Hydrofluoroolefins (HFOs) are the potential replacements to chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). HFOs are well-known alternates to regular refrigerants and foam expansion agents. The aim of this work is to provide comprehensive description on the environmental acceptability and atmospheric impact of some of these HFOs. In this study, OH-radical initiated photo-degradation of (E)-/(Z)-CHF=CF(CF2)x=1,2CF3 was investigated over the temperature range of 200–400 K using CCSD(T)/aug-cc-pVTZ//M062x/6-31+G(d,p) level of theory. The reaction kinetics was computed using the canonical variational transition state theory (CVT) in conjunction with the small curvature tunneling (SCT) and interpolated single-point energy (ISPE) corrections. A negative temperature-dependent Arrhenius behavior was observed for all the HFO + OH reactions. Various fluorinated aldehydes and acids formed via the interaction of the products with O2 and NOx are also reported as part of this manuscript. Short lifespans and low global warming potentials (GWPs) furthermore characterized the importance of these HFOs as propitious replacements to high GWP CFCs. © 2019 Elsevier B.V.

Balla Rajakumar

Department Of Chemistry

Parth Gupta

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

Journal of Fluorine Chemistry

A theoretical insight on the kinetics for the reaction of (E)-/(Z)-CHF=CF(CF2)x=1,2CF3 with OH radicals under tropospheric conditions

The reactivity of various OVOCs (mainly esters) in the troposphere leads to the generation of various organics, which in turn leads to an increase in the cloud acidity of the Earth's atmosphere. Hence, it becomes necessary to understand the mechanistic aspects of the reaction of these molecules with dominant atmospheric agents. In this study, the tropospheric degradation of one such ester, propyl butanoate (PB; CH3CH2CH2COOCH2CH2CH3) was studied with OH radicals and Cl atoms at the CCSD(T)//M06-2x/6-311+G(2d,2p) and CCSD(T)//BHandHLYP/6-311+G(2d,2p) level of theories over the studied temperature range of 200-400 K. The Arrhenius expressions obtained using the CVT/SCT/ISPE method were calculated as kPB + Cl (200-400 K) = 1.3 × 10-14 T1.3 exp[1335/T] cm3 molecule-1 s-1 and kPB + OH (200-400 K) = 1.8 × 10-26 T4.6 exp[4469/T] cm3 molecule-1 s-1. The obtained kinetics was also well validated against the SAR (structure-activity relationship)-based rate coefficients. The most prominent H-abstraction reaction channels were investigated for the PB + OH/Cl reaction. The abstraction of H atoms attached to the carbon atom present in the β-position to the ester (-C(O)O-) functionality was found to go via the lowest energy activation barriers for the reaction of PB toward both OH radicals and Cl atoms. The product degradation channels were also elucidated in an O2/NOx-rich environment. Moreover, to gauge the impact of the emitted PB on the troposphere, atmospheric lifetimes, radiative efficiencies, global warming potentials, and photochemical ozone creation potentials were also calculated and are included in the manuscript. Copyright © 2019 American Chemical Society.

Journal of Physical Chemistry A

Cl Atoms and OH Radicals Initiated Kinetic and Mechanistic Study on the Degradation of Propyl Butanoate under Tropospheric Conditions

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

Journal	Data powered by TypesetJournal of Fluorine Chemistry
Publisher	Data powered by TypesetElsevier B.V.
ISSN	00221139
Open Access	No