Comments on: Molecular Weight Search on ChemSpy http://www.sciencebase.com/science-blog/molecular-weight-formula.html Science Blog from Freelance Science Writer David Bradley Wed, 17 Mar 2010 14:22:25 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: sciencebase http://www.sciencebase.com/science-blog/molecular-weight-formula.html/comment-page-1#comment-717 sciencebase Wed, 24 May 2006 19:07:19 +0000 http://www.sciencebase.com/science-blog/molecular-weight-formula.html#comment-717 Jonathan Goodman of the University of Cambridge emailed me to explain a little about the inner workings of HRMS and the applet: 'Small high-resolution molecular weights are usually almost integers - and so they carry less information than might be expected. H76 F2 K Mg3 Na3 S5 matches 454.34 very well, for instance, but is not a very convincing looking molecule. There are dozens of other matches to 454.34000000 For CHNO, with chemical sense-checking it is C7 H34 N24 I am not sure quite how sensible this is - the sense-checking might need upgrading. Without checking that the molecule is conceivable, it suggests C10 H52 N3 O15 which matches slightly better, but cannot be a classical molecule" Give it a try with your HRMS! Jonathan Goodman of the University of Cambridge emailed me to explain a little about the inner workings of HRMS and the applet:

‘Small high-resolution molecular weights are usually almost integers – and so they carry less information than might be expected.

H76 F2 K Mg3 Na3 S5 matches 454.34 very well, for instance, but is not a very convincing looking molecule. There are dozens of other matches to 454.34000000

For CHNO, with chemical sense-checking it is C7 H34 N24

I am not sure quite how sensible this is – the sense-checking might need upgrading. Without checking that the molecule is conceivable, it suggests
C10 H52 N3 O15 which matches slightly better, but cannot be a classical molecule”

Give it a try with your HRMS!

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