[Serenagreene]

I really never used a Mass spec for anything other than determining the mass and seeing if there is an odd number of N, or Br or Cl.  I am taking Chemical Synthesis and some homework assigned by the professor who is doing the inorganic side of synthesis is to determine the structure of a molecule using only its mass spec.

Data:

Mass       Intensity
45           471
49           830
51           403
59           111
73           678
75           342
78           623
84           337
86           169
96            18
103           17
119           21
125           27
133         252
134           17
142            7
147            3
149            4
177           11
179             5
191            66
193           133
207           158
208              9
209              5
249             25
251              8
265             59
266              3
267              8
281         1000
282           224
283           118

Because I have an odd MW (281)  I now I have an odd number of N.  I don't think there is any Cl or Br.  I'm hoping that the only atoms in the molecule or C, H, N and O.

Now I'm a little confused, but I thought that mass spec was supposed to give "nested" segments.  Which means I should be able to piece together the original molecule based on the fragments.

So 281 = 84+75+73+49 (using the smallest fragments possible)
I can use the other fragments to build all the other fragments found, with the exception of 78, 177, 249, 251??

So how do I go about figuring what the fragments are?

Thanks,

-Serena