Mass spec

[destain]

Isn't the last peak on a mass spec graph the Mr, but sometimes theres a little peak after the Mr and apparently it's the isotope or something like that, so if we are given a mass spec graph and asked to find the m/e or Mr, how would we know which one to take? the last peak or the second last peak...

[soccerboi]

Ignore that little tiny peak at the end, go with the larger peak before that little peak

[destain]

is it always like that? is the little peak at the end NEVER the parent molecular ion??

[soccerboi]

I think so, i just remember at a lecture i went to, the chief examiner said something about ignoring the little peak that appeared at the end.

[destain]

ahhh okay thanks

and in stav 2008 at the end...theres questions about Distinguised between each of the following pairs of compounds...

e.g Butan-1-ol and Butanoic acid

Answer: Add NaOH as butanol will not react but butanoic acid will react and a gas will be given off. *equation*

And there are 3 other questions like that...Do we need to know this>

[leejieun94]

The smaller peak is due to isotopic effects, d/w abt it

[halfbloodprincess]

ahhh okay thanks

and in stav 2008 at the end...theres questions about Distinguised between each of the following pairs of compounds...

e.g Butan-1-ol and Butanoic acid

Answer: Add NaOH as butanol will not react but butanoic acid will react and a gas will be given off. *equation*

And there are 3 other questions like that...Do we need to know this>

Butanoic acid is an acid so it will react with a base (NaOH), but butan-1-ol won't.

[destain]

yeah but do we need to know a lot of this sort of stuff? it had three others like this adding this to reaact with that..