Rate coefficient for the reaction of β-pinene with OH radicals was determined at 298K and 800Torr of N2 using the relative rate technique. Isobutylene was used as a reference compound and the concentrations of the organics were followed by gas chromatographic analysis. The rate coefficient for the reaction of β-pinene with OH radical was measured to be (9.35±2.79)×10-11cm3 molecule-1s-1. Theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small-curvature tunneling (SCT). The kinetics data obtained over the temperature range of 200-400K were used to derive the Arrhenius expression: k(T)=8.24×10-23T3.41 exp[2421/T]cm3molecule-1s-1. The OH-driven atmospheric lifetime (τ) and global warming potential (GWP) for β-pinene were computed and concluded that β-pinene is very short lived (2.5h) in the Earth's atmosphere with a GWP of 1.6×10-2 at 20 years horizon of time and which is negligible. The ozone formation potential of β-pinene was also calculated and reported in this present work. © 2013 Elsevier Ltd.

Balla Rajakumar

Department Of Chemistry

ATMOSPHERIC LIFETIME

GLOBAL WARMING POTENTIAL

OH radical

OZONE FORMATION POTENTIALS

Rate coefficients

Free radicals

Global warming

Molecules

Ozone

Monoterpenes

beta pinene

Hydroxyl radical

isobutylene

atmospheric pollution

Curvature

experimental study

gas chromatography

GAS PHASE REACTION

nitrogen

Reaction kinetics

theoretical study

article

chromatography

Energy transfer

Greenhouse effect

Kinetics

priority journal

Temperature

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Atmospheric Environment

A dual-level direct dynamic method is employed to estimate the addition and hydrogen abstraction rate coefficients for the reactions of cis-CHF=CHCHF2, trans-CHF=CHCHF2, CF2=CHCHF2 and CF2=C=CHF with hydroxyl radicals (OH) using variational transition state theory (VTST) with interpolated single-point energies (ISPE) at CCSD(T)/cc-pVTZ//M06-2X/6-31+G(d,p) level of theory. The rate coefficients of cis-CHF=CHCHF2, trans-CHF=CHCHF2, CF2=CHCHF2 and CF2=C=CHF + OH reactions were computed using Canonical Variational Transition state Theory (CVT) with Small Curvature Tunneling (SCT) in the temperature range of 200-400 K. It was found that the contribution of abstraction reactions toward the overall reaction to be insignificant, and hence negligible in comparison to the addition reactions in the studied temperature range of 200-400 K. The total rate coefficient for cis-CHF=CHCHF2, trans-CHF=CHCHF2, CF2=CHCHF2 and CF2=C=CHF + OH reactions were calculated to be 6.83 × 10-13, 3.17 × 10-12, 5.43 × 10-13 and 2.22 × 10-13 cm3 molecule-1 s-1, respectively at 298 K. The atmospheric life times of cis-CHF=CHCHF2, trans-CHF=CHCHF2CHF, CF2=CHCHF2 and CF2=C=CHF are estimated to be 16, 3.4, 21 and 57 days respectively at 277 K. The global warming potentials (GWPs) of title molecules at the time horizons of 20, 100 and 500 years were computed using the rate coefficients and radiative forcing values obtained in this study. Since these title molecules show significantly lower GWPs than many hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), it is conclude that these hydrofluoro-olefines (HFOs) may be possible replacements to HFCs in many industrial applications. © 2015 Elsevier B.V. All rights reserved.

Journal of Fluorine Chemistry

Kinetic parameters for the reaction of OH radical with cis-CHF=CHCHF2, trans-CHF=CHCHF2, CF2=CHCHF2 and CF2=C=CHF: Hybrid meta DFT and CVT/SCT/ISPE calculations

The rate coefficients of hydroxyl radical (OH) reaction with limonene were computed using canonical variational transition state theory with small-curvature tunnelling between 275 and 400 K. The geometries and frequencies of all the stationary points are calculated using hybrid density functional theory methods M06-2X and MPWB1K with 6-31+G(d,p), 6-311++G(d,p), and 6-311+G(2df,2p) basis sets. Both addition and abstraction channels of the title reaction were explored. The rate coefficients obtained over the temperature range of 275-400 K were used to derive the Arrhenius expressions: k(T) = 4.06×10-34 T7.07 exp[4515/T] and k(T) = 7.37×10-25 T3.9 exp[3169/T] cm3 molecule-1 s-1 at M06-2X/6-311+G(2df,2p) and MPWB1K/6-311+G(2df,2p) levels of theory, respectively. Kinetic study indicated that addition reactions are major contributors to the total reaction in the studied temperature range. The atmospheric lifetime (τ) of limonene due to its reactions with various tropospheric oxidants was calculated and concluded that limonene is lost in the atmosphere within a few hours after it is released. The ozone production potential of limonene was computed to be (14-18) ppm, which indicated that degradation of limonene would lead to a significant amount of ozone production in the troposphere. © 2015 Taylor & Francis.

