On Fri, Apr 14, 2017 at 1:37 AM, Robert Hanson <hans...@stolaf.edu> wrote: > Can someone shed some light on how this brilliant statement: > > Rule 3. When two ligands differ only in that one has an atom > or atom-group of higher rank in a cis-position and the > other in a trans-position to the core of the stereogenic > unit, then preference is given to the former. > > [Mata, Lobo, et al., J. Chem. Inf. Comput. Sci. 1994, 34, 491-504] > > Got turned into this monster? > > Rule 3: ... seqcis = 'Z' precedes seqtrans = 'E'. > > In other words, rather than being able to assign priority by the very clever > method of just following the path, one has to actually assign all the > priorities of the double bonds first (from scratch, presumably, not the > currently working process) then continue.
No, not even that is sufficient. You can have of course stereo double bonds determining the fate of an atom stereo center which are themselves E/Z only by virtue of having substituents which differ only in R and S - which then need to be determined first to get the double bond descriptor. You cannot determine atom and bond stereochemistry independently in the CIP system. This must be a single, repetitive, interwoven process. Please keep us posted on your implementation line count ;-) > > Or, maybe what I am saying is, they were so close and yet didn't see that it > could have been so so simple. But no.... > > [I suppose the writer of this rule is on this list, right?....] > > > Bob > > > -- > Robert M. Hanson > Larson-Anderson Professor of Chemistry > St. Olaf College > Northfield, MN > http://www.stolaf.edu/people/hansonr > > > If nature does not answer first what we want, > it is better to take what answer we get. > > -- Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900 > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Blueobelisk-discuss mailing list > Blueobelisk-discuss@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/blueobelisk-discuss > -- Wolf-D. Ihlenfeldt - Xemistry GmbH - w...@xemistry.com Phone: +49 6174 201455 - Fax +49 6174 209665 --- xemistry gmbh – Geschäftsführer/Managing Director: Dr. W. D. Ihlenfeldt Address: Hainholzweg 11, D-61462 Königstein, Germany HR Königstein B7522 : Ust/VAT ID DE215316329 : DUNS 34-400-1719 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Blueobelisk-discuss mailing list Blueobelisk-discuss@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/blueobelisk-discuss
