I don't agree with Mathematica's classification of this structure as a purine. If you buy their apparent premise that you can break double bonds and introduce unmentioned hydrogen atoms just by saying "methyl", though, then the numbering is correct. Look up "purine" in Wikipedia and you'll see the official atom numbering. Wikipedia says caffeine is a xanthine, which seems right to me. On Sat, Feb 9, 2019, 1:06 AM Bill Gosper <billgosper@gmail.com wrote:
In[38]:= ChemicalData["Caffeine", "IUPACName"]
Out[38]= "1,3,7-trimethylpurine-2,6-dione"
agreeing with https://en.wikipedia.org/wiki/Caffeine#Chemistry in both structural formula (ChemicalData["Caffeine"]) and name. Why isn't it 1,3,7-trimethylpurine-2,9-dione? I.e., Why does the imidazole (pentagonal) ring count for the methyls, but not the -ones? —rwg _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun