Why is 2-methylpropene less in energy than its alkene counterparts?

Question

Other isomers include 1-butene, cis 2-butene, and trans 2-butene. Why would 2-methylpropene be less in energy if there is more steric hindrance?

Answer 1

Short answer: Look in your textbook index and look up "hyperconjugation", there should be a picture... This is the explanation for the order of stability of alkenes, more substituted being more stable.