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

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. REACTIONS OF HYDROXYL RADICALS AND CHLORINE ATOMS WITH 1-PROPANOL 111A 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.

Rate constant and products for the reaction of Cl atom with n‐butyraldehyde

“…The NO is rapidly decreased after the initiation of the reaction and NO 2 is formed, so the main fate of the acylperoxy radicals will be the formation of corresponding stable acyl peroxynitrate and not lower aldehyde [17,25]. Regarding the increase in product yields of CH 3 CHO and CO, a similar trend for acetaldehyde was reported by Cheema and coworkers [26] when they studied the mechanisms of Cl atom reaction with propanol. In this work, the reason might be that the degradation of alkylperoxy radicals to alkoxy radicals is the key process for both formation of CH 3 CHO and CO.…”

Relative rate constants for the reactions of hydroxyl radicals and chlorine atoms with a series of aliphatic alcohols

“…On the basis of the kinetics and mechanisms of the reaction of Cl atoms with n ‐propane and n ‐butane measured by Tyndall et al 25, average values of 7.6 × 10 −11 and 3.1 × 10 −11 cm 3 molecule −1 s −1 can be derived for the Cl attack at per‐CH 2 and per‐CH 3 group in alkanes. Cheema et al 26 have carried out a quantitative analysis for the reaction of Cl atoms with n ‐propyl alcohol, and they estimated values of 8.7 × 10 −11 , 4.7 × 10 −11 , and 2.2 × 10 −11 cm 3 molecule −1 s −1 for the Cl attack at α‐CH 2 , β‐CH 2 , and γ‐CH 3 group, respectively. The activities of β‐CH 2 and γ‐CH 3 groups in n ‐C 3 H 7 OH towards Cl atom attack are clearly lower compared with the CH 2 and CH 3 groups in alkanes.…”

Facial emotion recognition and alexithymia in adults with somatoform disorders

“…Numerous studies have reported the rate coefficients for the reactions of n ‐propanol and iso ‐propanol with OH in the gas phase 5–15. Even though the reported values of k 1 (298 K) agree well with each other, the values of k 1 below 298 K are uncertain.…”

“…Even though the reported values of k 1 (298 K) agree well with each other, the values of k 1 below 298 K are uncertain. There are two measurements of k 1 below 298 K, one an absolute determination 13 and the other a relative rate study 14; they disagree with each other. There is good agreement among the reported values of k 2 (298 K) 7–13,15.…”