The electrochemical oxidation and reduction of 11 spiro compounds have been investigated in ACN and DMF. The reversible voltammograms were obtained only for nitro and Cl substituted spiro compounds for reduction and oxidation, respectively. Oxidation potentials are more sensitive to the structural differences and the type of substituent than reduction potentials. The reduction potentials were in the range of -1.22 to -1.28 V vs see, which is in the range of reduction potentials expected for substituted nitro-benzenes. Semi-empirical quantum mechanical calculations carried out on MeO- and NO2-substituted chloro spirobenzopyrans focus on the determination of the enthalpies of the samples and comparison with the oxidation potentials of the same samples. (C) 1997 Elsevier Science Ltd.