The predominant tautomeric forms of N1-H, N2-H of 5-(2,6-dimethyl-and 5-(2,6-diisopropylphenoxy)-(1H)-tetrazoles were analyzed at B3LYP method using 6-311G(d,p) basis set in the gas phase. The N1-H form of tetrazoles was found to be more stable than N2-H form in both solid and gas phases. Crystal structures of both tetrazoles show an intermolecular Hbond between N1-H and N4 atom of other tetrazole space. The hydrogen bonds between each tautomer of tetrazoles were evaluated at B3LYP/6-311G(d,p) level. The geometrical parameters and spectral data of tetrazoles and their variation were studied in both solid and gas phases.

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The decomposition processes and reactivity of C4F90CH2O• radical formed from C4F90CH3 (HFE-7100) have been studied by density function theory computational methods. All calculations were performed at B3LYP and mPW1PW91 levels of theory with the 6-311G(d,p) basis set. The calculated barrier heights were further improved by QCISD(T)/6-31G(d)//MP2/6-31G(d) methodology to obtain better rate constants. Five possible pathways were investigated: reaction with O2, reaction with OH radical, C-O bond dissociation, release of H radical and finally rearrangement of the radical and then C-O bond cleavage with energy barriers of 6.35 (6.09) [12.12], 12.85 (16.87) [7.51], 17.05 (21.77) [28.34], 20.3 (20.75) [18.13], 32.60 (31.50) [32.63] and 16.07 (18.73) [20.04] kcal mol−1, respectively (the values in the parentheses for mPW1PW91 and in the brackets for the QCISD(T) method). Rate constants were calculated by utilising canonical transition state theory in the temperature range of 200–400 K and 1 atm pressure, and Arrhenius diagrams were plotted. The results showed that H elimination and H abstraction pathways are dominant for degradation of C4F90CH2O• radical in the atmosphere. A smooth transition from the reactants to products on the corresponding potential energy surface was confirmed by intrinsic reaction coordinate calculations.

The mechanism of decomposition and reactivity of C4F9OC2H4O• radical obtained from C4F9OC2H5 (HFE-7200) was studied by a computational method. All calculations were performed at the B3LYP and mPW1PW91 levels of theory with a 6-311G(d,p) basis set. Four possible pathways were investigated: (i) reaction with atmospheric O2, (ii) reaction with atmospheric OH radical, (iii) release of H radical and (iv) rearrangement of the radical in two steps and then C–O bond cleavage. These pathways (1), (2), (3), (4a), (4b) and (4c) for the four steps listed, respectively, had energy barriers equal to 6.9, 11.9, 17.7, 30.8, 11.0 and 9.9 kcal mol–1, respectively. Canonical transition state theory was used to calculate rate constants for all steps in the range of 200–400 K and Arrhenius diagrams were plotted for them. The results showed that reaction with atmospheric O2 with a rate constant equal to 48.97 cm3 mol–1 s–1 is the dominant pathway for degradation of C4F9OC2H4O• radical in the atmosphere.

This investigation involves the ab initio quantum mechanical study of the decomposition and reactivity of the CHF2CF2CF2OCH2O• radical that is formed from CHF2CF2CF2OCH3 (HFE-356pcc3). The geometries of the reactants, products and transition states were optimised at the B3LYP and B3PW91 levels of theory using the 6-311G(d,p) basis set. Five important pathways for the decomposition and reactivity of CHF2CF2CF2OCH2O• were investigated: (1) reaction with atmospheric O2, (2) reaction with atmospheric •OH radical, (3) C–O bond cleavage, (4) H elimination and (5) the migration of hydrogen from carbon to oxygen and then C–O bond cleavage, with energy barriers of 4.4 (5.0), 11.9 (12.4), 17.0 (17.3), 20.4 (19.4) and 32.2 (32.6) and 15.5 (16.7) kcal mol−1 respectively [values in parentheses are for the B3PW91/6-311G(d,p) level of theory]. Rate constants were calculated by utilising canonical transition state theory in the range 200–400 K and the corresponding Arrhenius diagrams have been plotted. The results showed that the rates of decomposition and reaction increase with increasing temperature. Also, between 200 and 306 K, path (1) has the highest rate constant: moreover, it was concluded that reaction with atmospheric O2 is the dominant pathway for the consumption of CHF2CF2CF2OCH2O• in the atmosphere. An intrinsic reaction coordinate calculation was performed to confirm the existence of a transition state on the corresponding potential energy surface.