Kinetics of the Gas-Phase Reaction of Some Unsaturated Alcohols with the Nitrate Radical

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2002-02, Vol.106 (6), p.945-951
• Main Authors: Noda, Jun, Nyman, Gunnar, Langer, Sarka
• Format: Article
• Language: English
• ISSN: 1089-5639; 1520-5215; 1520-5215
• DOI: 10.1021/jp012329s

Rate coefficients for the gas-phase reaction between nitrate radicals and the unsaturated alcohols 2-buten-1-ol (crotyl alcohol, a mixture of cis and trans), 3-methyl-2-buten-1-ol (MBO321), and 3-methyl-3-buten-1-ol (MBO331) and the alkenes 2-methyl-1-butene and 3-methyl-1-butene have been determined. The values that are found are (4.1 ± 0.4) × 10-13, (1.0 ± 0.1) × 10-12, (2.7 ± 0.2) × 10-13, (5 ± 1) × 10-13, and (1.4 ± 0.2) × 10-14 cm3 molecule-1 s-1, respectively. In addition, the rate coefficients for 2-propen-1-ol (allyl alcohol), 3-buten-2-ol, 2-methyl-3-buten-2-ol (MBO232), and 2-methyl-2-butene were redetermined. The experiments were performed using the relative rate technique. One set of experiments was carried out using a glass reactor and long-path FTIR spectroscopy. A second set of experiments was carried out with a collapsible sampling bag as the reaction chamber, employing solid-phase micro extraction (SPME) for sampling and gas chromatography/flame ionization detection for analysis of the reaction mixtures. The results from the two experimental methods showed good correspondence. All experiments were carried out at 297 ± 2 K and 1020 ± 10 mbar and using both synthetic air and nitrogen as the bath gas. The energy of the highest occupied molecular orbital (E HOMO) of the investigated organic compounds was calculated using the PM3 semiempirical approach, and a relation to ln(k) was observed. A similar relation, available from the literature developed for alkenes, would underestimate the unsaturated alcohol rate coefficients slightly. The measured values of the rate coefficients for the unsaturated alcohols are in reasonable agreement with those predicted by a structure−activity relationship (SAR) available in the literature. However, the SAR slightly overestimates the rate coefficients. The presence of the OH group in the examined alcohols does not affect the NO3 rate coefficient compared to that of the parent alkene, except in the case of MBO321 and MBO331 where steric effects may be responsible for lowering the reactivity.