HF/HCL VIBRATIONAL AND ROTATIONAL DISTRIBUTIONS FROM 3-CENTERED AND 4-CENTERED UNIMOLECULAR ELIMINATION-REACTIONS

The infrared chemiluminescence from the HF elimination reactions of CF3H, CF3CH3, C2H5F, C2F5H, n-C3F7H, and i-C3F7H has been used to assign the vibrational and rotational distributions of HF. The chemically activated fluoroalkane molecules were formed by H atom recombination with the appropriate fluoroalkyl radicals, which were generated by reactions of H atoms with the fluoroalkyl iodide precursor molecules. The HF vibrational distributions decline monotonically with increasing energy. The mean HF vibrational energy is larger than the statistical expectation, and 25-35% of the potential energy of the exit channel is specifically released as HF vibrational energy. The HF(upsilon) rotational excitation is modest, and < E(R)(HF) > seems to be equal to or less than the statistical expectation. The HF(upsilon,J) distributions are used to discuss the dynamics of these HF elimination reactions. The energy disposal pattern from the HF elimination reaction from CF3H is compared to the vibrational energy distributions of HCl from the CF2HCl, CFH2Cl, and CFHCl2 molecules that were generated by secondary reactions in the F + CFH2Cl, CH3Cl, and CH2Cl2 systems. In general, three-centered reactions of halomethanes release a larger fraction of the potential energy as < E(V)(HX) > than do four-centered reactions of haloethanes.