Subject: Re: CCL:G:sulfur containing compounds

From: sc18 <[email-masked]>
Date: Tue, 03 Jun 1997 18:40:15 -0500

Hi,

I've been working with these kinds of compounds for a couple of years. 
See K.R.Fountain, et al. J.Org. Chem., 1997,2738, vol. 62, for
computations on the dimethylsulfonium salts.  We also have an article
earlier this year (same journal) on the leaving group behavior of these
compounds.

Sincerely,

Ken Fountain
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From: Alan Shusterman <[email-masked]>
Date: Tue, 03 Jun 1997 16:53:20 -0700 (PDT)

Hi 
	Its not surprising that HF and becke3LYP gave very different results
for orbital energies. Theoretically, the HF and DFT orbital energies need not
(should not) agree.
	You don't say what you want the HOMO values for, but if you are trying
to estimate the ionization potential then any of the following methods should
prove useful:

AM1
PM3
HF/3-21G(*)
HF/6-31G*

Alan Shusterman
Department of Chemistry
Reed College
Portland, OR
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From: Stefan Fau <[email-masked]>
Date: Wed, 04 Jun 1997 10:22:29 -0600 (MDT)

Hi ,

the different results for HF and DFT(B3LYP) are not surprising, since DFT 
includes a part of the correlation energy, which is important for (distorted) 
aromatic systems. Therefore either a well parametrized semiempirical method or 
DFT should be appropriate. It would be a good idea to check the results of the 
calculations against good literature values of Delta(H) for an isodesmic 
reaction like Me2S + PhS(O)Me --> Me2SO + PhSMe if you are interested in energy 
differences.

Maybe somebody else can tell you more specifically about methods that give good 
results with your molecules.
                                 Stefan
__________________________________________________________
 | Stefan Fau                [email-masked] |
 |                                                     |
 | FB Chemie der Philipps-Universitaet Marburg         |
 | Hans-Meerwein-Str.                                  |
 | D-35032 Marburg                                     |
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