TY - JOUR
T1 - Thermodynamic measurements on unsubstituted cyclopropenyl radical and anion, and derivatives, by second harmonic alternating current voltammetry of cyclopropenyl cations
AU - Wasielewski, Michael R
AU - Breslow, Ronald
PY - 1976
Y1 - 1976
N2 - Cyclopropenyl cation has been reversibly reduced electrochemically to the unsubstituted 3-cyclopropenyl radical, and with two electrons to the unsubstituted 3-cyclopropenyl anion. Reversible thermodynamic reduction potentials for both processes have been determined using second harmonic ac voltammetry. The same technique has been used to determine thermodynamic potentials for the one- and two-electron reduction of triphenylmethyl, cycloheptatrienyl, triphenylcyclopropenyl, trimethylcyclopropenyl, tri-tert-butylcyclopropenyl, and dipropylphenylcyclopropenyl cations. Adsorption effects were detected for two of these cations at a Pt, but not at an Au, electrode. The data were used in thermodynamic sequences to evaluate the basicity of various cyclopropenyl anions; a set of pKa's ranges from +50 to +74. Another thermodynamic sequence was used to evaluate the C-O bond dissociation energy of various cyclopropenols. Two unusual effects emerge: cyclopropenyl radicals are destabilized by alkyl groups, and they also appear to be destabilized relative to unconjugated radicals.
AB - Cyclopropenyl cation has been reversibly reduced electrochemically to the unsubstituted 3-cyclopropenyl radical, and with two electrons to the unsubstituted 3-cyclopropenyl anion. Reversible thermodynamic reduction potentials for both processes have been determined using second harmonic ac voltammetry. The same technique has been used to determine thermodynamic potentials for the one- and two-electron reduction of triphenylmethyl, cycloheptatrienyl, triphenylcyclopropenyl, trimethylcyclopropenyl, tri-tert-butylcyclopropenyl, and dipropylphenylcyclopropenyl cations. Adsorption effects were detected for two of these cations at a Pt, but not at an Au, electrode. The data were used in thermodynamic sequences to evaluate the basicity of various cyclopropenyl anions; a set of pKa's ranges from +50 to +74. Another thermodynamic sequence was used to evaluate the C-O bond dissociation energy of various cyclopropenols. Two unusual effects emerge: cyclopropenyl radicals are destabilized by alkyl groups, and they also appear to be destabilized relative to unconjugated radicals.
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M3 - Article
AN - SCOPUS:0001342787
VL - 98
SP - 4222
EP - 4229
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 14
ER -