Tautomerization and tautomer models of ChemAxon

You can read about the different tautomer methods of ChemAxon and their usage on this page.

Introduction

This page describes the different tautomerizaion methods of ChemAxon, and how they are used for various chemical scenarios. For a brief chemical introduction on what tautomerization/a tautomer is, please read this page.

Tautomerization methods and their results

The tautomerization method is used to generate a set of molecules (can be a single molecule as well) based on a set of tautomerization rules for a given chemical scenario, e.g. chemical searching, predicting tautomer distribution in water.

The tautomer generation algorithm

The tautomer generation algorithm goes as follows:

  1. Identifying a set of possible donors and acceptors of the input molecule that can take part in tautomerization.

  2. Filtering this set based on the pre-set tautomerization method and other parameters. The tautomerization method applies a set of tautomerization rules, which filters the original donor/acceptor set.

  3. Considering bond path length between identified donor and acceptor atoms, and filtering the set based on pre-set lengths.

  4. Generating the result tautomer set after this initial pre-processing.

The tautomerization methods

All Tautomers

The All Tautomers tautomerization does not apply any filtering rules on the original donor/acceptor set, so it is only filtered based on the pre-set parameters by the user. The original donor/acceptor set is then used during combinatorical enumeration of all tautomers (step #4).

Example

In case of 1,3-dimethyl-1H-pyrazol-5-ol we get the following tautomer set as output:

images/download/attachments/51036315/pyrazol_all.png

Normal All Tautomers

The Normal tautomer generation scope can be applied to filter the All Tautomer set. The Normal scope narrows down the original donor/acceptor set by applying empirical rules that results in a chemically more relevant tautomer set.