Thermal decomposition of CH3I using I-atom absorption

Abstract

The recently developed I-atom atomic resonance absorption spectrometric (ARAS) technique has been used to study the thermal decomposition kinetics of CH3I over the temperature range, 1052-1820 K Measured rate constants for CH3I (+Kr) → CH3 + I (+Kr) between 1052 and 1616 K are best expressed by k (±36%) = 4.36 × 10-9 exp(-19858 K/T) cm3 molecule-1 s-1. Two unimolecular theoretical approaches were used to rationalize the data. The more extensive method, RRKM analysis, indicates that the dissociation rates are effectively second-order, i.e., the magnitude is 61-82% of the low-pressure-limit rate constants over 1052-1616 K and 102-828 torr. With the known E0 = ΔH00 = 55.5 kcal mole-1, the optimized RRKM fit to the ARAS data requires (ΔE)down = 590 cm-1. © 1997 John Wiley and Sons, Inc.