The homogeneous gas-phase reaction H+p-H2=o-H2+H has been studied in the temperature range 300° to 444°K. Within this range the results fitted the equation log10k1 = 15.454 − 3.490×103/T+3.836×105/T2 cm3 mole−1 sec−1. The results were interpreted in terms of activated-complex theory with quantum-mechanical tunneling. From the information about the tunneling factors provided by the curvature of the Arrhenius plot it was possible to calculate the imaginary frequency of the asymmetric vibration of the complex corresponding to its coordinate of decomposition on the assumption of a truncated parabolic barrier. The value obtained was 1213i cm−1. For the same model ΔE0° was found to be 9.7 kcal mole−1. The almost exponential dependence of the tunneling factor on 1/T for Eckart barriers made it impossible to interpret the curvature in terms of such a barrier except for considerably larger values of barrier height and/or imaginary frequency than have been found in recent theoretical calculations.

The reaction D+H2=HD+H has been studied in the gas phase in the temperature range 274° to 468°K. By attributing the curvature in the Arrhenius plot to quantum-mechanical tunneling and interpreting the results in terms of absolute reaction rate theory the rate constant was given by the expression k3=3.63×1015T−12Γexp(−9.40×103/RT). The results obtained previously for the reaction H+p-H2=o-H2+H fitted the equation k1=1.18×1015T−12Γ exp(−9.21×103/RT). The tunneling factors Γ were calculated on the assumption of a truncated parabolic barrier and gave almost identical values for the force constant of the asymmetric stretching vibration of the complex. The results are compared with recent theoretical calculations.

The authors have measured the rate constant for the reaction H + D2 = HD + D ill the temperature range 368468" I<. This was found to be given by the relation: k., = 4.37 X lo1? exp (-7.30 X 103/RT) cm3 ~llole-~s-l.

The sallle compound was also prepared by substituting ammonium hyclroside (12 N, 2 ml) for ammonium formate. However, the yield in this case was lower (0.3 g). Xo depression of melting point \\.as observed on a 111ised melting point determination and the infrared spectra were superimposable.1. P. SIYGH and J. L. BOIVIN. Can. J. Cheru. 40, 935 (1962).