Issue 1, 2002

Infrared chemiluminescence: Evidence for adduct formation in the H + CH2XI reaction and studies of the N + CH2X (X = Cl/F/I/H) reactions

Abstract

Infrared chemiluminescence from a flow reactor has been used to study the H + CH2XI and N + CH2X (X = Cl, F, I, H) reactions at 300 K. Both the HI + CH2Cl and HCl + CH2I channels were identified for the H + CH2ClI reaction. The HCl channel involves adduct, HICH2Cl, formation as confirmed by the D + CH2ClI reaction, which gave both HCl and DCl products. The nascent HCl(v) distribution from the H + CH2ClI reaction was P1–P5 = 25 : 29 : 26 : 13 : 7. The rate constant for the HCl(v) formation channel is estimated to be 4 times smaller than that for the H + Cl2 reaction. The highest HCl(v) level observed from the H + CH2ClI reaction implies that the C–Cl bond energy is 50.2 kJ mol−1 lower than that of the Cl–CH3 bond, which is in modest agreement with recent theoretical estimates. The H + CH2FI reaction gave a HF(v) distribution of P1–P3 = 77 : 15 : 8. The C–F bond energy in CH2FI is estimated to be ≤460.2 kJ mol−1, based on the highest HF(v) level observed, the upper bound being the same as that of F–CH3. When N atoms are added to the flow reactor, the HCl(v) emission intensities from H + CH2ClI increased by up to 2-fold, which is attributed to the N + CH2Cl → HCl + HCN reaction. Concomitant weak emission from HCN and HNC could also be observed; however, the main product channel is thought to be NCH2 + Cl. Strong visible CN(A–X) emission was also observed when H/N/CH2XI were present in the reactor. If the CH2X radicals were produced by the F + CH3X reaction in the presence of N atoms, similar results were obtained. The N + CH2N reaction is proposed as the first step that leads to CN(A) formation with NCN as an intermediate.

Article information

Article type
Paper
Submitted
14 Sep 2001
Accepted
26 Oct 2001
First published
06 Dec 2001

Phys. Chem. Chem. Phys., 2002,4, 51-59

Infrared chemiluminescence: Evidence for adduct formation in the H + CH2XI reaction and studies of the N + CH2X (X = Cl/F/I/H) reactions

E. Arunan, S. P. Vijayalakshmi, R. Valera and D. W. Setser, Phys. Chem. Chem. Phys., 2002, 4, 51 DOI: 10.1039/B108362G

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