Dissociation Energy and Rate of Decomposition of C2N2

The decomposition of cyanogen has been studied using shock wave heating. Kinetic and equilibrium concentrations of CN were obtained spectrophotometrically on 1, 5, and 10% solutions in Ar, in the incident and reflected shock regions. These data give $${\mathrm{C}}_2{\mathrm{N}}_2\text{=2\hspace{0.17em}}\mathrm{CN}{\mathrm{,\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\Delta H}}_0^{\circ }\text{=125±8\hspace{0.17em}}\mathrm{kcal}.$$ The dissociation reaction proceeds via a second‐order process with a rate constant fitted by $$k_{\mathrm{diss}}{\text{=[(3.3×10}}^{12}{\text{)/5.5!]T}}^{\frac{1}{2}}{\mathrm{(E/RT)}}^{\text{5.5}}{e}^{\mathrm{-E/RT}}\mathrm{,\hspace{0.17em}}{\mathrm{cm}}^3\hspace{0.17em}{\mathrm{mole}}^{\text{−1}}\hspace{0.17em}{\sec }^{\text{−1}}.$$ The three‐body recombination‐rate constant is given by $$k_{\mathrm{rec}}{\text{=2.3×10}}^{12}{\mathrm{(E/RT)}}^3\mathrm{,\hspace{0.17em}}{\mathrm{cm}}^6\hspace{0.17em}{\mathrm{mole}}^{\text{−2}}\hspace{0.17em}{\sec }^{\text{−1}}\text{;\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}E=125\hspace{0.17em}000.}$$ Previous data on this reaction have been summarized and critically analyzed.