Kinetics and mechanism of X + CINO → XCl + NO (X = Cl, F, Br, OH, O, N) from 220 to 450 K. Correlation of reactivity and activation energy with electron affinity of X

J. P.D. Abbatt, D. W. Toohey, F. F. Fenter, P. S. Stevens, William Henry Brune, J. G. Anderson

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Abstract

The rate constants for a series of radical reactions with ClNO, X + ClNO → products where X = Cl, F, Br, OH, O, N, have been measured as a function of temperature in discharge flow systems at pressures between 1 and 2 Torr of helium buffer gas. Radicals were detected by resonance fluorescence (X = Cl, Br, OH, O), laser magnetic resonance (X = OH), and chemical conversion/resonance fluorescence (X = F, N). The rate constants, with units of cm3 molecule-1 s-1 and to 95% confidence level, are for Cl + ClNO → Cl2 + NO, [(6.6±1.2) × 10-11]e(128±46)/T; for F + ClNO → FCl + NO, [(1.4 ±0.4) × 10-10]e(-28±84)/T. for Br + ClNO → BrCl + NO, [(1.5±0.2) × 10-11]e(-52±43)/T; for OH + ClNO → ClOH + NO, [(9.0±4.5) × 10-12]e(-1130±170)/T; for OH + ClNO → HONO + Cl, [(9.2±6.5) × 10-14]e(240±130)/T; for O + ClNO → ClO + NO, [(8.3±0.9) × 10-12]e(-1520 ± 36)/T; and for N + ClNO → NCl + NO, [(9.2 ± 2.2) × 10-12]e(-2250±90)/T. Both the reaction activation energies and the logarithms of the room temperature rate constants are found to correlate strongly with the electron affinity of the radical in such a way that high electron affinity leads to enhanced reactivity. The reactivity trend is rationalized by a frontier orbital interaction dominated by the ease with which electron transfer from the ClNO molecule to the X radical can occur to stabilize a polar transition state, a mechanism shown to be widely prevalent in radical-molecule systems. The propensity for this type of interaction is determined by the energy required for electron transfer which, in this case, is given by IPClNO - EAX, where IP refers to ionization potential and EA to electron affinity. In addition, the A factors for the X/ClNO reactions are found to increase as the electron affinity of the radical increases, indicating that the tightness of the transition state is directly related to the height of the activation barrier.

Original languageEnglish (US)
Pages (from-to)1022-1029
Number of pages8
JournalJournal of physical chemistry
Volume93
Issue number3
StatePublished - Dec 1 1989

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Electron affinity
electron affinity
reactivity
Activation energy
activation energy
Rate constants
Kinetics
kinetics
Molecules
Fluorescence
resonance fluorescence
Factor X
Helium
energy
Electrons
Ionization potential
electron transfer
Magnetic resonance
tightness
molecules

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

@article{0e33db5b22594acc9233ee554444de0f,
title = "Kinetics and mechanism of X + CINO → XCl + NO (X = Cl, F, Br, OH, O, N) from 220 to 450 K. Correlation of reactivity and activation energy with electron affinity of X",
abstract = "The rate constants for a series of radical reactions with ClNO, X + ClNO → products where X = Cl, F, Br, OH, O, N, have been measured as a function of temperature in discharge flow systems at pressures between 1 and 2 Torr of helium buffer gas. Radicals were detected by resonance fluorescence (X = Cl, Br, OH, O), laser magnetic resonance (X = OH), and chemical conversion/resonance fluorescence (X = F, N). The rate constants, with units of cm3 molecule-1 s-1 and to 95{\%} confidence level, are for Cl + ClNO → Cl2 + NO, [(6.6±1.2) × 10-11]e(128±46)/T; for F + ClNO → FCl + NO, [(1.4 ±0.4) × 10-10]e(-28±84)/T. for Br + ClNO → BrCl + NO, [(1.5±0.2) × 10-11]e(-52±43)/T; for OH + ClNO → ClOH + NO, [(9.0±4.5) × 10-12]e(-1130±170)/T; for OH + ClNO → HONO + Cl, [(9.2±6.5) × 10-14]e(240±130)/T; for O + ClNO → ClO + NO, [(8.3±0.9) × 10-12]e(-1520 ± 36)/T; and for N + ClNO → NCl + NO, [(9.2 ± 2.2) × 10-12]e(-2250±90)/T. Both the reaction activation energies and the logarithms of the room temperature rate constants are found to correlate strongly with the electron affinity of the radical in such a way that high electron affinity leads to enhanced reactivity. The reactivity trend is rationalized by a frontier orbital interaction dominated by the ease with which electron transfer from the ClNO molecule to the X radical can occur to stabilize a polar transition state, a mechanism shown to be widely prevalent in radical-molecule systems. The propensity for this type of interaction is determined by the energy required for electron transfer which, in this case, is given by IPClNO - EAX, where IP refers to ionization potential and EA to electron affinity. In addition, the A factors for the X/ClNO reactions are found to increase as the electron affinity of the radical increases, indicating that the tightness of the transition state is directly related to the height of the activation barrier.",
author = "Abbatt, {J. P.D.} and Toohey, {D. W.} and Fenter, {F. F.} and Stevens, {P. S.} and Brune, {William Henry} and Anderson, {J. G.}",
year = "1989",
month = "12",
day = "1",
language = "English (US)",
volume = "93",
pages = "1022--1029",
journal = "Journal of Physical Chemistry",
issn = "0022-3654",
publisher = "American Chemical Society",
number = "3",

}

Kinetics and mechanism of X + CINO → XCl + NO (X = Cl, F, Br, OH, O, N) from 220 to 450 K. Correlation of reactivity and activation energy with electron affinity of X. / Abbatt, J. P.D.; Toohey, D. W.; Fenter, F. F.; Stevens, P. S.; Brune, William Henry; Anderson, J. G.

