Basically, I suck at mass spectrometry, I don't understand about m/z values and m+ ions etc. and the textbook doesn't help at all!
Please can some smart person explain it to me?
Thank you x
OCR A doesn't worry about M+ peaks.
Often, they ask about the base peak (or a named peak). You have to be able to work out an ion that has the Mr the same as the base peak. Drawing the structure of said ion, with the charge in the correct place, is not something I can do over the Interwebs.
One the furthest to the right gives Mr or the molecule you are looking it
Other peaks give parts of that molecule
Always right them with a '+' as they are IONS. There is always a mark for just writing the mr with a + sign next to it.
If you see a tiny little peak on the very right hand side, ignore it. It's irrelevant. ( usually has a height of 1)
You have to be patient and play around to try and find the structure of your molecule but if you subtract the Ar of each atom as you build it onto your molecule from your peak value you will see if you're on the right track or not... eg an m/z peak at 30... put two carbons down on your page and then draw on your 6 hydrogens ( subtract 24 then subtract 6 and you will soon see youve got the right molecule)
Quite often you will be given a infrared spectroscopy bit with the question too...use this it's essential.
Google 'common fragment ions a level' and you might be able to remember a few of the structures but it's not essential as you can work it out with a bit of thought and time in the exam.
check this site out....http://www.chemguide.co.uk/analysis/masspecmenu.html
aooo then says suggestion for formula of m/z peak at 29
I started off with 2 carbons and 6 hydrogens (ethane) and realised the masses of those gave me 30 not 29. So just take a hydrogen off and hey presto 29... (Dont forget to put a plus sign after as once again it is a fragment ION)
Hope all of this helps
Just treat it all as a puzzle, dont over complicate it... Possibly some of the easier stuff in the paper as it gives you all the info you need to know and the maths is just addition and subtraction