Exam 28: Pericyclic Reactions

Is the thermal [4+2] cycloaddition between allylanion and ethylene an allowed one? To answer, draw the HOMO of allyl anion and the LUMO of ethylene, and comment on the symmetry match of the two.

Which of the following best explains the rearrangement when provitamin D₃ rearranges to vitamin D₃?

Which of the following ring formations must involve a suprafacial bond formation?

Describe a cycloaddition reaction.

Provide the major organic product of the following Diels-Alder cycloaddition.

Which of the following statements best describes the theory of Conservation of Orbital Symmetry?

What is the major product from the following rearrangement?

Draw the structure of the major organic product of the following reaction. Is the product chiral or achiral?

Under photochemical conditions, (2E,4E)-hexadiene undergoes a ________ ring closure to yield ________.

Give the product for the following [3,3] sigmatropic rearrangement.

Which of the following statements best describes what is meant by pericyclic reactions?

When an allyl anion undergoes a cycloaddition under thermal conditions with ethylene (bonds forming at the ends of the π-systems), the cycloaddition is described as ________.

Give the product for the following reaction.

Show the mechanism for each of the following pericyclic reactions.

What is the major product of the following reaction?

How many electrons are present in the nonbonding π molecular orbital of the allyl anion?

Provide the major organic product of the following Diels-Alder cycloaddition.

Which of the following statements concerning electrocyclic reactions is (are)correct?

Under thermal conditions, (2E,4Z)-hexadiene undergoes a ________ ring closure to yield ________.

What is meant by frontier orbitals?