Atmospheric chemistry of HFE-7000 (i-C₃F₇OCH₃) and isofluoro-propyl formate (i-C₃F₇OC(O)H): reactions with OH radicals, atmospheric lifetime and fate of alkoxy radical (i-C₃F₇OCH₂O^•) – a DFT study

ABSTRACT

The mechanism of hydrogen abstraction reaction between HFE-7000 (i-C₃F₇OCH₃) and OH radicals using M06-2X functional in conjunction with 6-31+G(d,p) basis set is investigated. The pre-reactive and post-reactive complexes from intrinsic reaction coordinate calculations are validated at entrance and exit channels, respectively. The standard enthalpies of formation for the species and bond dissociation energy for C–H bond are also estimated. The rate constants of the titled reactions over the temperature range of 250–450 K are reported. The OH-driven atmospheric life time of i-HFE-7000 is computed to be 3.19 years. The atmospheric fate of the alkoxy radical (i-C₃F₇OCH₂O^•) is also explored here for the first time. Three prominent plausible decomposition channels including oxidation are considered in detail. The thermochemical data reveal that reaction with O₂ is the dominant path for the decomposition of i-C₃F₇OCH₂O^• radical. Moreover, rate constant for the OH-initiated hydrogen abstraction of isofluoro-propyl formate (i-C₃F₇OC(O)H) is also reported.

Graphical Abstract

KEYWORDS:

• Segregated HFE
• M06-2X
• isodesmic reactions
• atmospheric lifetime
• alkoxy radical

Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/00268976.2015.1108471.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Department of Science and Technology, New Delhi [SR/NM/NS-1023/2011-G]; CSIR, New Delhi [09/796(0038)/2012-EMR-1]; University Grants Commission, New Delhi [No. F.4-2/2006(BSR)/CH/14-15/0217].