Gas-phase kinetics of the self reactions of the radicals CH2F and CHF2

Fluorinated hydrocarbon radical-radical reactions in the gas phase have been studied at low pressure (0.5 less than or equal to p/mbar less than or equal to 2) and low temperature (253 less than or equal to T/K less than or equal to 333) using the discharge flow reactor molecular beam sampling mass spectrometry (MS) technique. Stable and labile species have been detected by MS applying low energy electron impact as well as multiphoton ionisation. For the combination reaction (1) CH2F + CH2F --> products the rate coefficient k(1) = (7.0 +/- 0.8) . 10(12) (T/298)((-3.9+/-1.0)) cm(3)/mol . s was determined. At low pressure the HF elimination pathway (1b) (1b) CH2F + CH2F --> C2H3F + HF is the main channel (k(1b)/k(1) = (0.82 +/- 0.015)). For the CHF, radical self reaction (2) CHF2 + CHF2 --> products the rate coefficient was measured as k(2) = (1.7 +/- 0.5) . 10(13) exp((-555 +/- 89)/T) cm(3)/ mol . s. The stabilisation of C2H2F4 is the main reaction pathway (2a) (k(2a)/k(2) greater than or equal to 0.5), the HF elimination is of minor importance (k(2b)/k(2) = 0.2). No pressure dependence of k(1) and k(2) was observed in the limited pressure range.