Maybe this helps for the “SMILES bond order problem” at least temporarily (setting the usearo flag to false is important):

http://cactus.nci.nih.gov/chemical/structure/c1cccc2c1c(c(\C=C)n2)CCN/smiles?usearo=false
NCCC1=C([NH]C2=CC=CC=C12)C=C

http://cactus.nci.nih.gov/chemical/structure/c1ccccc1/smiles?usearo=false
C1=CC=CC=C1

benzene (Compound #236) gives now 1.45 ppm for 1H and 27.1ppm for C13 (Mon, May 3rd 2010m 7:26am MET; screendump available on request), obviously again lost double bonds.

1) Please keep in mind that ‘Chemspider’ and Tony Williams have established a lot of reputation within the scientific community – this is the best way to destroy it !
2) Open Software and Open Data doesnt mean that every program is untested
3) I have detected this error a long time ago and have written a private email to Tony, because I think this topic is not suitable for my webpage located on http://nmrpredict.orc.univie.ac.at/chemspider_nmrshiftdb.html; on this webpage only problems showing that NMRSHIFTDB is state-of-the-art of ca. 1980 are summarized.
4) When you know that the problem is connected to some parser-error dealing with double bonds then YOUR RESPONSIBILITY IS TO TEST THAT BEFORE (!!!!!!!) you make it available to the community. I think it is NOT an obscene desire, that a program author of a prediction program has tested his/her program with benzene. Maybe a second test with a heterocycle like imidazole can be expected by the community – maybe only when your ‘Open Time’ allows that !

Recommendation for Chemspider users: Do a prediction on Chemspider, then take a textbook and apply the ‘old’ increment rules, if you are still unsure apply another prediction program like ACD, KnowItAll, NMRPredict, SPECINFO …….. be careful, those programs produce reliable values, but they are not free-of-charge ! Hopefully, you understand now, why those programs are NOT FREE-OF-CHARGE ! They are tested und the underlying data are curated !

Have a nice day ! Wolfgang Robien

The NMRShiftDB is then left to guess where the double bonds are, which is tricky, and the CDK does not have a universal solution. I do not know what solution the NMRShiftDB is using, but please do consider having ChemSpider send SMILES *with* explicit bond orders.

Say what you want; say what you mean. Semantic chemistry starts with being explicit with your data, and not with wrapping in CML or RDF