The kinetics and thermochemistry of S2F10 pyrolysis

Data on the kinetics of S₂F₁₀ pyrolysis, which gives SF₄ + SF₆, have been reinterpreted to give a value for the equilibrium constant of S₂F₁₀ ? SF₄ + SF₆. This, together with statistical estimates of the entropy and heat capacity of S₂F₁₀, can be used to give for this reaction values of ΔH = 19.7 ± 1.0 kcal/mole and ΔS = 47.6 ± 2 gibbs/mole. ΔH(S₂F₁₀) = –494 kcal/mole. A compatible mechanism is shown to be S₂F₁₀ ? 2SF₅ (fast); 2SF₅ ? SF₆ + SF₄ (slow) with step 2 rate-determining. The overall, best first order rate constant is proposed as k_meas = 10^{17.42–43.0/θ} sec^?1 = K₁k₂, where θ = 2.303RT in kcal/mole. Independent measurements of δH and S° for the SF₅ radical, permits the evaluation of the equilibrium constant K₁ = 10^{8.92–(27.1 ± 6)/θ} l./mole-sec and yields k₂ = 10^{8.50–15.9/θ} l./mole-sec. The observed homogeneous catalysis by NO and CHCl ? CHCl can be explained in terms of a direct abstraction of F from S₂F₁₀ : C + S₂F₁₀ → CF + S₂F₉, followed by S₂F₉ → SF₅ + SF₄ and SF₅ + CF ? SF₆ + C (C ? NO or C₂H₂Cl₂).     

Vibration–vibration energy exchange between 15N14NO and CO

The temperature dependence of the vibration–vibration energy transfer between the v₃ mode of ¹⁵N¹⁴NO and the first vibrational level of CO was determined over a range of 680 to 1300°K using a shock tube. Several mixtures of ¹⁵N¹⁴NO? CO were tested, diluted in 95% Ar. The resulting exothermic transfer probabilities for the reaction, are compared to previous work on N₂O—CO. The results for ¹⁵N¹⁴NO? CO exhibit a more pronounced direct temperature dependence than for N₂O—CO even though the process has a closer resonance (ΔE = 59 cm^?1 for ¹⁵N¹⁴NO? CO and ΔE = 81 cm^?1 for N₂O? CO).     

Organic crystals absorb hydrogen gas under mild conditions

We have studied the hydrogen sorption on three well-known organic hosts that possess vacant lattice voids large enough to accommodate H2 molecules.