The Diels-Alder reaction modifies conjugated systems in which these alternate in a ring, often inducing resonance.
Allylic rearrangement occurs when an SN1 substitution shifts the position of this structure, which is forbidden at bridgeheads of ring systems according to Bredt's rule. The Diels-Alder reaction modifies conjugated systems in which these alternate in a ring, often inducing resonance. They are responsible for cis-trans isomerism, and they are formed from overlapping p-orbitals creating a (*) sigma and pi bond. At least one of these is present in an alkene [read "al-keen"], making it unsaturated, and they are the only bonds present in diatomic oxygen. For ten points, identify this covalent bond indicated by two lines on a Lewis dot diagram.
Allylic rearrangement occurs when an SN1 substitution shifts the position of this structure, which is forbidden at bridgeheads of ring systems according to Bredt's rule.
double bond [prompt on partial; prompt on "covalent bond;" do NOT accept any other type]