heat of hydrogenation

Discussion in 'DAT Discussions' started by drzakisadiq, Jul 20, 2008.

  1. SDN is made possible through member donations, sponsorships, and our volunteers. Learn about SDN's nonprofit mission.
  1. drzakisadiq

    drzakisadiq 2+ Year Member

    107
    0
    Jun 30, 2008
    Earlier I posted a thread saying that the more exothermic the heat of hydrogenation, the more stabe it is, and I just wanted to post that I was wrong on that one...

    Correct Part:
    Heat of hydrogenation is the energy released when a pi bond is converted to a sigma bond by the addition of hydrogen. The greater the heat of hydrogenation, the greater the potential energy it has. More potential energy means less stability. Therefore, the least stable molecule will release the most energy upon hydrogenation. THE MORE EXOTHERMIC, THE LESS STABLE.
     
  2. SDN Members don't see this ad. About the ads.
  3. nzaads

    nzaads 7+ Year Member

    16
    0
    Jul 22, 2008
    how do you determine what has the greatest heat of hydrogenation when you are given various alkenes?
     
  4. td4azklz

    td4azklz 2+ Year Member

    198
    0
    Aug 20, 2007
    Richmond, VA
    yeah, how do you determine?
     
  5. alanan84

    alanan84 D1 5+ Year Member

    1,387
    4
    Mar 17, 2008
    You would look at where the double bonds are in relation to each other. Cumulated double bonds are the least stable (highest heat of hydrogenation) and conjugated double bonds are the most stable. (lowest heat of hydrogenation) Isolated bonds are in the middle.
     
  6. alanan84

    alanan84 D1 5+ Year Member

    1,387
    4
    Mar 17, 2008
    Also, terminal double or triple bonds are less stable then internal double or triple bonds.
     
  7. td4azklz

    td4azklz 2+ Year Member

    198
    0
    Aug 20, 2007
    Richmond, VA
    wWhat are cumulated bonds?
     
  8. alanan84

    alanan84 D1 5+ Year Member

    1,387
    4
    Mar 17, 2008
    Double bonds right next to each other.
     
  9. td4azklz

    td4azklz 2+ Year Member

    198
    0
    Aug 20, 2007
    Richmond, VA

    Ok, thanks!
     
  10. Ibraiz

    Ibraiz

    209
    0
    Feb 23, 2010
    Texas
    That means cis will have a higher heat of hydrogenation than trans as cis is less stable than trans. Am I correct?
     
  11. PreDental88

    PreDental88 2+ Year Member

    84
    0
    Dec 28, 2008
    Yup
     

Share This Page