G. J. Hoijtink1, E. de Boer1, P. H. van der Meij1, W. P. Weijland1
1Chemical Laboratory of the “Vrije Universiteit”, Amsterdam
Tóm tắt
AbstractPotentiometric titrations of solutions of various aromatic hydrocarbons in 1,2‐dimethoxyethane and tetrahydrofuran with a solution of biphenylsodium have shown chemical reduction to proceed in two stages:
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The reduction potentials of the aromatic hydrocarbons, calculated from the potentiometric curve, are in good agreement with the half‐wave potentials obtained from polarographic reductions in 96% dioxan‐water. The standard potentials of the first reduction step expressed in Volts against the standard potential of biphenyl fit the following equation:
with γ = ‐ 2.19 ± 0.059 e.V. (2 × stand. dev. from mean) in which a stands for the root of the m.o. secular equation (overlap S = 0.25 included) corresponding to the lowest non‐occupied π‐orbital of the hydrocarbon and γ is the resonance‐parameter.The electrochemical series of aromatic hydrocarbons including a rough estimate of the standard potential of sodium in 1,2‐dimethoxyethane and the mechanism of chemical reduction in inert and proton‐active solvents are discussed.
