Question 1

Which pericyclic reaction is involved in the first synthetic step of the Reserpine synthesis shown in the provided scheme?

Accepted Answer

Diels-Alder cycloaddition

Question 2

In the Reserpine synthesis, what is the role of Al(OiPr)3 in the transformation of the intermediate compound?

Accepted Answer

It promotes the selective reduction of the ester group.

Question 3

Which orbital symmetry rule explains the thermal conversion of Precalciferol to Lumisterol and Tachysterol?

Accepted Answer

Woodward-Hoffmann rules

Question 4

In the Precalciferol photochemistry, what is the significance of the HOMO and excited state HOMO diagrams shown?

Accepted Answer

They illustrate the allowed and forbidden transitions based on orbital symmetry.

Question 5

During the Reserpine synthesis, a bromination step is shown. Which reagent is used for this transformation?

Accepted Answer

Br2

Question 6

Which of the following best describes the mechanism of the Diels-Alder reaction in the Reserpine synthesis?

Accepted Answer

Concerted cycloaddition involving a diene and a dienophile

Question 7

In the Precalciferol chemistry, what is the product formed after photochemical ring opening?

Accepted Answer

Pyrocalciferol

Question 8

Which step in the Reserpine synthesis involves a nucleophilic substitution mechanism?

Accepted Answer

Methanolysis with MeONa/MeOH

Question 9

What is the major product when Precalciferol undergoes thermal rearrangement?

Accepted Answer

Lumisterol

Question 10

Which of the following best describes the orbital interaction in the photochemical transformation of Precalciferol?

Accepted Answer

Suprafacial-suprafacial interaction of the excited state HOMO

Question 11

In the Reserpine synthesis, which intermediate is formed after the Diels-Alder reaction and subsequent decarboxylation?

Accepted Answer

A bicyclic ketone

Question 12

Which pericyclic reaction is responsible for the conversion of Precalciferol to Tachysterol under thermal conditions?

Accepted Answer

Electrocyclic ring opening

Question 13

What is the effect of light (hv) on the Precalciferol molecule according to the provided scheme?

Accepted Answer

It induces a photochemical electrocyclic ring opening.

Question 14

Which of the following is a key feature of the endo transition state (endo-TS) in the Diels-Alder reaction shown in the Reserpine synthesis?

Accepted Answer

Maximal overlap of secondary orbitals leading to increased stereoselectivity

Question 15

Which reagent is used to selectively brominate the methyl group in the Reserpine synthesis?

Accepted Answer

NBS (N-Bromosuccinimide)

Question 16

In the Precalciferol chemistry, what is the significance of the number of nodes in the HOMO and excited state HOMO diagrams?

Accepted Answer

They determine the allowedness of pericyclic reactions according to orbital symmetry.

Question 17

Which transformation in the Reserpine synthesis is an example of a pericyclic reaction?

Accepted Answer

Diels-Alder cycloaddition

Question 18

What is the product of the photochemical reaction of Precalciferol as shown in the scheme?

Accepted Answer

Pyrocalciferol

Question 19

Which step in the Reserpine synthesis involves the use of NBS and H2SO4 (aq)?

Accepted Answer

Selective bromination of the methyl group

Question 20

According to the Woodward-Hoffmann rules, which pericyclic reaction is thermally allowed for Precalciferol?

Accepted Answer

Electrocyclic ring opening with suprafacial topology

Pericyclic Reactions: Applications in Reserpine Synthesis and Precalciferol Chemistry

Study Guide - Practice Questions