Gas-phase reactivity study of unsaturated nitriles towards OH radicals and Cl atoms at atmospheric pressure

JUAN P. COLOMER, MARÍA B. BLANCO, ALICIA B. PEÑÉÑORY, IAN BARNES, PETER WIESEN AND MARIANO A. TERUEL.

ATMOSPHERIC ENVIRONMENT

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2012 vol. 61 p. 597 - 604

1352-2310

The relative-rate technique has been used to obtain rates coefficients for the reactions of (E)-3-pentenenitrile (CH3CH=CHCHCN) and 4-pentenenitrile (CH2=CHCH2CH2CN) with OH radicals and Cl atoms at 298 K and (760 ± 10) Torr total pressure of synthetic air using different reference compounds. The experiments were performed in an environmental chamber with ?in situ? FTIR spectroscopy to monitor the reactants concentrations. The following room temperature rate coefficients (in cm3 molecule-1 s-1) were obtained: k1 (OH + CH3CH=CHCHCN) = (5.05 ±1.10) × 10-11, k2 (Cl + CH3CH=CHCHCN) = (2.60 ± 0.26) × 10-10 , k3 (OH + CH2=CHCH2CH2CN) = (2.90 ± 0.64) × 10-11 and k4 (Cl + CH2=CHCH2CH2CN) = (2.56 ± 0.26) × 10-10. This is the first kinetic study for all of these reactions. The effect of atom or group substituent on the overall rate coefficients is analyzed and the reactivity of nitriles is compared with those of other unsaturated compounds in the literature. In addition, a comparison between the experimentally determined rate coefficients from this work and the kOH and kCl predicted from k vs EHOMO correlations is presented. The atmospheric lifetimes at room temperature of these compounds has been estimated using the rate coefficients determined in this work.