Further Studies on the Reaction of Cyclopentane with Mercury-6(3P1) Atoms

Abstract

A further investigation has been made of the reaction of cyclopentane with Hg6(³P₁) atoms at 29.30±0.01°C, under static conditions. Analyses, using mass spectrometric techniques, confirm that the only direct products of the reaction are hydrogen, bicyclopentyl, and cyclopentene. No evidence was found for decomposition of the cyclopentane ring. The kinetics of the reaction can be satisfactorily explained in terms of the following general mechanism:(1) $$\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n}}+\mathrm{Hg}{\text{6(}}^3{P}_1\mathrm{)\to }\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−1}}+\mathrm{H}+\mathrm{Hg}{\text{6(}}^1{S}_0\mathrm{),}$$ (2) $$\mathrm{H}+\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n}}\to {\mathrm{H}}_2+\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−1}},$$ (3) $$\text{2(}\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−1}}\mathrm{)\to }\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−2}}+\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n}},$$ (4) $$\text{2(}\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−1}}\mathrm{)\to }\mathrm{bicyclo}\hspace{0.17em}{\mathrm{C}}_{\text{2n}}{\mathrm{H}}_{\text{4n−2}},$$ (5) $$\mathrm{H}+\mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−2}}\to \mathrm{cyclo}\hspace{0.17em}{\mathrm{C}}_n{\mathrm{H}}_{\text{2n−1}}.$$ Reaction (5) can be ignored at high substrate pressures or low extents of decomposition. The limiting high‐pressure values for the quantum yields of cyclopentane disappearance, hydrogen formation, and cyclopentene formation are 0.90, 0.49, and 0.078, respectively. From the steady‐state treatment of the mechanism coupled with the quantum yield data, the ratio k₄/k₃, the ratio of the rates of recombination to disproportionation for cyclopentyl radicals, was determined to be 5.3.