Abstract: Various possible isomers of C₇₀O₂were studied by using AM1, PM3 and INDO methods. Forty five isomers of C₇₀O₂were investigated on the basis of the most stable structure of C₇₀O . The calculated results indicate that the structure of C₇₀O₂in which the two oxygen atoms are added to the two different 66 bonds of the same six membered ring to form epoxide at the pole of C₇₀is the most stable. The differences of energy between the isomers of C₇₀O₂in which the two oxygen atoms are added to α, α; α, β; β, β bonds and the one in which the two oxygen atoms are added to α, γ; α, ε; β, γ; β, ε bonds are about 60-80 kJ/mol. The former is more stable than the latter. By using the optimized geometries, the electronic spectra of C₇₀O₂were calculated by INDO/CI and compared with those of C₇₀and C₇₀O.

Key words: AM1, PM3, INDO, C₇₀O₂, Electronic spectra