Deck 28: Pericyclic Reactions

Question 1

Classify the reaction:

A) electrocyclic
B) cycloaddition
C) sigmatropic reaction

Answer 1

A

Question 2

Classify the reaction:

A) electrocyclic
B) cycloaddition
C) sigmatropic reaction

Answer 2

C

Question 3

Classify the reaction:

A) electrocyclic
B) cycloaddition
C) sigmatropic reaction

Answer 3

B

Question 4

Consider the carbocation:
a. How many pi molecular orbitals are there?
b. Classify each MO as symmetric or antisymmetric.
c. Which MOs are bonding and antibonding?
d. Which MOs are the HOMO and LUMO?

Question 5

Sketch the molecular orbitals for 1,3-pentadiene. Fill in the number of electrons in each molecular orbital, then identify the HOMO and LUMO. How many nodes are in each molecular orbital?

Question 6

Without drawing a molecular orbital diagram, consider the structure and identify
a. the number of pi electrons.
b. which molecular orbitals will be occupied.
c. which molecular orbitals are symmetric.
d. which molecular orbital is the HOMO.

Question 7

Given the starting material and conditions, identify the type of pericyclic reaction, the number of electrons involved in the reaction, and draw the major organic product. Clearly show stereochemistry, if applicable.

Question 8

Given the starting material and conditions, identify the type of pericyclic reaction, the number of electrons involved in the reaction, and draw the major organic product. Clearly show stereochemistry, if applicable.

Question 9

Which conditions should you use to perform the reaction and why?

A) heat because the reaction is conrotatory
B) light (h $\nu$ ) because the reaction is conrotatory
C) heat because the reaction is disrotatory
D) light (h $\nu$ ) because the reaction is disrotatory

Question 10

Which conditions should you use to perform the reaction and why?

Question 11

Predict the major organic product and show stereochemistry where relevant.

Question 12

Two ethylene molecules can undergo a [2+2] cycloaddition, but only under photochemical conditions. Explain this difference in reactivity.

Question 13

Given the starting material and conditions, identify the type of pericyclic reaction, the number of electrons involved in the reaction, and draw the major organic product. Clearly show stereochemistry, if applicable.

Question 14

Predict the major organic product for the reaction.

Question 15

Classify the sigmatropic reaction with bracketed numbers.

Question 16

Classify the sigmatropic reaction with bracketed numbers.

Question 17

Given the starting material and conditions, identify the type of pericyclic reaction, the number of electrons involved in the reaction, and draw the major organic product. Clearly show stereochemistry, if applicable.

Question 18

Predict the major organic products in the boxes and show stereochemistry where relevant.

Question 19

Draw curved-arrow mechanism showing how this transformation occurs.

Question 20

Outline a synthesis for this transformation. A key step should be a [2,2] or [4,2] cycloaddition.

Question 21

This transformation can occur through two pericyclic reactions. Outline a synthesis for the transformation.

Question 22

Deduce the starting materials needed to synthesize this compound.

Question 23

Outline a synthetic sequence to give this transformation. Hint: A sigmatropic rearrangement is a key step.

Question 24

Draw a curved-arrow mechanism showing how the alcohol is transformed to the ketone.

Question 25

Give the product for a [1,5] deuterium shift for this structure: