Turn on thread page Beta
    • Thread Starter
    Offline

    17
    ReputationRep:
    Hi,

    I'm really struggling with labelling the carbon environments of benzophenone. There's 5 peaks in the C NMR spectrum so I think that there's 5 environments but I'm not sure which ones are equivalent.

    Any help would be really appreciated.
    Offline

    19
    (Original post by VioletPhillippo)
    Hi,

    I'm really struggling with labelling the carbon environments of benzophenone. There's 5 peaks in the C NMR spectrum so I think that there's 5 environments but I'm not sure which ones are equivalent.

    Any help would be really appreciated.
    You are looking for symmetry in the molecule: C6H5-(C=O)-C6H5

    The two aromatic groups are equivalent.

    Does that help?
    Offline

    15
    ReputationRep:
    The carbon creating the carbonyl function is one peak (1)

    Then the other 4 come from the phenyl groups.

    1 from the 2 carbons attached to the carbonyl (since the two phenyls are symmetrical)


    2*(1 peak from 2 symmetrical carbons on each phenyl) - (2* since there are 4 symmetrical carbons on each phenyl).

    Symmetry between phenyls also means there are just two environments in these 'middle carbons'

    So there's really twofold symmetry in this case. Symmetry from within each phenyl and symmetry between phenyls.

    One peak from the two remaining carbons on both phenyls - (1 carbon remaining per phenyl, symmetry between phenyls, therefore same environment, therefore one peak).

    Total: 5 peaks.
 
 
 
Poll
Is the Big Bang theory correct?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.