16. Conjugated Systems

c. Under photochemical conditions, will ring closure be conrotatory or disrotatory?

d. Will the product have the cis or the trans configuration?

Explain why the hydrogen and the methyl substituent are trans to one another after photochemical ring closure of provitamin D₃ to form 7-dehydrocholesterol.

Draw the product of each of the following reactions:

c.

d.

Draw the product formed when each of the following compounds undergoes an electrocyclic reaction

b. under photochemical conditions.

1.

2.

Chorismate mutase is an enzyme that promotes a pericyclic reaction by forcing the substrate to assume the conformation needed for the reaction. The product of the pericyclic reaction is prephenate that is subsequently converted into the amino acids phenylalanine and tyrosine. What kind of a pericyclic reaction does chorismate mutase catalyze?

Predict the product of the following electrocyclic reactions.

(c)

Draw the product of each of the following reactions:

d.

Predict the product of the following [2 + 2] cycloadditions.

(b)

Predict the product of the following electrocyclic reactions.

(b)