KINETICS OF IODINATION OF HYDROGEN-SULFIDE BY IODINE AND THE HEAT OF FORMATION OF THE SH RADICAL

The kinetics of the gas‐phase thermal iodination of hydrogen sulfide by I2 to yield HSI and HI has been investigated in the temperature range 555–595 K. The reaction was found to proceed through an I atom and radical chain mechanism. Analysis of the kinetic data yields log k (l/mol·sec) = (11.1 ± 0.18) – (20.5 ± 0.44)/θ, where θ = 2.303 RT, in kcal/mol. Combining this result with the assumption E−1 = 1 ± 1 kcal/mol and known values for the heat of formation of H2S, I2, and HI, ΔHf,2980(SH) = 33.6 ± 1.1 kcal/mol is obtained. Then one can calculate the dissociation energy of the HSH bond as 90.5 ± 1.1 kcal/mol with the well‐known values for ΔHf,2980 of H and H2S. Copyright © 1979 John Wiley & Sons, Inc.