
Interpretation:
Only the 2E,4E isomer is obtained in practice by opening of trans-3,4-Dimethylcyclobutene by two conrotatory paths to give symmetry-allowed products either (2E,4E)-2,4-hexadiene or (2Z,4Z)-2,4-hexadiene.
Concept introduction:
An electrocyclic ring-opening reaction is a reaction in which a σ bond of a cyclic reactant is cleaved to form a conjugated product with one more π bond. It occurs only when like phases of orbitals can overlap to form a bond. Such a reaction is symmetry allowed. It cannot occur between orbitals of opposite phase. Such a reaction is symmetry forbidden. To form a bond, the p orbitals on the terminal carbons must rotate so that like phases can interact to form the new sigma bond. Two modes of rotation are possible - When like phases of the p orbitals are on the same side of the molecule, the two orbitals must rotate in opposite direction one clockwise and one counterclockwise. Rotation in opposite directions is said to be disrotatory.
When like phases of the p orbitals are on opposite sides of the molecule, the two orbitals must rotate in the same direction both clockwise or both counterclockwise. Rotation in the same direction is said to be conrotatory.

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Chapter 30 Solutions
Organic Chemistry
- Provide the drawing of the unknown structure that corresponds with this data.arrow_forward20.44 The Diels-Alder reaction is not limited to making six-membered rings with only car- bon atoms. Predict the products of the following reactions that produce rings with atoms other than carbon in them. OCCH OCCH H (b) CH C(CH₂)s COOCH མ་ནས་བ (c) N=C H -0.X- (e) H C=N COOCHS + CH2=CHCH₂ →→arrow_forwardGiven the attached data, provide the drawing for the corresponding structure.arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning

