ORIGINAL PAPER Theoretical study on rate constants for the reactions of CF 3 CH 2 NH 2 (TFEA) with the hydroxyl radical at 298 K and atmospheric pressure Bhupesh Kumar Mishra & Arup Kumar Chakrabartty & Ramesh Chandra Deka Received: 6 November 2012 / Accepted: 7 January 2013 / Published online: 25 January 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract Theoretical investigations are carried out on reac- tion mechanism of the reactions of CF 3 CH 2 NH 2 (TFEA) with the OH radical by means of ab initio and DFT meth- ods. The electronic structure information on the potential energy surface for each reaction is obtained at MPWB1K/6- 31+G(d,p) level and energetic information is further refined by calculating the energy of the species with a Gaussian-2 method, G2(MP2). The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation. Our calculation indicates that the H abstraction from –NH 2 group is the dominant reaction channel because of lower energy barrier. The rate constants of the reaction calculated using canonical transition state theory (CTST) utilizing the ab initio data. The agreement between the theoretical and exper- imental rate constants is good at the measured temperature. From the comparison with CH 3 CH 2 NH 2 , it is shown that the fluorine substution decreases the reactivity of the C-H bond. Keywords Gas phase reactions . G2(MP2) . H abstraction rate constants . IRC calculation . TFEA Introduction Amines are the well-known basic volatile organic com- pounds identified in the atmosphere in both gas and partic- ulate phases [1–4]. Gaseous amines can contribute to the formation of new particle and secondary organic aerosol by either acid–base reactions with gas-phase acids like HNO 3 , H 2 SO 4 etc. [5] or oxidation reactions with atmospheric oxidants such as OH, NO 3 and O 3 [6–9]. Amines have attracted a great deal of attention in recent decades, as some field observations [10] and quantum chemical calculations [11, 12] suggested that secondary organic aerosol generated from amines greatly impacts on climate, visibility and hu- man health [13, 14]. Amines can be emitted directly into the atmosphere by a variety of widespread biogenic and anthro- pogenic sources including automobile exhaust [15], carbon capture and storage [16, 17], animal husbandry [18], aquatic sources [19] and waste incineration and sewage treatment [20]. In the atmosphere, OH, Cl, and NO 3 radicals may react with saturated aliphatic amines via hydrogen ab- straction either from the carbon or the nitrogen position. The hydrogen abstraction will result in the formation of an alkyl or an alkylamino radical species that will promptly react further to produce a wide range of closed shell products like amides, nitrosamides, aldehydes, nitrosamines, nitr- amines in both gas and aqueous phase which may contribute significantly to increase the organic nitrogen fraction of the atmospheric aerosol. Among the degradation prod- ucts of amines, nitrosamines and nitramines have shown potential carcinogenic activity in both gas and aqueous phases. [16, 21]. It is therefore, important to establish the roles of amines degradation product formation mecha- nisms with atmospheric conditions. An understanding of the atmospheric oxidation mechanism of amines has long been cited as the most critical needed for further development of reaction mechanisms for the urban and regional atmosphere. Useful properties of compounds containing amines and their negative impact on environment and human health have motivated many studies on their oxidation process. The dominant atmospheric fate of these species is reaction with the OH radical. Electronic supplementary material The online version of this article (doi:10.1007/s00894-013-1762-7) contains supplementary material, which is available to authorized users. B. K. Mishra : A. K. Chakrabartty : R. C. Deka (*) Department of Chemical Sciences, Tezpur University, Napaam, Tezpur, Assam 784 028, India e-mail: ramesh@tezu.ernet.in J Mol Model (2013) 19:2189–2195 DOI 10.1007/s00894-013-1762-7