分子是燃烧和大气化学中的重要反应类别。因此，许多研究已经在扩展的温度范围内测量了这些过程的速率常数。这些实验研究中的绝大多数都利用了[OH]谱的衰减（通过吸收或激光诱导的荧光进行监测）来获得总速率常数。然而，在这一重要的反应类别中，特别是在与燃烧有关的温度下，对通道比速率常数的直接测量是有限的。在目前的实验中，我们已经直接测量了特定位置的速率常数，以提取OH + C ₃ H ₈中的次要C H键在高温下。原子共振吸收光谱法（ARAS）用于监测高温下叔丁基氢过氧化物和C ₃ H _8的混合物受激加热的H原子的形成。实验性H原子分布图的模拟仅对抽象C H键敏感，从而导致对该反应速率常数的明确测量。在921 K < T  <1146 K的T范围内， 当前实验中OH + C ₃ H ₈  →H ₂ O + iC ₃ H _7的速率常数可以用Arrhenius表达式表示，

$ķ=（3.935\pm 1.387）\times {10}^{-11}\text{经验值}（-1681\pm 362\mathrm{ķ}/Ť）\mathrm{C}{\mathrm{米}}^3\text{分子的}{\mathrm{Ë}}^{-\mathrm{1个}}{\mathrm{s}}^{-\mathrm{1个}}$

较低温度数据的模拟（T  <1000 K）表明，异丙基iC ₃ H ₇  →H + C ₃ H ₆的热解离在短时间内对H原子分布也有较小的影响-秤。进行了直接动力学计算，以更详细地研究iC ₃ H ₇和nC ₃ H ₇迅速解离的潜在作用（由标题反应形成）解释当前工作的较低温度（<1000 K）数据。这些模拟表明，丙基自由基的迅速解离不会影响目前的实验观察结果，但对较高温度的燃烧模拟影响较小。