Kinetics and mechanism associated with the reactions of hydroxyl radicals and of chlorine atoms with 1-propanol under near-tropospheric conditions between 273 and 343 K

✍ Scribed by Shahbaz A. Cheema; Kenneth A. Holbrook; Geoffrey A. Oldershaw; Raymond W. Walker

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 292 KB
• Volume: 34
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.10027

✦ Synopsis

Abstract

Rate constants for the reactions of OH radicals and Cl atoms with 1‐propanol (1‐C~3~H~7~OH) have been determined over the temperature range 273–343 K by the use of a relative rate technique. The value of k(Cl + 1‐C~3~H~7~OH) = (1.69 ± 0.19) × 10^−12^ cm^3^ molecule^−1^ s^−1^ at 298 K and shows a small increase of 10% between 273 and 342 K. The value of k(OH + 1‐C~3~H~7~OH) increases by 14% between 273 and 343 K with a value of (5.50 ± 0.55) × 10^−12^ cm^3^ molecule^−1^ s^−1^ at 298 K, and further when combined with a single independent experimentally determined value at 753 K gives k(OH + 1‐C~3~H~7~OH) = 4.69 × 10^−17^T^1.8^ exp(422/T) cm^3^ molecule^−1^ s^−1^, which fits each data point to better than 2%. Two well‐established structure–activity relationships for H abstraction by OH radicals give accurate predictions of the rate constant for OH + 1‐C~3~H~7~OH, provided the β‐CH~2~ group is given an increased reactivity of a factor of about 2 over that for the structurally equivalent CH~2~ group in alkanes at 298 K.

A quantitative product analysis was carried out at 298 K for the Cl‐initiated photooxidation of 1‐C~3~H~7~OH, using both FTIR and gas chromatography. HCHO, CH~3~CHO, and C~2~H~5~CHO were the only major organic primary products observed, although HCOOH was found in much smaller amounts as a secondary product. A key characteristic of the analysis was that the initial values of the product ratio [CH~3~CHO]/[C~2~H~5~CHO] were effectively constant for NO pressures between 0.15 and 0.3 Torr, but fell by about 35% as the pressure fell to 0.0375 Torr. From a detailed consideration of the mechanism for the oxidation, it is suggested that C~2~H~5~CHO, CH~3~CHO (+HCHO), and 3 molecules of HCHO are formed uniquely from CH~3~CH~2~CHOH, CH~3~CHCH~2~OH, and CH~2~CH~2~CH~2~OH radicals, respectively. On this basis, use of the product yields gives the branching ratios of 56, 30, and 14% for Cl atom reaction at the α‐, β‐, and γ‐CH positions in 1‐C~3~H~7~OH at 298 K. Given the very low temperature coefficients involved, little change will occur over tropospheric temperature ranges. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 110–121, 2002