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

Arunan, E and Vijayalakshmi, SP and Valera, R and Setser, DW (2002) Infrared chemiluminescence: Evidence for adduct formation in the H+CH2XI reaction and studies of the N+CH2X (X=Cl/F/I/H) reactions. In: Physical Chemistry Chemical Physics, 4 (1). pp. 51-59.

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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(upsilon) distribution from the H + CH2ClI reaction was P-1-P-5 = 25 : 29 : 26 : 13 : 7. The rate constant for the HCl(upsilon) formation channel is estimated to be 4 times smaller than that for the H + Cl-2 reaction. The highest HCl(upsilon) 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(upsilon) distribution of P-1-P-3 = 77 : 15 : 8. The C-F bond energy in CH2FI is estimated to be less than or equal to 460.2 kJ mol(-1), based on the highest HF(upsilon) level observed, the upper bound being the same as that of F-CH3. When N atoms are added to the flow reactor, the HCl(upsilon) 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.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Keywords: Bond-Dissociation Energies;Absorption Cross-Sections;Hydrogen-Atoms;Ab-Initio;Temperature-Dependence;Polyatomic-Molecules;Branching Ratios;Chlorine Atoms;Alkyl Iodides;Hcn.
Department/Centre: Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 25 Aug 2009 07:10
Last Modified: 19 Sep 2010 05:00
URI: http://eprints.iisc.ernet.in/id/eprint/18158

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