Evaluating Tautomer Standardization Rules using Tautobase
Ingvar Lagerstedt and Roger A. Sayle
Tautobase contains ratios for 1680 tautomer pairs, distilled from the work of Peter Taylor and Peter Kenny. The reported ratios is a mix of experimental and estimated values. We presented here a partial implementation of these rules in rxnfix, a program for reaction normalisation. Issues discussed include:
– should some rules be ignored, i.e., when the distribution is close to 50-50
– how far can one extrapolate, i.e., between halogen or carbonyl substituents
– should only values from water be include, distribution is often very different in gas phase/apolar solvents
One early lesson is that it is better to apply rules on fully kekulized structures, then on structures just indicating aromatic bonds.