Rajakumar Balla

The photo-oxidation of 2,2,2-trifluoroethyl acrylate (TFEA) (CH2CHC(O)OCH2CF3) initiated by OH radicals and Cl atoms was investigated in tropospheric conditions using both experimental and computational methods. The kinetic measurements were carried out in the temperature range of 268-363 K using the relative rate method. The rate coefficients for the reaction of OH radicals with TFEA were measured relative to diethyl ether, ethylene, and acetaldehyde. The rate coefficients for the reaction of Cl atoms with TFEA were measured relative to propylene and ethylene. The rate coefficients for the reaction of TFEA with OH radicals and Cl atoms at 298 K were experimentally measured to be kR1exp - 298 K = (1.41 ± 0.31) × 10-11 cm3 molecule-1 s-1 and kR2exp - 298 K = (2.37 ± 0.50) × 10-10 cm3 molecule-1 s-1, respectively. The deduced temperature-dependent Arrhenius expressions for the reactions of OH radicals and Cl atoms with TFEA are kR1exp - (268 - 363 K) = (9.82 ± 1.37) × 10-12 exp. [(812 ± 152)/T] cm3 molecule-1 s-1 and kR2exp - (268 - 363 K) = (1.25 ± 0.17) × 10-11 exp. [(862 ± 85)/T] cm3 molecule-1 s-1, respectively. To complement our experimental results, computational calculations were performed at CCSD(T)/cc-pVDZ//M062X/6-31+G(d,p) and CCSD(T)/cc-pVDZ//MP2/6-311+G(d,p) levels of theory, respectively, in combination with canonical variational transition-state theory (CVT) with small curvature tunneling (SCT) over the temperature range of 200-400 K. Furthermore, the degradation mechanisms initiated by OH radicals and Cl atoms were proposed for the titled reactions based on the qualitative analysis of the products in gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR). Atmospheric implications, thermochemistry, and branching ratios for the titled reactions are discussed in detail in the paper.

RR-GC-FID technique was used to investigate the rate coefficient (k) for the reaction of vinyl butyrate (VB) with Cl atoms in the temperature range of 268 and 363 K at 760 Torr of N2. The k at 298 K was measured to be k298KVB+Cl=2.57±0.68×10-10 cm3 molecule−1 s−1. To comprehend the reaction pathway, and kinetic parameters associated with the title reaction were assessed computationally using CVT/SCT/ISPE method at CCSD(T)//MP2/6-311++G(d,p) level of theory. Product analysis was performed using GC–MS and GC-IR. Cumulative Atmospheric Lifetime (CAL), Radiative Forcing (RF), Global Warming Potential (GWP) and Photochemical Ozone Creation Potential (POCP) were estimated.

The reactivity of 2-ethoxy ethanol with OH radicals was experimentally measured in the temperature range of 278-363 K using the pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique. The rate coefficient at room temperature was measured to be (1.14 ± 0.03) × 10-11cm3molecule-1s-1, and the Arrhenius expression was derived to bekexpt278-363K= (1.61 ± 0.35) × 10-13exp{(1256 ± 236)/T} cm3molecule-1s-1. Computational calculations were performed to compute the kinetics of the titled reaction in the temperature range of 200-400 K using advanced methods incorporated with tunneling correction at the CCSD(T)/aug-cc-pVTZ//M06-2X/6-31+G(d,p) level of theory. The Arrhenius expression derived from the computationally calculated rate coefficients isktheo200-400K= (1.59 ± 0.35) × 10-13exp{(1389 ± 62)/T} cm3molecule-1s-1. The feasibility of each reaction pathway was also determined using the calculated thermochemical parameters. Atmospheric implication parameters such as cumulative atmospheric lifetime and photochemical ozone creation potential were calculated and are discussed in this paper.

