UV Photolysis of Pyrazine and the Production of Hydrogen Isocyanide,The Journal of Physical Chemistry A

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UV Photolysis of Pyrazine and the Production of Hydrogen Isocyanide
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2018-10-30 00:00:00 , DOI: 10.1021/acs.jpca.8b09179
Michael J. Wilhelm ₁ , George A. Petersson ₂ , Jonathan M. Smith ₁ , Drew Behrendt ₁ , Jianqiang Ma ₁ , Laura Letendre ₃ , Hai-Lung Dai ₁

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Photolysis of the diazine heterocycle, pyrazine, following irradiation at 308, 248, and 193 nm was examined using nanosecond time-resolved Fourier transform infrared emission spectroscopy. The resulting time-resolved IR emission spectra reveal that for 308 and 248 nm vibrationally highly excited pyrazine is produced, but no photolysis products were detected. However, at 193 nm excitation, the measured IR emission spectra consist solely of resonances originating from rovibrationally excited photofragments, including acetylene (HCCH), hydrogen cyanide (HCN), and hydrogen isocyanide (HNC), indicating that photofragmentation proceeds from vibrationally highly excited pyrazine on the ground electronic state. Spectral fit analysis of the time-resolved HCN and HNC IR emission band shapes and intensities allowed an estimate of the nascent product population distributions, from which a lower bound estimate of the HNC/HCN branching ratio was deduced as Φ ≥ 0.07. Additionally, ab initio calculations were performed in order to examine the propensity of photoinduced reactions on the ground- and lowest-energy excited-state surfaces. The calculations provide a basis for understanding the wavelength dependence of the UV photolysis of pyrazine, the photolytic production of HNC, and also explain previous experimental observations in the literature.

中文翻译：

吡嗪的紫外光解与异氰酸氢的产生

使用纳秒级时间分辨傅里叶变换红外发射光谱法检查了在308、248和193 nm照射后，二嗪杂环，吡嗪的光解作用。产生的时间分辨的红外发射光谱表明，对于308和248 nm，产生了振动高度激发的吡嗪，但未检测到光解产物。然而，在193 nm激发下，测得的IR发射光谱仅由源自激发激发的光碎屑（包括乙炔（HCCH），氰化氢（HCN）和异氰化氢（HNC））的共振组成，表明光碎屑源自振动高度激发的吡嗪在地面上的电子状态。通过对时间分辨的HCN和HNC IR发射带形状和强度进行光谱拟合分析，可以估算新生产品的分布，从中可以得出HNC / HCN分支比的下限估算为Φ≥0.07。另外，进行了从头算以检查在基态和最低能量激发态表面上光诱导反应的倾向。该计算为理解吡嗪的UV光解的波长依赖性，HNC的光解产物提供了基础，并且还解释了文献中先前的实验观察结果。从头开始进行计算，以检查在基态和最低能量激发态表面上光诱导反应的倾向。该计算为理解吡嗪的UV光解的波长依赖性，HNC的光解产物提供了基础，并且还解释了文献中先前的实验观察结果。从头开始进行计算，以检查在基态和最低能量激发态表面上光诱导反应的倾向。该计算为理解吡嗪的UV光解的波长依赖性，HNC的光解产物提供了基础，并且还解释了文献中先前的实验观察结果。

更新日期：2018-10-30

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