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

Title: Mass spectre of benzocaine
Post 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 p-aminobenzoate, 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.
Title: Re: Mass spectre of benzocaine
Post by: Borek on December 17, 2006, 03:50:39 PM
So far I found out that the group between 150 and 165 have to be the CH3.

??? What is mass of CH3?
Title: Re: Mass spectre of benzocaine
Post by: Weekend on December 17, 2006, 03:51:38 PM
So far I found out that the group between 150 and 165 have to be the CH3.

??? What is mass of CH3?

Wouldn't that be 15? 12 for Carbon and 3 for each H...
Title: Re: Mass spectre of benzocaine
Post by: Borek on December 17, 2006, 04:05:41 PM
So if its mass is 15, how the mass/charge ratio can reach 150?
Title: Re: Mass spectre of benzocaine
Post by: chiralic on December 17, 2006, 04:15:06 PM
Hi Weekend!

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

Chiralic
Title: Re: Mass spectre of benzocaine
Post by: Weekend on December 17, 2006, 04:18:41 PM
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
Title: Re: Mass spectre of benzocaine
Post by: Weekend on December 17, 2006, 04:23:57 PM
And thank you chiralic it helped a bit :)
Title: Re: Mass spectre of benzocaine
Post by: Borek on December 17, 2006, 04:30:05 PM
So the 150 peak corresponds to benzocaine minus CH3, not to CH3.
Title: Re: Mass spectre of benzocaine
Post by: Weekend on December 17, 2006, 04:30:59 PM
So the 150 peak corresponds to benzocaine minus CH3, not to CH3.

Exactly
Title: Re: Mass spectre of benzocaine
Post by: Weekend on December 17, 2006, 04:31:29 PM
So I'm trying to find out what the rest of the peaks are corresponding to
Title: Re: Mass spectre of benzocaine
Post by: Yggdrasil on December 17, 2006, 05:38:02 PM
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.
Title: Re: Mass spectre of benzocaine
Post by: chiralic on December 17, 2006, 11:28:34 PM
Check McLafferty Rearrangement for Aromatic Ester ...and check fragmentation for Aromatic Amine (look at on m/e 65, 66, 92 and 93)