Athanor by arbastro
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How to list the tautomers of a structure

Select the structure and choose Object › Chemistry › Tautomers. The forms are listed by rule of thumb (more aromatic rings first, then C=O over C=C, then amino over imino); place one or all of them.

Steps

  1. Select the structure, for example 2-hydroxypyridine.

  2. Choose Main menu › Object › Chemistry › Tautomers.

  3. The window lists the forms one proton shift apart, and further. The one you drew is marked As drawn.

    The 4 tautomers of 2-hydroxypyridine, with 2-pyridone first and the drawn form marked As drawn.The 4 tautomers of 2-hydroxypyridine, with 2-pyridone first and the drawn form marked As drawn.

  4. Press Place under a form, or Place the other ones together.

Prediction

The order is a rule of thumb: more aromatic rings first, then C=O over C=C, then amino over imino. It is not a distribution. How much of each form there is depends on the solvent, and no model with published accuracy for it runs here.

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Last updated Nov 12, 2026