"No Barrier Theory" asserts that when only one thing happens in a chemical reaction there is no kinetic barrier, but only a quadratic potential function, and that the kinetic barriers associated with almost all chemical reactions result form the need for more than one simple thing to happen simultaneously for the reaction to occur. This theory permits calculation of the free energies of activation for chemical reactions given only the equilibrium constants in solution and the distortion energies corresponding to the hypothetical "one thing at a time" transformations. The calculations are much less demanding than direct calculation of the structure and energy of the solvated transition state and generally come within 2 kcal of the observed value.

This approach has now been applied to the addition of thiols and sulfite to carbonyl compounds. As has been shown for the addition of water to carbonyl compounds, the No Barrier Theory approach allows calculation of the rate constants corresponding to a mechanism of reaction.

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