Canonical tautomers

Hello everybody,





Can someone help me by understanding what are canonical tautomers? I know about the canonical smiles but what about tautomers? Is this just their representation into smile format?





thank you in advance.





Sylvain

Hi,








 For example:





 6 tautomers are depicted on the attached figure.  





 The same canonical tautomer "O=C1NNNC(=O)C1=O"


 will be assigned to the 6 structures. 





 Generation of the canonical tautomer based on empirical chemical rules.








Jozsi

Thank you Jozsi,





So, if I well understood what you mean, the canoninal tautomer is in fact the canonical smile of the reprensentation of all the tautomers?





I have another question: are there great differences between canonical tautomers, dominant tautomers and moststable tautomers? I succeeded to create the two first types. But I had many troubles in creating the last one. Can anybody help?





Sylvain

Hi,

Quote:

So, if I well understood what you mean, the canoninal tautomer is in fact the canonical smile of the reprensentation of all the tautomers?

    The canonical tautomer will be generated as a canonical smile if you specify the





    "-f  smiles:u"  option





          For example with the cxcalc command line,

Code:

cxcalc  "OC1=NN=NC(O)=C1O" canonicaltautomer  -f smiles:u

         And the generated canonical smile representation will be this:





         "O=c1[nH][nH][nH]c(=O)c1=O"

Quote:

I have another question: are there great differences between canonical tautomers, dominant tautomers and moststable tautomers?

• The canonical tautomer generation based on an empirical rule system that is applied to    the submitted molecule.Different tautomers always have the same canonical tautomeric forms.

• The most stable tautomer generation based on a more complicated calculation since the   pK_a values of the submitted molecule also invoked in the calculation.Because of the   pK_a criteria  it can occure that different tautomers may have different most stable tautomeric forms.

• The dominant tautomer distribution based on the calculation of the tautomeric equilibrium among alternative tautomeric forms. Distribution of tautomrers given in [%].

   


Jozsi

Hi,





What an answer! Thank you for all Jozsi.





Sylvain