Kinetics of Coordinate Bond Formation. III. Method of Temperature Patterns and the Reaction NH₃+BF₃

The method for determining rate constants from the temperature pattern in dilute spherical diffusion flames is critically examined, and several possible sources of error are corrected for. The method is tested by a re-examination of the reaction NH3+BF3 over a wide range of experimental parameters. On the whole, previous results are confirmed, but the high-pressure limiting rate is found to be 1.2×1011 cm3/mole-sec, somewhat less than half of the former value, and some new quantities can be measured. Ammonia is found to be about 3 times as effective as nitrogen in energy-exchange collisions with the excited product of the initial addition reaction. In the absence of N2, the rate constant is ½ the high-pressure limit when the NH3 concentration is about 8×10—8 mole/cm3. The heat of the gas-phase addition reaction is 27.5±2 kcal/mole and the equilibrium constant for the reverse reaction is ≪2×10—10 mole/cm3. The activation energy, if any, is less than 3 kcal/mole.