Shock Wave and Theoretical Modeling Study of the Dissociation of CH2F2. II. Secondary Reactions.

The thermal dissociation of CH2F2 and the reaction of CF2 with H2 was studied in shock waves over the temperature range 1800-2200 K, monitoring the absorption-time profiles at 248 nm. Besides contributions from CF2, the signals showed strong absorptions from secondary reaction products, probably mostly CH2F formed by the reaction CHF + H2 → CH2F + H. Rate constants of a series of possible secondary reactions were modeled, including falloff curves for the thermal dissociations of CHF, CHF2, and CH2F and rate constants of the reactions CHF + CH2F2 → CHF2 + CH2F, CHF + H2 → CH2F + H, H + CH2F2 → CHF2 + H2, H + CF2 → CF + HF, and H + CF → C + HF. On this basis, concentration-time profiles were simulated and compared with experimental absorption-time profiles.