Radical cations generated from 1-cyclopropylnaphthalene (1), 1-bromo-4-cyclopropylnaphthalene (2), and 2-cyclopropylnaphthalene (3) were studied electrochemically. Oxidation of all these substrates in CH3CN in the presence of CH3OH leads to cyclopropane ring-opened products, i.e., the corresponding (1,3-dimethoxypropyl)naphthalenes. However, the rate constant for methanol-induced ring opening (Ar-c-C3H5.(+) + CH3OH --> ArCH-((.))CH2CH2O(H+)CH3) is extremely small (<20 M-1 s(-1) for the alpha-cyclopropylnaphthalenes) despite the fact that ring opening is exothermic by nearly 30 kcal/mol. These results are explained on the basis of a product-like transition state for ring opening wherein the positive charge is localized on the cyclopropyl group, and thus unable to benefit from potential stabilization offered by the aromatic ring.