help with mass spectroscopy please!! :D

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*skye*
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#1
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Hey all you bright ppl out there! hehe

I dont suppose anyone could just run thru the basics of the mass spectrum for me? what ur meant to do with it and to read it and all that stuff?

Im alrite with all the other ones like infra red and nmr but this one always puzzles me for some reason...??

Its an emergency cos I have a mock exam tomoro... and Ive been off skool for weeks so ive missed AN AWFUL LOT OF LESSONS!!! ive got a whole textbook to learn and absorb by tomoro... eek

Thank youuuuuuuuuuuuuu
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Eru Iluvatar
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http://chipo.chem.uic.edu/web1/ocol/spec/MS.htm

http://www.chem.ucalgary.ca/courses/...3/ch13-ms.html

These any good?
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*skye*
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hey, thanks... ive had a look at these sites and i gotta say, im even more confused now... even for the module four chem paper, i didnt realise this was so complex... to be honest, i dont know how i managed to do it?!

could u just sum up

a/ what its meant to show... ie the peaks and things?
b/ how to work out the formula then,
in simple terms, lol? Thanks...





QUOTE=Iluvatar]http://chipo.chem.uic.edu/web1/ocol/spec/MS.htm

http://www.chem.ucalgary.ca/courses/...3/ch13-ms.html

These any good?[/QUOTE]
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Eru Iluvatar
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(Original post by *skye*)
hey, thanks... ive had a look at these sites and i gotta say, im even more confused now... even for the module four chem paper, i didnt realise this was so complex... to be honest, i dont know how i managed to do it?!

could u just sum up

a/ what its meant to show... ie the peaks and things?
b/ how to work out the formula then,
in simple terms, lol? Thanks...





QUOTE=Iluvatar]http://chipo.chem.uic.edu/web1/ocol/spec/MS.htm

http://www.chem.ucalgary.ca/courses/...3/ch13-ms.html

These any good?
[/QUOTE]

To be honest, i don't have a clue about it at all. I just read your post, and looked for stuff on the net that sounded right.
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MadNatSci
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(Original post by *skye*)
hey, thanks... ive had a look at these sites and i gotta say, im even more confused now... even for the module four chem paper, i didnt realise this was so complex... to be honest, i dont know how i managed to do it?!

could u just sum up

a/ what its meant to show... ie the peaks and things?
b/ how to work out the formula then,
in simple terms, lol? Thanks...
I'm assuming a basic knowledge of how the mass spectrometer works, let me know if you need extra info!

When you stick a substance in a mass spectrometer, it gets broken up into random fragments which obviously weigh different amounts according to how big they are. The fragments are positively charged because an electron gets knocked out when they're broken up; they all have the same charge so when they're passed into the magnetic field, the only thing which changes how much they are deflected is their mass. So heavier fragments will get deflected less than lighter ones - this allows you to tell how much each fragment weighs.

The peaks are at points corresponding to the masses of the fragments. The heights of the peaks show how many fragments have been detected at each mass; the peak corresponding to the biggest mass is usually the molecular ion - ie the starting molecule which has only lost an electron. So this gives you the molecular mass of the compound. To work out its formula you need to look at the fragments and work out what atoms are likely to make up the masses - eg fragments weighing in at 15 are likely to be -CH3 groups. You can put this all together if you work out where a molecule is most likely to snap, what all the fragments have to add up to (which as I said, you're given: the mass of the molecular ion), and construct a picture of the molecule. You just have to think about it logically and it helps to draw it. I don't remember them ever just giving me a mass spec and telling me to deduce the structure of the molecule just from that, though - they usually give you other information I think.
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username9816
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What would you know about Science!!! (J/K)
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Ben.S.
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I remember on module 4 (AQA), all that you needed to know about mass spec. where the m/z ratios 15 and 43 from the fragmentation of acetone.

Ben
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MadNatSci
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The exam boards do differ I think - I'm pretty certain Edexcel wanted you to know more than that. We studied it anyway!
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