From: David Kelly (KellyDR$##$Cardiff.ac.uk)
Date: Thu Nov 13 2003 - 14:56:41 EST
I hope you will trust this reply..................
CAS numbers are assigned based on the structures shown in the
papers and/or some definable composition data. The classic example
is glucose for which there are numerous CAS numbers eg for the
aldehydic form, the two pyranoside anomers, the two furanoside
anomers and so on. If the paper describes the reduction of a sugar to
the polyol the authors might show the open chain aldehydic form, if
they are describing a glycosidation they might show the pyranoside
form, but it is the same chemical out of the same bottle, but with two
CAS numbers.
Beilstein generally has a preferred CAS number for a material, but
also cross references the alternatives as well. CAS also has cross
references. The confusion comes from a lack of definition in original
papers. Suppose we have an imine which can potentially exist as two
geometric isomers, but actually is always found as one isomer. There
will be two CAS numbers one for the cases where the authors have
specified the stereochemistry and another for cases where the
stereochemistry has not been specified.
Dave Kelly
Dr David R. Kelly
Dept. of Chemistry, Cardiff University, PO Box 912, Cardiff, CF10
3TB, UK
Phone 02920-874063: Fax 02920-874030
Mobile 07971-240448: Home 02920-610891
Web page http://www.cf.ac.uk/uwc/chemy/staff/kelly.html
For the "Elephants and Butterflies" article see
http://www.semiochemica.org.uk/articles/articlesidx.html
BEST Record: http://expertise.cos.com/cgi-bin/exp.cgi?id=498275
For catalysis see http://www.chemsoc.org/cgi-
shell/events/nforedisp.pl?ID=551
Cardiff University is the public name of the University of Wales,
Cardiff, a constituent institution of the
University of Wales.
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