Rate coefficients for the gas-phase reaction of OH radical with α-pinene: an experimental and computational study

Abstract

To cite this article: Manas Ranjan Dash, M. Balaganesh & B. Rajakumar (2014) Rate coefficients for the gas-phase reaction of OH radical with α-pinene: an experimental and computational study,The rate coefficient for the gas-phase reaction of OH radical with α-pinene was measured at 298 K using relative rate methods, with propylene as a reference compound. The ratio of the rate coefficient for the reaction of OH radicals with α-pinene to that of with OH radicals with propylene was measured to be 1.77 ± 0.21. Considering the absolute value of the rate coefficient of the reaction of OH radicals with propylene as (3.01 ± 0.42) × 10 −11 cm 3 molecule −1 s −1 , the rate coefficient for the reaction of OH radicals with α-pinene was determined to be (5.33 ± 0.79) × 10 −11 cm 3 molecule −1 s −1 . To gain a deeper insight into the reaction mechanism, theoretical calculations were also carried out on this reaction. The rate coefficient of OH radical with α-pinene was calculated using canonical variational transition state theory with small-curvature tunnelling. The kinetics data obtained over the temperature range of 200-400 K were used to derive the Arrhenius expression: k(T) = 3.8 × 10 −28 T 5.2 exp[2897/T] cm 3 molecule −1 s −1 . The OH-driven atmospheric lifetime (τ ) and ozone formation potential of α-pinene were calculated and reported in this work.

Experimental and Computational Investigation on the Gas Phase Reaction of Ethyl Formate with Cl Atoms

“…The temperature inside the reaction chamber was calibrated using a K-type thermocouple within the uncertainty of 2 K. Chlorine atoms were generated by photolysis of oxalyl choride ((COCl) 2 ) at 254 nm, using two UV lamps (SANKYO DENKI G8T5, 8 W). false( COCl false) 2 + h υ nobreak0em0.25em⁡ ( ≈ 254 ⁡ nm ) → 2 Cl + 2 CO The typical (COCl) 2 concentration used in the experiments is 6.65 × 10 17 molecules cm –3 , which would lead to the formation of approximately 10 10 –10 11 Cl atoms in the reaction cell. The detailed experimental procedure and set up were described elsewhere in our recently reported articles. , …”

Ozonolysis Chemistry and Phase Behavior of 1-Octen-3-ol-Derived Secondary Organic Aerosol

“…However, the rate constant for OH with other relevant GLVs such as CHA and HXL has been estimated as 6.1 × 10 –11 and 6.3 × 10 –11 cm 3 s –1 molecule –1 , respectively, which is several orders of magnitude higher than ozonolysis (5.8 ± 0.1 × 10 –17 and 5.8 ± 0.9 × 10 –17 cm 3 s –1 molecule –1 for CHA and HXL, respectively), indicating a faster reaction under OH conditions compared to ozonolysis conditions. This is commonly observed with terpenes such as α-pinene as well. , Nonetheless, the reaction with ozone is a significant atmospheric sink for terpenes and this is expected to be the case for OTL as well.…”

“…This is commonly observed with terpenes such as α-pinene as well. 50,51 Nonetheless, the reaction with ozone is a significant atmospheric sink for terpenes 52 and this is expected to be the case for OTL as well.…”

Abstraction and addition kinetics of C2H radicals with CH4, C2H6, C3H8, C2H4, and C3H6: CVT/SCT/ISPE and hybrid meta-DFT methods

“…Whereas, the barrier energies for the abstraction of the hydrogen atom from all molecules are found to be positive at CCSD(T)/cc-pVTZ//M06-2X/ 6-31+G(d,p) and negative at G3(MP2)//M06-2X/6-31+G(d,p) levels of theory. One more parameter that has to be considered to judge the rate of the reaction for any channel is the effective barrier [41][42][43][44][45] Fig. Li et al 22 calculated the barrier for the C 2 H + CH 4 -C 2 H 2 + CH 3 reaction to be in the range of À0.2 to 0.8 kcal mol À1 using the MPW1K, BH&HLYP and B3LYP hybrid density functional theory (DFT) with the 6-31+G(d,p) basis set.…”

“…And also, the product formed due to abstraction of a hydrogen atom from the -CH 2 -group is a secondary radical (CH 3 -CH -CH 3 ), which is more stable than the formation of a primary radical ( CH 2 -CH 2 -CH 3 ) due to abstraction from the CH 3 group of propane. One more parameter that has to be considered to judge the rate of the reaction for any channel is the effective barrier [41][42][43][44][45] (E eff = E TS À E PRC ). Fig.…”