From chemistry-request@www.ccl.net Mon Feb 8 11:35:21 1999 Received: from magnum.cooper.edu (magnum.cooper.edu [199.98.16.4]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id LAA10473 Mon, 8 Feb 1999 11:35:20 -0500 (EST) Received: from robin.cooper.edu by magnum.cooper.edu with SMTP id AA01553 (5.65c/IDA-1.4.4 for ); Mon, 8 Feb 1999 11:34:39 -0500 Received: by robin.cooper.edu (SMI-8.6/SMI-SVR4) id LAA05327; Mon, 8 Feb 1999 11:34:48 -0500 Message-Id: <199902081634.LAA05327@robin.cooper.edu> Subject: optical activity prediction: SUMMARY To: CHEMISTRY@www.ccl.net Date: Mon, 8 Feb 1999 11:34:48 -0500 (EST) From: "Prof. Robert Topper" Cc: topper@cooper.edu (TOPPER ROBERT), bove@cooper.edu (BOVE JOHN) X-Mailer: ELM [version 2.4 PL23] Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII 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 ***************************************************************************** Prof. Robert Q. Topper email: topper@cooper.edu 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/ ***************************************************************************** xxxxxxxxxxxxxxxxxxxxxxxxxx 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? xxxxxxxxxxxxxxxxxxxxxxxxxx From: "Dr. Mike Gilson" 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 ------------------------------------------------------------------------------ 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: gilson@carb.nist.gov ------------------------------------------------------------------------------ xxxxxxxxxxxxxxxxxxxxxxxxxx From: James T Metz 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 Metz_James_T@Lilly.com xxxxxxxxxxxxxxxxxxxxxxxxxx From: "James G. Macmillan" (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:topper@cooper.EDU] > > > 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" (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: macmillan@uni.edu ICQ: 10405682 ******************************************** "Where good wine flows so does good conversation" xxxxxxxxxxxxxxxxxxxxxxxxxx From: Karl Irikura 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: karl.irikura@nist.gov http://www.nist.gov/compchem/ ---------------------------------------------- xxxxxxxxxxxxxxxxxxxxxxxxxx From: Iraj Daizadeh 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: daizadeh@fas.harvard.edu xxxxxxxxxxxxxxxxxxxxxxxxxx From: cramer@pollux.chem.umn.edu (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 cramer@pollux.chem.umn.edu http://pollux.chem.umn.edu/~cramer xxxxxxxxxxxxxxxxxxxxxxxxxx From: "Christoph M. Koelmel" 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 xxxxxxxxxxxxxxxxxxxxxxxxxx From: Huub van Dam 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: h.j.j.vandam@dl.ac.uk CCLRC Daresbury Laboratory phone: +44-1925-603362 Daresbury, Warrington fax: +44-1925-603634 Cheshire, UK WA4 4AD ============================================================= xxxxxxxxxxxxxxxxxxxxxxxxxx From: "Dr. S. Shapiro" 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 toukie@zui.unizh.ch xxxxxxxxxxxxxxxxxxxxxxxxxx From: "Frank J. Devlin" Hi Robert, Take a look at Beratan's article in Science, 282, 2247 (1998). Regards, Frank Devlin. xxxxxxxxxxxxxxxxxxxxxxxxxx From: Craig Burkhart 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 xxxxxxxxxxxxxxxxxxxxxxxxxx From: Ricardo Nunez 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 rnunez@sorolla.eis.uva.es Departamneto de Quimica Organica ETS de Ingenieros Industriales Universidad de Valladolid Spain