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

Fluorinated hydrocarbon radical-radical reactions in the gas phase have bee n studied at low pressure (0.5 less than or equal to p/mbar less than or eq ual to 2) and low temperature (253 less than or equal to T/K less than or e qual to 333) using the discharge flow reactor molecular beam sampling mass spectrometry (MS) technique. Stable and labile species have been detected b y 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 s elf reaction (2) CHF2 + CHF2 --> products the rate coefficient was measured as k(2) = (1.7 +/- 0.5) . 10(13) exp((-55 5 +/- 89)/T) cm(3)/ mol . s. The stabilisation of C2H2F4* is the main react ion pathway (2a) (k(2a)/k(2) greater than or equal to 0.5), the HF eliminat ion is of minor importance (k(2b)/k(2) = 0.2). No pressure dependence of k(1) and k(2) was observed in the limited pressur e range.