Subject: Re:Unrelated Questions

From: [email-masked] (STEPHEN ANDRUSKI)
Date: Wed, 28 May 1997 10:42:10 -0500

>>Question 1:  In order to obtain Mulliken partial atomic charges for 
     >>some work in which we are engaged, I prepared a Z-matrix for the 
     >>molecule p-tolylacetylene ("tolac.mop"), as follows:

     >>am1 nointer
     >>p-tolylacetylene
     
     The problem is with the specific way the atoms are defined in the 
     Z-matrix.  This is a common problem with linear molecules in MOPAC.  
     You can try defining the Z-matrix in a different way and this 
     sometimes solves this kind of problem, but in this case that may not 
     be possible.  Using the keyword "nointer" only keeps the internal 
     coordinates form printing.  Using the keyword "xyz" will run the 
     calculation in cartesian coordinates and should allow it to run 
     properly.

     >>Question 2:  I would like to know if there is some established 
     >>quantitative measure of the "degree" of chirality.
     
     While a measure of the similarity between two enantiomers might have 
     some utility (though I'm not sure what), the idea that one compound is 
     "more chiral" than another one makes no sense to me.  If anything, the 
     number of chiral centers would make more sense as a measure of the 
     amount of chirality, but even then I still don't see the utility of 
     the concept.  Perhaps you could elaborate on how this concept would be 
     used.
     
     Dr. Stephen W. Andruski
     FMC Corporation
     [email-masked]