1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Determining compound from IR and mass spec

  1. Jun 11, 2010 #1
    Using the IR full scan, I have to determine the formula and the structure of the compound. I have attached the scans. Looking at the IR scan, I see that I have an NH and a CH. So is my compound CH2N??

    I also have a mass spec output for an unknown organic compound. I have to determine the structure and formula. Using the CxHy rule, I have the following:

    42= C3H6
    50= C4H2
    67= C5H7
    81= C6H9
    93= C7H9
    107= C8H10
    138= C11H6

    I am not sure what to do after this...do I just write the formulas together and that is my answer??
     

    Attached Files:

    • c.jpg
      c.jpg
      File size:
      14.9 KB
      Views:
      158
    • m.jpg
      m.jpg
      File size:
      24.5 KB
      Views:
      137
    • i.jpg
      i.jpg
      File size:
      6.9 KB
      Views:
      115
  2. jcsd
  3. Jun 11, 2010 #2
    Start by looking at this, as it seems that you lack some fundmental knowledge about how mass spec works. http://www.cem.msu.edu/~reusch/VirtualText/Spectrpy/MassSpec/masspec1.htm"
     
    Last edited by a moderator: Apr 25, 2017
  4. Jun 12, 2010 #3
    ok so i went to the link and i still think i did everything right. what am i doing wrong?? :(
     
  5. Jun 13, 2010 #4
    Hi mimibajiduh, I looked at the spectra and they seem peculiar. Do they correspong to the same compound or to two different ones?
     
  6. Jun 13, 2010 #5
    It is definite that the mass spectrum gives clue that the compound contains bromine - it follows from the fact that in nature Br is represented by two isotopes Br-79 and Br-81 respectively in almost 50:50 abundance (thus its averaged molar mass given in Periodic Table is 79,9). So if a substance contains one Br atom in its mass spectrum some of the peaks will go in pairs of pretty the same intensity and separated by 2 m/z units - just what you have at 81, 93, 107 and 138 (these correspond to molecules containing Br-81). The mass of molecule without a Br atom would then be 138-81=57 wuala! It is just what as we have in the spectrum :).
     
  7. Jun 15, 2010 #6
    oh sorry for not mentioning it in my original post, they are two different ones.
     
  8. Jun 16, 2010 #7
    Well it is kind of impossible to guess the structures then - see yourself: IR spectrum only gives us information about functional groups in the compound 1 and we can say that it has either NH or OH group (both give a broad peak at 3500-3000 cm-1) and from mass spectrum of the compound 2 we can say that it contains one Br atom and that is all. I hardly believe that there are people in the world who could tell what are these compound basing on spectra you give, but good luck anyway ))
     
  9. Jun 16, 2010 #8
    i have attached 2 more scans of the rest of the info i have for the IR. i dont know if it will help or not.
     

    Attached Files:

    • h.jpg
      h.jpg
      File size:
      11 KB
      Views:
      111
    • e.jpg
      e.jpg
      File size:
      12.7 KB
      Views:
      108
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Determining compound from IR and mass spec
  1. Mass Spec (Replies: 2)

Loading...