Subject: Re: CCL:Molecular Mechanics

From: TOPPER ROBERT <[email-masked]>
Date: Mon, 27 Nov 1995 12:16:55 -0500 (EST)

> 
> On Wed, 22 Nov 1995, Robert K. Szilagyi wrote:
> 
> > 	My 0.02$ to this question is that molecular mechanical results MUST NOT
> > be compared with each other if the molecules are different. It has no chemical
> > and physical meaning at all! The MM model is constructed with different
> > equations due to the different parameters.

Hi,

Some interesting approaches to this problem have been suggested by DeTar:
for example, see J.Org.Chem. 56, 1463 (1991) and accompanying
articles. Also see DeTar, Ninzet and Darba, J.Org.Chem. 50, 2826 (1985);
ibid., 5298 (1985); ibid., 5304 (1985).

Basically, in DeTar's approach
a series of isodesmic comparisons is made to define the "formal 
steric enthalpy," which is then used to obtain 
heats of formation. The method, which is quite general, can even
be used in conjunction with ab initio methods and contains no
adjustable parameters, which is nice.

I hope this helps -
rqt

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