Molecular Physics

Theoretical investigations of the gas phase reaction of limonene (C10H16) with OH radical

The rate coefficient for the gas-phase reaction of Cl atoms with pcymene was determined as a function of temperature (288-350 K) and pressure (700-800 Torr) using the relative rate technique, with 1,3-butadiene and ethylene as reference compounds. Cl atoms were generated by UV photolysis of oxalyl chloride ((COCl)2) at 254 nm, and nitrogen was used as the diluent gas. The rate coefficient for the reaction of Cl atoms with p-cymene at 298 K was measured to be (2.58 ± 1.55) × 10-10 cm3 molecule-1 s-1. The kinetic data obtained over the temperature range 288-350 K were used to derive an Arrhenius expression: k(T) = (9.36 ± 2.90) × 10-10 exp[-(488 ± 98)/T] cm3 molecule-1 s-1. Theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) between 250 and 400 K. The calculated rate coefficients obtained over the temperature range 250-400 K were used to derive an Arrhenius expression: k(T) = 5.41 × 10-13 exp[1837/T] cm3 molecule-1 s-1. Theoretical study indicated that addition channels contribute maximum to the total reaction and H-abstraction channels can be neglected. The atmospheric lifetime (τ) of p-cymene due to its reactions with various tropospheric oxidants was estimated, and it was concluded that the reactions of p-cymene with Cl atoms may compete with OH radicals in the marine boundary layer and in coastal urban areas where the concentration of Cl atoms is high. (Chemical Equation Presented). © 2014 American Chemical Society.

Journal of Physical Chemistry A

Experimental and computational investigation on the gas phase reaction of p-cymene with Cl atoms

The gas phase temperature dependent rate coefficients of Cl atoms with 2,2,2-trifluoroethylbutyrate, CH<inf>3</inf>CH<inf>2</inf>CH<inf>2</inf>C(O)OCH<inf>2</inf>CF<inf>3</inf>, were measured in the temperature range 268-343 K, at atmospheric pressures using the relative rate method, with ethyl acetate and ethane as reference compounds. The temperature dependent rate coefficients for the reaction of 2,2,2-TFEB + Cl were measured and were used to deduce the Arrhenius expression: k<inf>268-343K</inf> = [(4.42 ± 0.01) × 10-19]T2.6 exp{(1132 ± 566)/T} cm3 molecule-1 s-1. At 298 K, the rate coefficient for the title reaction is (4.54 ± 2.87) × 10-11 cm3 molecule-1 s-1, which is in good agreement with a previously reported value at 298 K. To complement our experimental results over the studied temperature range, theoretical kinetic calculations were also performed for the title reaction using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) corrections in combination with the CCSD(T)/cc-pVDZ//M062X/6-31+g(d,p) level of theory. The temperature dependent Arrhenius expression was obtained to be k(T) = (1.89 ± 2.64) × 10-21T3.4 exp{(1321 ± 111)/T} cm3 molecule-1 s-1. The branching ratios, atmospheric implications, and degradation mechanism of 2,2,2-trifluoroethylbutyrate, CH<inf>3</inf>CH<inf>2</inf>CH<inf>2</inf>C(O)OCH<inf>2</inf>CF<inf>3</inf>, were discussed in detail in this manuscript. (Graph Presented). © 2015 American Chemical Society.

Gas Phase Kinetics of 2,2,2-Trifluoroethylbutyrate with the Cl Atom: An Experimental and Theoretical Study

Rate coefficients for the reactions of C2H radicals with methane (k1), ethane (k2), propane (k3), ethylene (k4), and propylene (k5) were computed using canonical variational transition state theory (CVT) coupled with hybrid-meta density functional theory (DFT) over a wide range of temperatures from 150 to 5000 K. The quantum chemical tunneling effect was corrected by the small curvature tunneling (SCT) method. The dynamic calculations are performed using the variational transition state theory (VTST) with the interpolated single-point energies (ISPE) method at the CCSD(T)/cc-pVTZ//M06-2X/6-31+G(d,p) level of theory. Intrinsic reaction coordinate (IRC) calculations were performed to verify that the transition states are connected to the reactants and products. The rate coefficients obtained over the studied temperature range yield the following Arrhenius expressions (cm3 molecule-1 s-1): k1 = 4.69 × 10-19T2.44 exp[331/T], k2 = 4.29 × 10-17T2.11 exp[432/T], k3 = 4.81 × 10-17T1.98 exp[697/T], k4 = 7.54 × 10-21T2.96 exp[1942/T], and k5 = 8.04 × 10-23T3.44 exp[3011/T] cm3 molecule-1 s-1. Branching ratio calculation for the reactions of C2H radicals with ethylene and propylene shows that the abstraction reactions are not important at lower temperatures. However, as the temperature increases, abstraction reactions become more important. © the Owner Societies 2015.

