Subject: optical activity prediction: SUMMARY

From: "Prof. Robert Topper" <[email-masked]>
Date: Mon, 8 Feb 1999 11:34:48 -0500 (EST)

Greetings to all the CCL subscribers,

I'd like to thank everyone who responded to the following question about
predicting the optical rotation of an enantiomer, and thence the
optical activity of a mixture of enantiomers.

A summary of the responses is attached. I've only included responses
which directly provided information relevant to the question, but
I am also grateful to those who responded but have not been included.

Gratefully yours,
Robert Topper

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Prof. Robert Q. Topper                  email:   [email-masked]
Department of Chemistry                 phone:   (212) 353-4378
The Cooper Union                        fax:     (212) 353-4341
51 Astor Place                          subway:  take the 6 to Astor Place 
New York, NY 10003                               and you're there!
                 http://www.cooper.edu/engineering/chemechem/
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Original question:

An organic chemist with whom I collaborate has asked me
whether it is possible to predict the optical activity
of a mixture of enantiomers, even semiquantitatively.
(i.e., is the optical activity "big" or "small" for
a given enantiomeric excess, or e.e.).

My own search of the Internet has failed to turn up anything.
Can anyone give us any suggestions? 

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From: "Dr. Mike Gilson" <[email-masked]>

I don't know how far along things are, but
this topic was discussed in a recent C&E News.
I am pretty sure the work came from Beratan's
group at Pittsburgh.

Good luck,

Mike
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Michael K. Gilson, Ph.D., M.D.                         Phone:   (301) 738-6217
Center for Advanced Research in Biotechnology          Fax:     (301) 738-6255
National Institute of Standards and Technology
9600 Gudelsky Drive	        http://www.carb.nist.gov/carb/gilson.html
Rockville, MD  20850-3479       e-mail: [email-masked]
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From: James T Metz <[email-masked]>

Robert,

     See Kondru, R.K. et al. JACS (1998) 120, 2204.  The ab initio program
DALTON was used to estimate optical activity for chiral fragments of a natural
product by calculation of the electric dipole magnetic dipole polarizability
tensor.

                              Jim Metz
                              [email-masked]
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From: "James G. Macmillan" <[email-masked]>
(First of two messages)

Robert,

Is the question "Can you predict the rotation of a chiral molecule from it's
structure?" or "Can you predict the rotation of a mixture of enantiomers?"?

The first question is very difficult and I can not help you with it.  I
believe there are theoreticians working on the problem but I am not up on
how good they have gotten in predicting rotation of chiral molecules.

The second question is straight forward.  The rotation of a mixture of
enantiomer is given as the sum of the rotation of each enatiomer times its
mole fraction. I am sure you know this.  It would mean for an enantiomer
with a rotation of +20 that contained 20% the other enantiomer the solution
rotation would be .2 (-20) + .8 (+20) = +12.  Of coarse, a 50/50 mixture
would have zero rotation. .5(-20) + .5(+20) = 0.

Jim

> From: TOPPER ROBERT [mailto:[email-masked]]
>
>
> Yes, the former. Or, said another way, how can you predict the
> ROTATION of a particular enantiomer? (+20 and -20 in your example).
>
> robert
>

From: "James G. Macmillan" <[email-masked]>
(Second of two messages)

Robert,

That is a tough one.  The octant rules (Introduction to Organic
Spectroscopy; J. B. Lambert, H. F. Shurvell, D. Lightner, and R. G. Cook;
page 271- 274, Macmillan Pub. Co. 1987) allow you to make a prediction on
the sign of the CD curve.  These rule can also be found in C. Djerassi,
Optical Rotatory Dispersion, McGraw Hill, New York, 1960.  Again, these are
empirical rules not theoretical based.

Jim
**********************************************
James G. Macmillan, Ph.D.
Department of Chemistry
University of Northern Iowa
Cedar Falls, IA 50614-0423

Ph: (319) 273-2476 FAX: (319) 273-7127
E-mail: [email-masked]
ICQ: 10405682
********************************************
"Where good wine flows so does good conversation"

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From: Karl Irikura <[email-masked]>

Hi.  Have you checked recent papers by Dave Beratan?  I think he has
had some success, using CADPAC as the basic tool.

Good luck,

Karl I.

----------------------------------------------
Dr. Karl K. Irikura
National Institute of Standards and Technology
100 Bureau Drive, Stop 8380
Gaithersburg, MD  20899-8380
voice: 301-975-2510	fax: 301-869-4020
e-mail: [email-masked]
http://www.nist.gov/compchem/
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From: Iraj Daizadeh <[email-masked]>

Dear Professor Topper:

I refer you to a recent paper from a group from U-Pitts; references for
the question you pose may be addressed there.  If not; the paper is still
a very good read.