The gas-phase kinetics of the reactions of IO radicals with ethyl formate (EF) and ethyl acetate (EA) were investigated experimentally using cavity ring-down spectroscopy (CRDS). IO radicals were generated in situ in the CRD reaction zone by photolyzing a mixture of (CH3I + O3 + N2) at 248 nm and thereby probed at 445.04 nm. The rate coefficients for the reactions (IO + EF) and (IO + EA) were measured at a total pressure of 65 Torr of N2 in the temperature range of 258-358 and 260-360 K, respectively. The rate coefficients for the reactions (IO + EF) and (IO + EA) were measured experimentally at room temperature to be kExpt,298KIO+EF = (3.38 ± 0.67) × 10-14 and kExpt,298KIO+EA = (1.56 ± 0.30) × 10-13 cm3 molecule-1 s-1, respectively. The effects of pressure and photolysis laser fluence on the kinetics of test reactions were found to be negligible within the experimental uncertainties for the studied range. To complement our experimental findings, the kinetics of the title reactions were investigated theoretically using canonical variational transition state theory (CVT) with small curvature tunnelling (SCT) at the CCSD(T)//M06-2X/def2-SV(P) level of theory in temperatures between 200 and 400 K. Very good agreement was observed between the experimentally measured and theoretically calculated rate coefficients for both the reactions at 298 K. The thermochemical parameters as well as the branching ratios for the title reactions are also discussed in this study. This journal is

Cl atom initiated photo-oxidation of monochlorinated propanes to form the carbonyl compounds was investigated. Propionaldehyde and acetone were identified to be major products in the oxidation of 1-chloropropane and 2-chloropropane, respectively. The complete product analyses were carried out using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR) as analytical tools, and an appropriate oxidation mechanism was proposed on the basis of the product analyses. The temperature dependent rate coefficients for the reactions of Cl atoms with 1-chloropropane (1-CP) and 2-chloropropane (2-CP) were measured experimentally in the gas phase, using the relative rate method in the temperature range 268-363 K and at 1 atm pressure. Ethane, ethylene, and ethyl acetate were used as reference compounds. The obtained rate coefficients for the reactions of Cl atoms with 1-CP and 2-CP at room temperature (298 K) and at 1 atm pressure were (4.64 ± 0.70) × 10 -11 and (2.57 ± 0.44) × 10 -11 cm 3 molecule -1 s -1 , respectively. Furthermore, to complement our experimentally obtained results, computational calculations were performed for these reactions using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) in combination with the CCSD/cc-pVDZ//MP2/6-31+G(d,p) level of theory. Detailed discussion on feasibility of the reactions, branching ratios, degradation mechanism, and atmospheric implications are discussed in this manuscript.

Temperature dependent rate coefficients for the reactions of Cl atoms with cyclohexene and cycloheptene were measured over the 280-360 K temperature range using a relative rate experimental technique with reference to 1,3-butadiene and isoprene. To complement the experimental results, computational calculations were performed in combination with canonical variational transition state theory (CVT) with small curvature tunneling (SCT) and conventional transition state theory (CTST) coupled with Wigner's and Eckart's symmetric and unsymmetric corrections at the MP2/6-31G(d,p) level of theory. The measured rate coefficients for the reactions of Cl atoms with cyclohexene and cycloheptene are kR1298K = (3.26 ± 0.35) × 10-10 cm3 molecule-1 s-1 and kR2298K = (5.68 ± 0.9) × 10-10 cm3 molecule-1 s-1 respectively. The temperature dependent Arrhenius expressions are found to be kR1280-360K = (5.53 ± 1.84) × 10-11exp[(516 ± 104)/T] cm3 molecule-1 s-1 and kR2280-360K = (3.42 ± 2.9) × 10-11exp[(827 ± 268)/T] cm3 molecule-1 s-1 for cyclohexene and cycloheptene respectively. The Cl atom addition reactions are more favorable in the case of cyclohexene, whereas in the case of cycloheptene both addition and abstraction channels are favorable. The rate coefficients for the reactions of cyclohexene and cycloheptene with Cl atoms are compared with the rate coefficients of OH and NO3 radicals, and O3 molecules to know the significance of the Cl atom reactions in the Earth's atmosphere. The cumulative lifetimes, reaction mechanism, feasibility of the reaction and other atmospheric implications of the test molecules were discussed.

