2-carene and 3-carene

[juicyFruit]

So I have the two spectra for these molecules. They are fairly the same except for the peak of m/z 121, which is a m-15 peak...meaning it loses a methyl group...or at least that is my assumption. What I don't understand is why it is a strong peak for 2-carene and a weak peak for 3-carene. Any advice would be appreciated!

[NATHANALANPATRICKROGERS]

Originally Posted by juicyFruit

So I have the two spectra for these molecules. They are fairly the same except for the peak of m/z 121, which is a m-15 peak...meaning it loses a methyl group...or at least that is my assumption. What I don't understand is why it is a strong peak for 2-carene and a weak peak for 3-carene. Any advice would be appreciated!

2-carene

3,7,7-Trimethylbicyclo[4.1.0]hept-2-ene
--
3-carene

3,7,7-Trimethylbicyclo[4.1.0]hept-3-ene

1. check lot no's - synthetic routes may differ
2. check reagent stability of 2 -vs- 3-carene
3. assume the m=15 is something other than CH3
4. assume the position of the double-bond is significant
5. perform an accurate net-sum comparison of peaks
6. perform instrument maintenance and test for bias

[juicyFruit]

Well I tried the Reverse-Diels Adler mechanism on the two...and it doesn't work for the 2-carene...is that what you mean by assumnig the position of the double-bond is significant? I am not sure what that tells you about the 121 peak . The m-15 peak has to be a methyl group loss...unless you lose 15 H's??