Subject: Re: CCL: Chirality

From: "Dr. Rudolf Herrmann" <[email-masked]>
Date: Wed, 28 May 1997 21:24:13 GMT

On 22 May 97 at 10:03, Hr. Dr. S. Shapiro wrote: 
> 
> Question 2:  I would like to know if there is some established quantitative
> measure of the "degree" of chirality.  For example, consider the chiral
> molecules CR1R2R3R4, where in one case R1 = H, R2 = D, R3 = T, and R4 = F,
> whereas in another case R1 = H, R2 = naphthyl, R3 = n-octyl, and R4 = NO2.
> Whilst both molecules are chiral, it is clear that the structural variation
> when R1 = H, R2 = naphthyl, R3 = n-octyl, and R4 = NO2 makes this a "more"
> chiral molecule than when R1 = H, R2 = D, R3 = T, and R4 = F.  But how to
> express in a quantitative fashion that the second chiral molecule is "more"
> chiral than the first?  I thought that perhaps the RMS deviation between the
> two enantiomorphs of each of these chiral molecules might provide
> quantification of chirality.  Does anyone have any further, possibly better,
> suggestions?
> 

Dear Dr. Shapiro,

there has already a lot of work been done on the problem of how to 
quantify chirality. Most approaches have some merits, but none is 
completely satisfying. I will just quote a few references and leave 
the judgement to you:

Very good review article on the problem "what is the most chiral 
tetrahedron"; see also the literature quoted therein:
A.B.Buda, T.Auf der Heyde, K.Mislow, Angew.Chem 104 (1992) 1012.

Chirality functions:
E.Ruch, I.Ugi, Top.Stereochem. 4 (1969) 99; Angew.Chem. 89 (1977) 67.

Chiral genus:
J.Dugundji, R.Kopp, D.Marquarding, I.Ugi, Top.Curr.Chem. 75 (1976) 
165.

On the problem how to reconcile theory (or should I say philosophy) 
with experiment:
K.Mislow, P.Bickart, Isr.J.Chem. 15 (1976/77) 1.

You may also have a look to quantum-chemical treatment of chirality:
M.Quack, Angew.Chem. 101 (1989) 588.

Hope this will help you.

Yours sincerely,
R.Herrmann.

Dr. Rudolf Herrmann
Institut fuer Organische Chemie und Biochemie der 
Technischen Universitaet Muenchen
Lichtenbergstr. 4
D-85747 Garching
Tel. + 49 - 89 - 28913325
Fax  + 49 - 89 - 28912727