使用光腔衰荡光谱法观察氯原子与XCH2I（X = H、CH3、Cl、Br、I）反应中的加合物。

Observation of adducts in the reaction of Cl atoms with XCH2I (X = H, CH3, Cl, Br, I) using cavity ring-down spectroscopy.

作者信息

Enami Shinichi, Hashimoto Satoshi, Kawasaki Masahiro, Nakano Yukio, Ishiwata Takashi, Tonokura Kenichi, Wallington Timothy J

机构信息

Department of Molecular Engineering and Graduate School of Global Environmental Studies, Kyoto University, Kyoto 615-8510, Japan.

出版信息

J Phys Chem A. 2005 Mar 3;109(8):1587-93. doi: 10.1021/jp047297y.

DOI:10.1021/jp047297y

PMID:16833481

Abstract

The reactions of Cl atoms with XCH2I (X = H, CH3, Cl, Br, I) have been studied using cavity ring-down spectroscopy in 25-125 Torr total pressure of N2 diluent at 250 K. Formation of the XCH2I-Cl adduct is the dominant channel in all reactions. The visible absorption spectrum of the XCH2I-Cl adduct was recorded at 405-632 nm. Absorption cross-sections at 435 nm are as follows (in units of 10(-18) cm2 molecule(-1)): 12 for CH3I, 21 for CH3CH2I, 3.7 for CH2ICl, 7.1 for CH2IBr, and 3.7 for CH2I2. Rate constants for the reaction of Cl with CH3I were determined from rise profiles of the CH3I-Cl adduct. k(Cl + CH3I) increases from (0.4 +/- 0.1) x 10(-11) at 25 Torr to (2.0 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1) at 125 Torr of N2 diluent. There is no discernible reaction of the CH3I-Cl adduct with 5-10 Torr of O2. Evidence for the formation of an adduct following the reaction of Cl atoms with CF3I and CH3Br was sought but not found. Absorption attributable to the formation of the XCH2I-Cl adduct following the reaction of Cl atoms with XCH2I (X = H, CH3, Br, I) was measured as a function of temperature over the range 250-320 K.

摘要

在250 K、总压力为25 - 125 Torr的氮气稀释剂中，利用光腔衰荡光谱法研究了氯原子与XCH₂I（X = H、CH₃、Cl、Br、I）的反应。XCH₂I - Cl加合物的形成是所有反应中的主要通道。在405 - 632 nm记录了XCH₂I - Cl加合物的可见吸收光谱。435 nm处的吸收截面如下（单位为10⁻¹⁸ cm² 分子⁻¹）：CH₃I为12，CH₃CH₂I为21，CH₂ICl为3.7，CH₂IBr为7.1，CH₂I₂为3.7。根据CH₃I - Cl加合物的上升曲线确定了Cl与CH₃I反应的速率常数。在25 Torr氮气稀释剂中，k(Cl + CH₃I)从(0.4 ± 0.1) × 10⁻¹¹ 增加到125 Torr时的(2.0 ± 0.3) × 10⁻¹¹ cm³ 分子⁻¹ s⁻¹。CH₃I - Cl加合物与5 - 10 Torr的O₂没有明显反应。寻找了氯原子与CF₃I和CH₃Br反应后形成加合物的证据，但未找到。测量了氯原子与XCH₂I（X = H、CH₃、Br、I）反应后形成XCH₂I - Cl加合物的吸收随温度在250 - 320 K范围内的变化情况。