The reactions of tert-butoxyl radicals, generated by the pyrolysis of di-tert-butyl peroxide with cyclohexane and a number of methyl-substituted cyclohexanes have been studied. The Arrhenius parameters corresponding to overall hydrogen abstraction have been determined in the temperature range 399-434 K based on the values of the Arrhenius parameters for pressure-dependent decomposition of tert-butoxyl radicals obtained by Batt and Robinson (L. Batt and G. N. Robinson, lnt. J. Chern.

Thermodynamic data for the binding of Ag', Pb2+ and Cd2+ nitrates with dibenzo-18-crown-6 in acetonitrile-, water solvents have been obtained in the temperature range 288-308 K using a conductometric technique. The observed molar conductivities, A, were found to decrease significantly for mole ratios less than unity. The conductivity data have been analysed using a model involving 1 : 1 stoichiometry. The stability constant, K , and the limiting molar conductivity, A , , for each 1 : 1 complex have been obtained from the measured conductivities by using a non-linear least-squares curve-fitting procedure. The complexation sequence, based on the value of log K at 298 K, was found to be Pb2+ > Cd2+ > Ag+. The significance of the reported values of AHo and ASo in the present work has been discussed.

MINDO-Forces calculations have been performed with complete optimization of the geometry on cyclobutanone and its enol counterpart, perfluorination of cyclobutanones and enol counterparts, and X-cycolobutanones and their X-enols, where X is NO 2 , CF 3 , CN, OH, NH 2 and F. It was found that ketone is more stable than its enol counterpart. Perfluorination destabilizes ketone on the expense of enol. These results agree with experimental and theoretical calculations. Electron releasing substituents (NH 2 , OH, F) stabilize cyclobutanone, while electron withdrawing substituents (CF 3 , NO 2 ) destabilize it. CN substituents have almost no effect on the stabilization of this keto-enol system.Geometrical parameters, heats of formation, electron densities and Gibbs free energy are reported.

The use of sodium to dry carbon tetrachloride as described in the experimental section was an extremely unwise procedure as this mixture of chemicals can lead to violent explosions.' Under no circumstances should this method be adopted by others as alternative safe methods for drying carbon tetrachloride are available.'