In considering relative stability of alkenes, my understanding is that
1. More-substituted alkenes are more stable than less-substituted alkenes,
2. Trans alkenes are more stable than cis alkenes, and
3. Conjugated alkenes are more stable than isolated alkenes.
Given this information, I would say that (in terms of stability), we have
trans-2,5-dimethyl-3-hexene > 2,3-dimethyl-2-hexene > 3-ethyl-3-hexene > 3-methyl-1-heptene.
However, the correct order is
2,3-dimethyl-2-hexene > 3-ethyl-3-hexene > trans-2,5-dimethyl-3-hexene > 3-methyl-1-heptene.
Why is this so?
Thank you.