Expected ΔH°_hydrog for allene is −252 kJ/mol. Allene is less stable than a nonconjugated diene, which is less stable than a conjugated diene.

1-Chloro-2-pentene, 3-chloro-1-pentene, 4-chloro-2-pentene

4-Chloro-2-pentene predominates in both.

1,2 Addition: 6-bromo-1,6-dimethylcyclohexene 1,4 Addition: 3-bromo-1,2-dimethylcyclohexene

Interconversion occurs by S_N1 dissociation to a common intermediate cation.

The double bond is more highly substituted.

Good dienophiles: (a), (d)

Compound (a) is s-cis. Compound (c) can rotate to s-cis.

300–600 kJ/mol; UV energy is greater than IR or NMR energy.

1.46 × 10⁻⁵ M

All except (a) have UV absorptions.