Temperature dependent rate coefficients for the gas phase reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one were measured as a function of temperature (298-363 K) and pressure (500-760 Torr; N2 and O2) relative to 1,3-butadiene, isoprene and 1-pentene. Gas Chromatography (GC) coupled with a Flame Ionization Detector (FID) was used to measure the concentrations of the organics. The derived temperature dependent Arrhenius expressions are k1 = (2.82 ± 1.76) × 10-12 exp [(1556 ± 438)/T] cm3 molecule-1 s-1 and k2 = (4.6 ± 2.4) × 10-11 exp [(646 ± 171)/T] cm3 molecule-1 s-1. The corresponding room temperature rate coefficients are (5.55 ± 1.31) × 10-10 cm3 molecule-1 s-1 and (4.14 ± 1.25) × 10-10 cm3 molecule-1 s-1 for the reactions of Cl atoms with 4-hexen-3-one and 5-hexen-2-one respectively. To complement our experimental results, computational calculations were performed for the reactions of Cl atoms with 4-hexen-3-one, 5-hexen-2-one and 3-penten-2-one over the temperature range of 275-400 K using Canonical Variational Transition state theory (CVT) with Small Curvature Tunneling (SCT) in combination with the CCSD(T)/6-31+G(d,p)//MP2/6-311++G(d,p) level of theory. Atmospheric implications, reaction mechanism and feasibility of the title reactions are discussed in this manuscript.

The photo-oxidation reaction of ethyl methacrylate (EMA) initiated by Cl atoms were explored in the Earth's tropospheric conditions using experimental as well as computational methodologies. The experiments were performed to measure the rate coefficients of the title reaction over the temperature range of 268-363 K by the relative rate method. The rate coefficients for the title reaction were measured relative to 1, 3 butadiene and trans-2-butene. The rate coefficient for the title reaction at 298 K was experimentally measured to be kEMA+Cl Exp - 298 K = (2.80 + 0.80) × 10-10 cm3 molecule-1 s-1. The derived Arrhenius expression for the title reaction is kTFEA+Cl Exp - (268-363K)= (2.32 + 0.20) × 10-11 exp [(696 + 54)/T] cm3 molecule-1 s-1. Computational calculations were performed at CCSD(T)//MP2/6-31+G(d, p) level of theory using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) in the temperatures between 200 and 400 K. The degradation mechanism initiated by Cl atoms was proposed for the title reaction based on the qualitative analysis of the products. The important atmospheric parameters such as atmospheric lifetimes, global warming potentials, and photochemical ozone creation potentials, thermochemistry and branching ratios of the test reaction are presented in the manuscript.

The gas-phase kinetics for the reactions of OH radicals and Cl atoms with 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (HF2M2P) were measured at temperatures between 268 and 363 K using the relative rate experimental technique. Methane and acetonitrile were used as reference compounds to measure the rate coefficients of the title reactions. For the reactions of HF2M2P with OH radicals and Cl atoms, the rate coefficients were measured to be (7.07 ± 1.21) × 10-15 and (2.85 ± 0.54) × 10-14 cm3 molecule-1 s-1, respectively, at 298 K. The obtained Arrhenius expressions for the reactions of HF2M2P with OH radicals and Cl atoms are kHF2M2P + OHExp - (268 - 363 K) = (7.84 ± 0.75) × 10-14 exp [-(717 ± 59)/T] and kHF2M2P + ClExp - (268 - 363 K) = (3.21 ± 0.45) × 10-12 exp [-(1395 ± 83)/T] cm3 molecule-1 s-1. In addition to the experimental measurements, computational kinetic calculations were also performed for the title reactions at the M06-2X/MG3S//M06-2X/6-31 + G(d,p) level of theory using advanced methods such as the canonical variational transition-state theory coupled with small curvature tunneling corrections at temperatures between 200 and 400 K. Theoretical calculations reveal that the H-abstraction from the CH3 group is a more favorable reaction channel than that from the OH group. Thermochemistry, branching ratios, cumulative atmospheric lifetime, global warming potential, acidification potential, and photochemical ozone creation potential of HF2M2P were calculated in the present investigation.

The rate coefficients for the reaction of CH3CF = CF2 with OH radicals were calculated using CCSD(T)/cc-pVTZ//M06-2X/6-31G(d,p) level of theory over the temperature range of 200–400 K. Canonical Variation Transition state theory (CVT) in combination with Small Curvature Tunneling (SCT) was employed to calculate the rate coefficients for the title reaction. The temperature dependent rate coefficient for the reaction of OH radicals with CH3CF = CF2 was calculated to be (5.77 ± 2.55) × 10−25 T3.76 exp [(2355 ± 37)/T] cm3 molecule−1 s−1. Thermodynamic parameters, branching ratios and atmospheric implications of the title reaction were also computed and discussed in the article.