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!

Mass Spec- breaking the benzene ring

  1. Mar 23, 2010 #1
    1. The problem statement, all variables and given/known data
    the molecular formula of the compound under analysis is C8H8O2 = Mr of 136
    the mass spectrum shows the peak at 91 to be the most stable. I'm supposed to obtain structures representing the peak at 91 as well as at 118 and 65


    3. The attempt at a solution

    I represented 91 as the benzene ring with H-C(-H) attached

    @ 118 H-C-C(=O) is attached

    I'm having trouble getting the structure at 65

    C8H8O2 would be represented as the benzene ring with H-C(-H)-C(=O)-O-H attached.
    The only way i'm seeing to obtain 65 is if i remove the attached group from C8H8O2 along with a C from the benzene ring. Is this even possible? Because I know the benzene ring is very stable...:confused:
     
  2. jcsd
  3. Mar 24, 2010 #2
    Are you positive this compound contains a benzene ring?

    Could it be a cyclopentadiene or fulvene derivative?
     
  4. Mar 24, 2010 #3
    well...those groups aren't on the syllabus I'm studying. Benzene and phenol are the only aromatic compounds I'm studying. Can benzene be an option?
     
  5. Mar 25, 2010 #4

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It's not benzene anymore... it's tropylium (m=91).
     
  6. Mar 29, 2010 #5
    I don't understand:confused:

    maybe i explained it wrong? i was trying to describe the structure i assumed the fragments to be. But what I'm not clear on is if it's ever possible to break the benzene ring. I know the ring is stable due to the delocalised electrons...so I don't understand why the benzene ring itself would fragment. I have no idea as to what other solution it could be. :redface:
     
  7. Mar 30, 2010 #6

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    That's why I gave you a hint... tropylium ion. Very interesting fragmentary pattern for tropylium ion... nuff said.

    See above.

    hint: google "tropylium fragmentary pattern"
     
  8. Apr 11, 2010 #7
    thank you!
     
  9. Apr 11, 2010 #8

    chemisttree

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    De nada!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Mass Spec- breaking the benzene ring
  1. Mass Spec (Replies: 2)

Loading...