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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Laser Flash Photolysis Study of Chlorofluorocarbene
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Laser Flash Photolysis Study of Chlorofluorocarbene

机译：氯氟卡宾的激光闪光光解研究

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摘要

10-exo-Fluoro-10'-endo-chlorotricylco[4.3.1.0~(1,6)]decadiene-2,4 (1) was synthesized. Continuous photolysis of 1 (300 nm) generates chlorofluorocarbene 2, which can be intercepted with tetramethylethylene (TME) to form the expected cyclopropane 3. Laser flash photolysis (LFP) of 1 (308 nm) in cyclohexane at ambient temperature does not result in the direct detection of 2 by time-resolved UV-vis spectroscopy. However, LFP of 1 in the presence of pyridine produces the intense transient absorption of ylide 4 at 450 nm. The absolute rate constant of reaction of 2 with pyridine is 8.0 * 10~9 M~(-1) s~(-1) in cyclohexane. LFP (266 nm) of 1 in heptane at ambient temperature produces a transient species with a C-F vibration at 1142 cm~(-1) and a lifetime of 2.5 μs at ambient temperature. The carrier of the transient absorption is assigned to carbene 2 on the basis of density functional theory (DFT) calculations and on the basis of its kinetic behavior. The absolute rate constant of reaction of carbene 2 with TME was determined by monitoring the transient absorption of ylide 4 (Freon-113) or by time-resolved IR spectroscopy (heptane) to give values of 1.1 * 10~8 M~(-1) s~(-1) and 2.9 * 10~8 M~(-1) s~(-1), respectively. This is the first measurement of a bimolecular ground-state singlet carbene reaction by both time-resolved UV-vis and IR spectroscopy. The value determined by the time-resolved IR measurement is more accurate than that from the ylide probe technique.
机译：合成了10-exo-Fluoro-10'-endo-chlorotricylco [4.3.1.0〜（1,6）] decadiene-2,4（1）。连续进行1（300 nm）的光解会生成氯氟碳烯2，可以用四甲基乙烯（TME）截取该氯氟碳烯2，以形成预期的环丙烷3。在环境温度下于环己烷中进行1（308 nm）的激光快速光解（LFP）不会导致通过时间分辨紫外可见光谱法直接检测2。但是，在吡啶存在下LFP为1会在450 nm处产生强烈的瞬态吸收叶立德4。 2与吡啶反应的绝对速率常数为8.0 * 10〜9 M〜（-1）s〜（-1）。在室温下于庚烷中的LFP（266 nm）为1，会产生一个瞬态物质，其在1142 cm〜（-1）处具有C-F振动，在环境温度下的寿命为2.5μs。根据密度泛函理论（DFT）计算并根据其动力学行为，将瞬态吸收的载体分配给卡宾2。卡宾2与TME的绝对反应速率常数是通过监测叶立德4（Freon-113）的瞬时吸收或通过时间分辨IR光谱（庚烷）得出1.1 * 10〜8 M〜（-1）来确定的）s〜（-1）和2.9 * 10〜8 M〜（-1）s〜（-1）。这是通过时间分辨紫外可见光谱和红外光谱对双分子基态单线态卡宾反应的首次测量。由时间分辨的IR测量确定的值比由ylide探针技术确定的值更准确。

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