Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Weekend on December 17, 2006, 03:39:46 PM

Hi!
First of all, I'd like to say that I'm new at this forum :). I have a mass spectre of benzocaine (ethyl paminobenzoate, C9H11NO2) I'm trying to analyze which part of the molecule is seperated in each "peak". The spectre can be found at the following URL:
http://img323.imageshack.us/img323/9170/benzocainepx0.gif
So far I found out that the group between 150 and 165 have to be the CH3. So I would be glad, if anyone could help me identify the rest.

So far I found out that the group between 150 and 165 have to be the CH3.
??? What is mass of CH_{3}?

So far I found out that the group between 150 and 165 have to be the CH3.
??? What is mass of CH^{3}?
Wouldn't that be 15? 12 for Carbon and 3 for each H...

So if its mass is 15, how the mass/charge ratio can reach 150?

Hi Weekend!
Read page 3 of this link:
http://www.ru.ac.za/academic/departments/pharmacy/chem/2nds/spectutplus.pdf
Chiralic

So if its mass is 15, how the mass/charge ratio can reach 150?
I understand it like thiis. You have a molecule which has the mass 165, then a part of it is "cut" off, and then the molecule is 150. This means it lost 15 of its mass, which is equal to CH3

And thank you chiralic it helped a bit :)

So the 150 peak corresponds to benzocaine minus CH_{3}, not to CH_{3}.

So the 150 peak corresponds to benzocaine minus CH_{3}, not to CH_{3}.
Exactly

So I'm trying to find out what the rest of the peaks are corresponding to

Since you have a carbonyl, I would expect to see beta cleavage. Also, since there's an aromatic ring, you may see tropyllium ions, which are common in mass spectra of aromatic compounds.

Check McLafferty Rearrangement for Aromatic Ester ...and check fragmentation for Aromatic Amine (look at on m/e 65, 66, 92 and 93)