Kondru, RK; Wipf, P; Beratan, DN.
Atomic contributions to the optical rotation angle as a quantitative probe
of molecular chirality. SCIENCE, 1998 DEC 18, V282 N5397:2247-2250.

Best regards,

Iraj.

Iraj Daizadeh, Ph. D.
Harvard University
Department of Cellular and Molecular Biology
The Biological Laboratories, Box #140
16 Divinity Avenue
Cambridge, MA 02138
Phone: (617) 495-0783
       (617) 495-0560
Fax:   (617) 496-4313
Email: [email-masked]

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From: [email-masked] (Christopher Cramer)

Robert,

Beratan at Pitt has published on prediction of optical rotations. 
Several references are on his web page
(http://www.chem.pitt.edu/faculty/beratan.html)

Chris

Christopher J. Cramer
University of Minnesota
Department of Chemistry
207 Pleasant St. SE
Minneapolis, MN 55455-0431
--------------------------
Phone:  (612) 624-0859 || FAX:  (612) 626-2006
[email-masked]
http://pollux.chem.umn.edu/~cramer
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From: "Christoph M. Koelmel" <[email-masked]>

Hi,

enantiomers have opposite specific rotations (rotation angle normalized
with respect to length of path light has to go through and concentration
of the substance that is optically active), and if one assumes small concentrations, the 
rotation angle is then just proportional to the 
difference of the concentrations of the two enantiomers, I would think.

http://www.scimedia.com/chem-ed/spec/molec/polarim.htm might be useful.

A different question is how to compute the specific rotation for an
enantiomer. 

The DALTON program site, e.g. at http://ithaka.ki.ku.dk/QC/dalton/Master.html
may be a useful starting point.

Cheers,

Christoph
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From: Huub van Dam <[email-masked]>

Hello Robert,

As far as I know the optical activity of a mixture of enantiomers is just a
linear interpolation of the optical activities of the pure enantiomers. Here
optical activity means the amount by which the plane of polarisation of linearly
polarised light is rotated by the optical active species.

Another measure is related to circulardichroism. In this case the spectra of
enantiomers are measured using circularly polarised light. Depending on the
enantiomer and the direction of polarisation the spectra show remarkable
differences.

The circulardichroism spectra can be calculated by a few programs. For example
Stefan Grimme has a DFT code that seems to obtain very accurate results, his
webpage is at

    http://pcgate.thch.uni-bonn.de/tc/grimme.html

you may want to look up a few of his papers.

Kind regards, Huub van Dam

=============================================================

Huub van Dam                               E-mail: [email-masked]
CCLRC Daresbury Laboratory                  phone: +44-1925-603362
Daresbury, Warrington                         fax: +44-1925-603634
Cheshire, UK
WA4 4AD

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From: "Dr. S. Shapiro" <[email-masked]>
Dear Sir;

     There are all sorts of rules relating to the prediction of optical activity
of enantiomers.  Some of these you may find in Caldwell & Eyring's "The Theory
of Optical Activity", though this is rather dated.  From what I remember the
best predictions of optical activity are in the IR range rather than, say, at
the sodium D-line.  For further details, please consult a brief review article
in Enantiomer 1: 151-166 ('96), an article entitled "Chemical and spectroscopic
methods for determining absolute configurations of chiral alcohols".

Tschuess,

S. Shapiro
[email-masked]

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From: "Frank J. Devlin" <[email-masked]>

Hi Robert,

Take a look at Beratan's article in Science, 282, 2247 (1998).

Regards,

Frank Devlin.
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From: Craig Burkhart <[email-masked]>

Robert,

There was an article in a recent Chemical & Engineering News (within the last
month) where there was a brief about the calculation of absolute optical
rotation. To my knowledge, this was the first ab initio ("ab initio" in this
sense not necessarily meaning quantum chemical) prediction of optical rotation.

This has been a topic that has come up, off-and-on, throughout the last few
years. I have always said, "I don't know how to do that"; but it appears that it
may now be possible. So rifle through your most recent C&E News magazines and
you will find it (or search for it online on the ACS web site).

Craig

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From: Ricardo Nunez <[email-masked]>

Dear all,
	Our group have developed a method to calculate the
optical activity from molecular geometry, I give you some
references:

J. Mol. Struct., vol. 354, (1995) 81-87
J. Mol. Struct., vol. 442, (1998) 135-143
J. Mol. Struct., vol. 447, (1998) 127-133

Ricardo Nunez Miguel
[email-masked]
Departamneto de Quimica Organica
ETS de Ingenieros Industriales
Universidad de Valladolid
Spain