Dismiss Notice
Hey Guest! Check out the 3 MCAT Study Plan Options listed in the 'stickies' area at the top of the forums (BoomBoom, SN2ed, and MCATJelly). Let us know which you like best.

Also, we now offer a MCAT Test-Prep Exhibitions Forum where you can ask questions directly from the test-prep services.
Dismiss Notice
SDN members see fewer ads and full resolution images. Join our non-profit community!

help with simple orgo question

Discussion in 'MCAT Discussions' started by ankit1ag, Apr 9, 2007.

  1. ankit1ag

    Joined:
    Mar 2, 2007
    Messages:
    40
    Likes Received:
    1
    Status:
    Pre-Medical
    Can someone help me with this question:

    -how is C-5 a chiral carbon. It is not bonded to four diff subst. because of the 4 & 6 CH2 groups. And tell me why 2 & 7 are not chiral. Is it because they are only bonded to 3 subst.?

    Carvone is shown below with certain carbon atoms labeled.


    [​IMG]

    (+)-Carvone and (–)-carvone differ in the orientations of the substituents around which of the following carbon atoms?


    A) Carbon 2 only
    B) Carbon 5 only
    Ex:Carbon 5 is the only stereogenic carbon atom (chirality center); carbons 2 and 7 are not stereocenters. Thus, answer choice B is the best answer.


    C) Carbons 2 and 5 only
    C) Carbons 2, 5, and 7 only
     
  2. Thread continues after this sponsor message. SDN Members do not see this ad.

  3. HippocratesX

    HippocratesX Member

    Joined:
    Mar 22, 2002
    Messages:
    292
    Likes Received:
    1
    Since it is a ring structure, you have to treat each side of the carbon that you are looking at like a substituent...so even though there are 2 CH2 groups, like you said, if you continute following the molecule on each side, they are different. The right side of carvone has a carbonyl group (C=O) and the left side does not, so that makes them 2 different substituents, which makes the carbon chiral. If this were NOT a ring structure and it was linear, then you are right, it would not be a chiral molecule.

    so one of the substituents on the right side would be CH2-C=O and the other side would be CH2-CH-CH3. ANd the other 2 substituents for this chiral carbon would be a Hydrogen which is not shown, and the C-CH2-CH3 group hanging below.
     

Share This Page