γ Radiolysis of Liquids at High Pressures. IX. Cyclopentane and Its Solutions with N2O, ND3, and C2H5OD

Abstract

The γ radiolysis of cyclopentane and its solutions with N2O, ND3, and C2H5OD was studied at room temperature and at pressures in the range 0–6.2 kbar. For pure cyclopentane at 1 atm (0 kbar), G(H2) = 5.2, G(bicyclopentyl) = 1.3, G(cyclopentene) = 3.0, and G(pentene-1) = 0.70. The yields of hydrogen and bicyclopentyl are independent of pressure. The yields of cyclopentene and pentene-1 decrease with increase in pressure, and at 6.2 kbar both yields are ∼ 10% smaller than the values at 1 atm. Yields of several unidentified minor products (G < 0.1 at 1 atm) show the largest pressure dependence. Such results are discussed in terms of possible effects of pressure on competitive decay modes of cyclopentane excited states, and ΔV‡ (disproportionation) − ΔV‡ (combination) for cyclopentyl radicals is estimated to lie in the range 0–1 ml mole−1. For 0.06M N2O solutions, the observed pressure independence of G(N2) = 3.0 and G(H2) = 3.7 indicates no effect of pressure on the yield of scavenged electrons. For both 0.06M ND3 and 0.32M C2H5OD solutions, G(H2+HD+D2) = 5.2 at all pressures. However, for both solutions, G(HD) increases with increase in pressure and at 6.2 kbar is ∼ 35% larger than the value at 1 atm. The increase in G(HD) with pressure is attributed to an increase in the yield of cations scavenged from geminate cation–electron pairs. Such an effect of increased pressure can be understood in terms of a viscosity-independent decrease in the electron diffusion coefficient (via an effect on the depth and concentration of electron traps) or an increase in the positive-charge diffusion coefficient (via an enhancement of positive-hole conduction).