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.