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Research into the geometries and singlet-triplet splittings for the 10 geometrical isomers of didehydrophenol is presented. It is possible to accurately estimate the singlet-triplet splittings by correlation with proton hyperfine coupling constants in antecedent monoradicals.

A study performed ab initio calculations of the potential energy surfaces for the stereomutations of spiropentane and cis- and trans-dimethylspiropentanes. The analysis aimed to better elucidate why disrotation is apparently preferred to conrotation in the pyrolyses of both the 1,2-dimethyl- and 1,2,4-trimethylspiropentanes. It also investigated why double rotation of C-1 and C-2 in the trans-1,2,4-trimethylspiropentanes is slower than epimerization at C-4. Results are discussed.

The introduction of each trigonal center into a cyclopropane ring and its effect in the strain energy was investigated through ab initio calculations. Results have demontrated that the introduction of a trigonal center into a three-membered ring produces an additional strain. The results further demonstrated that the resulting strain was not secondary to the increase in angle strain but the loss of a strong cyclopropane bond.

Studies the role of the introduction of trigonal center into a cyclopropane ring in the strain energy increase. Ab initio calculations; Creation of additional angle strain; Effect of the loss of the cyclopropane C--H bond.