In: Journal of physical chemistry, Vol. 93, No. 3, 01.12.1989, p. 1022-1029.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Kinetics and mechanism of X + CINO → XCl + NO (X = Cl, F, Br, OH, O, N) from 220 to 450 K. Correlation of reactivity and activation energy with electron affinity of X

AU - Abbatt, J. P.D.

AU - Toohey, D. W.

AU - Fenter, F. F.

AU - Stevens, P. S.

AU - Brune, William Henry

AU - Anderson, J. G.

PY - 1989/12/1

Y1 - 1989/12/1

N2 - The rate constants for a series of radical reactions with ClNO, X + ClNO → products where X = Cl, F, Br, OH, O, N, have been measured as a function of temperature in discharge flow systems at pressures between 1 and 2 Torr of helium buffer gas. Radicals were detected by resonance fluorescence (X = Cl, Br, OH, O), laser magnetic resonance (X = OH), and chemical conversion/resonance fluorescence (X = F, N). The rate constants, with units of cm3 molecule-1 s-1 and to 95% confidence level, are for Cl + ClNO → Cl2 + NO, [(6.6±1.2) × 10-11]e(128±46)/T; for F + ClNO → FCl + NO, [(1.4 ±0.4) × 10-10]e(-28±84)/T. for Br + ClNO → BrCl + NO, [(1.5±0.2) × 10-11]e(-52±43)/T; for OH + ClNO → ClOH + NO, [(9.0±4.5) × 10-12]e(-1130±170)/T; for OH + ClNO → HONO + Cl, [(9.2±6.5) × 10-14]e(240±130)/T; for O + ClNO → ClO + NO, [(8.3±0.9) × 10-12]e(-1520 ± 36)/T; and for N + ClNO → NCl + NO, [(9.2 ± 2.2) × 10-12]e(-2250±90)/T. Both the reaction activation energies and the logarithms of the room temperature rate constants are found to correlate strongly with the electron affinity of the radical in such a way that high electron affinity leads to enhanced reactivity. The reactivity trend is rationalized by a frontier orbital interaction dominated by the ease with which electron transfer from the ClNO molecule to the X radical can occur to stabilize a polar transition state, a mechanism shown to be widely prevalent in radical-molecule systems. The propensity for this type of interaction is determined by the energy required for electron transfer which, in this case, is given by IPClNO - EAX, where IP refers to ionization potential and EA to electron affinity. In addition, the A factors for the X/ClNO reactions are found to increase as the electron affinity of the radical increases, indicating that the tightness of the transition state is directly related to the height of the activation barrier.

AB - The rate constants for a series of radical reactions with ClNO, X + ClNO → products where X = Cl, F, Br, OH, O, N, have been measured as a function of temperature in discharge flow systems at pressures between 1 and 2 Torr of helium buffer gas. Radicals were detected by resonance fluorescence (X = Cl, Br, OH, O), laser magnetic resonance (X = OH), and chemical conversion/resonance fluorescence (X = F, N). The rate constants, with units of cm3 molecule-1 s-1 and to 95% confidence level, are for Cl + ClNO → Cl2 + NO, [(6.6±1.2) × 10-11]e(128±46)/T; for F + ClNO → FCl + NO, [(1.4 ±0.4) × 10-10]e(-28±84)/T. for Br + ClNO → BrCl + NO, [(1.5±0.2) × 10-11]e(-52±43)/T; for OH + ClNO → ClOH + NO, [(9.0±4.5) × 10-12]e(-1130±170)/T; for OH + ClNO → HONO + Cl, [(9.2±6.5) × 10-14]e(240±130)/T; for O + ClNO → ClO + NO, [(8.3±0.9) × 10-12]e(-1520 ± 36)/T; and for N + ClNO → NCl + NO, [(9.2 ± 2.2) × 10-12]e(-2250±90)/T. Both the reaction activation energies and the logarithms of the room temperature rate constants are found to correlate strongly with the electron affinity of the radical in such a way that high electron affinity leads to enhanced reactivity. The reactivity trend is rationalized by a frontier orbital interaction dominated by the ease with which electron transfer from the ClNO molecule to the X radical can occur to stabilize a polar transition state, a mechanism shown to be widely prevalent in radical-molecule systems. The propensity for this type of interaction is determined by the energy required for electron transfer which, in this case, is given by IPClNO - EAX, where IP refers to ionization potential and EA to electron affinity. In addition, the A factors for the X/ClNO reactions are found to increase as the electron affinity of the radical increases, indicating that the tightness of the transition state is directly related to the height of the activation barrier.

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