Subject: Semi-empirical S-charges II

From: "E.E.Moret" <[email-masked]>
Date: Mon, 27 Jun 94 13:35:16 METDST

Dear colleagues,

With regards to the question about 'sensible' charges on sulfur atoms:

The first responses to my question have arrived (thanks) and suggest to me
that I need to clarify 2 things:

- the CH3-SO2-NH-CH3 is only a test model for the sulfonamide containing
bioactive compounds with approximately 100 atoms. Large basis set ab initio
calculations could only be applied to part of the molecules.
- Potential derived charges may be the best for modelling purposes and they
may be less basis set dependent. Is this correct, even if the basis set
lacks incorporation of d-orbitals?
I calculated the ESP (Bessler, Merz, Kollman) charges with Mopac93:

Molecule Ch3-SO2-nh-ch3 (important atoms in capital letters):

Atom          Mulliken        ESP
C             -0.82           -0.99
S              2.53            2.45
N             -0.78           -0.96
O             -0.84           -0.78
O             -0.91           -0.88

I will summarise the reponses for CCL.

Bests regards,
Ed Moret
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E.E. Moret	(@more@)			    [email-masked]
Computational Medicinal Chemistry/Department of Pharmaceutical Chemistry
Faculty of Pharmacy/Utrecht University/the Netherlands
Telephone	(31-30)536979/536958        Facsimile      (31-30)516674
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