The temperature- and viscosity-dependent rotational isomerization time constant (τ_rot) along the C–C˙ bond of CF₂BrCF₂ radical in solution was measured using femtosecond infrared spectroscopy after photodissociating the I atom from CF₂BrCF₂I. Three density functional theory (DFT) functionals, ωB97XD, APFD, and B3LYP were used with the aug-cc-pVTZ basis set to calculate the required parameters in calculating τ_rot using Kramers’ theory of reaction rates. The measured τ_rot was consistent with the value calculated using the vibrational frequencies and rotational barriers of the related compounds calculated by DFT method with ωB97XD/aug-cc-pVTZ. Kramers’ theory calculation of τ_rot was further verified by an experimental measurement for CF₃CF₂CF₂˙ in CCl₄ at 293 K. The τ_rot along the C–C(˙) bond of ethyl radical and ethane derivatives in solution can be reliably estimated by Kramers’ theory combined with DFT calculations using the ωB97XD functional and aug-cc-pVTZ basis set.

中文翻译：

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测定溶液中沿碳-碳单键的旋转异构化速率


在 I 原子与 CF 2 BrCF 2 进行光解离后，使用飞秒红外光谱法测量了 I 原子与 CF₂BrCF ₂ 自由基在溶液中沿 C-C ̇ 键的温度和粘度依赖性旋转异构化时间常数 （τ_rot）I. 三种密度泛函理论 （DFT） 泛函，ωB97XD、APFD 和 B3LYP 与 aug-cc-pVTZ 基集一起使用，以计算使用 Kramers 反应速率理论计算 τ_rot 所需的参数。测得的 τ_腐烂与使用 ωB97XD/aug-cc-pVTZ 的 DFT 方法计算的相关化合物的振动频率和旋转势垒计算的值一致。Kramers 对 τ_腐烂的理论计算通过在 293 K 下 CCl₄ 中 CF₃、_{CF 2}、CF₂ ̇ 的实验测量得到进一步验证。乙基自由基和乙烷衍生物在溶液中沿 C-C（ ̇） 键的 τ_腐烂可以通过 Kramers 理论结合 ωB97XD 泛函和 aug-cc-pVTZ 基集的 DFT 计算来可靠地估计。