Physical Chemistry Chemical Physics

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

The kinetics and abstraction rate coefficients of hydroxyl radical (OH) reaction with pinonaldehyde were computed using G3(MP2) theory and transition-state theory (TST) between 200 and 400 K. Structures of the reactants, reaction complexes (RCs), product complexes (PCs), transition states (TSs), and products were optimized at the MP2(FULL)/6-31G* level of theory. Fifteen transition states were identified for the title reaction and confirmed by intrinsic reaction coordinate (IRC) calculations. The contributions of all the individual hydrogens in the substrate molecule to the total reaction are computed. The quantum mechanical tunneling effect was computed using Wigner's and Eckart's methods (both symmetrical and unsymmetrical methods). The reaction exhibits a negative temperature dependent rate coefficient, k(T) = (1.97 ± 0.34) × 10 -13 exp[(1587 ± 48)/T] cm 3 molecule -1 s -1, k(T) = (3.02 ± 0.56) × 10 -13 exp[(1534 ± 52/T] cm 3 molecule -1 s -1, and k(T) = (4.71 ± 1.85) × 10 -14 exp[(2042 ± 110)/T] cm 3 molecule -1 s -1 with Wigner's, Eckart's symmetrical, and Eckart's unsymmetrical tunneling corrections, respectively. Theoretically calculated rate coefficients are found to be in good agreement with the experimentally measured ones and other theoretical results. It is shown that hydrogen abstraction from -CHO position is the major channel, whereas H-abstraction from -COCH 3 is negligible. The atmospheric lifetime of pinonaldehyde is computed to be few hours and found to be in excellent agreement with the experimentally estimated ones. © 2012 American Chemical Society.

Abstraction kinetics of H-atom by OH radical from pinonaldehyde (C 10H 16O 2): Ab initio and transition-state theory calculations

The rate coefficients of ((E)-CF 3CH=CHF, (Z)-CF 3CH=CHF, (E)-CF 3CF=CHF, and (Z)-CF 3CF=CHF) + OH reactions were computed using M06-2X/6-31+G(d,p) theory in the temperature range of 200 and 400 K. The possible reaction mechanisms of the ((E)-CF 3CH=CHF, (Z)-CF 3CH=CHF, (E)-CF 3CF=CHF, and (Z)-CF 3CF=CHF) + OH reactions were examined. The rate coefficients for the addition and abstraction reactions were calculated using canonical variational transition state theory (CVT) and conventional transition state theory (CTST), respectively, and we concluded that abstraction reactions are negligible within the temperature range and addition reactions take the lead role. The small curvature tunnelling (SCT) was included in the computation of the rate coefficients. The temperature dependent rate expressions (in cm 3 molecule -1 s -1) of the (E)-CF 3CH=CHF, (Z)-CF 3CH=CHF, (E)-CF 3CF=CHF, and (Z)-CF 3CF=CHF + OH reactions between 200 and 400 K are presented. The atmospheric lifetimes and global warming potentials (GWPs) of the test molecules were computed using the rate coefficients obtained in this study, and it is concluded that these molecules are very short-lived in the Earth's atmosphere with low GWPs. © 2012 American Chemical Society.

Rate coefficients and reaction mechanism for the reaction of OH radicals with (E)-CF 3CH=CHF, (Z)-CF 3CH=CHF, (E)-CF 3CF=CHF, and (Z)-CF 3CF=CHF between 200 and 400 K: Hybrid density functional theory and canonical variational transition state theory calculations

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Vibrational analysis of 4-chloro-3-nitrobenzonitrile by quantum chemical calculations

Biogeosciences

Emissions of BVOC from lodgepole pine in response to mountain pine beetle attack in high and low mortality forest stands

The Journal of Physical Chemistry A

Photochemical Aging of α-Pinene Secondary Organic Aerosol: Effects of OH Radical Sources and Photolysis

Experimental and theoretical rate coefficients for the gas phase reaction of β-Pinene with OH radical

Journal	Atmospheric Environment
ISSN	13522310
Open Access	No