Question 1

Which rearrangement is involved in the conversion of cyclohexanone oxime to caprolactam under acidic conditions, as shown in Practice Problem 1?

Accepted Answer

Beckmann rearrangement

Question 2

In the Beckmann rearrangement, which group migrates during the rearrangement step?

Accepted Answer

The group anti to the leaving group

Question 3

Practice Problem 2 involves the conversion of a methyl ketone to an isoquinoline derivative. Which intermediate is formed after the reaction with hydroxylamine?

Accepted Answer

An oxime

Question 4

In the Staudinger reaction (Practice Problem 3), what is the role of triphenylphosphine ($$\mathrm{$$PPh_3$$}$$)?

Accepted Answer

It reduces the azide to an iminophosphorane

Question 5

Which reagent is used as a hypervalent iodine(III) oxidant in Practice Problem 4?

Accepted Answer

PIFA ($$\mathrm{PhI($$OCOCF_3$$)_2})$$

Question 6

In Practice Problem 5, the rearrangement of an azide in the presence of $$t-$$BuOH leads to the formation of which functional group in the product?

Accepted Answer

Carbamate

Question 7

The reaction sequence in Practice Problem 6 involves the conversion of an ester to an amine via a rearrangement. Which rearrangement is this?

Accepted Answer

Lossen rearrangement

Question 8

In Practice Problem 7, irradiation with light ($$hv) $$initiates a rearrangement of a diazo compound in methanol. What is the key intermediate formed after nitrogen loss?

Accepted Answer

A carbene

Question 9

Practice Problem 8 shows a rearrangement of a diazo compound in the presence of methanol. What is the driving force for the rearrangement?

Accepted Answer

Loss of nitrogen gas ($$N_2)$$

Question 10

In Practice Problem 9, NBS (N-bromosuccinimide) is used to brominate a compound. What is the next key transformation after bromination?

Accepted Answer

Staudinger reaction with $$\mathrm{$$PPh_3$$}$$

Question 11

In Practice Problem 10, the use of LDA (lithium diisopropylamide) at $$0^\circC $$leads to which type of rearrangement?

Accepted Answer

Brook rearrangement

Question 12

Which of the following best describes the mechanism of the rearrangement in Practice Problem 11, where an arylamine reacts with a tosylated imide?

Accepted Answer

Aza-analogue of the Lossen rearrangement

Question 13

A student attempts the Beckmann rearrangement of cyclohexanone oxime but obtains a low yield of caprolactam. Which of the following is the most likely reason?

Accepted Answer

The reaction was performed under basic conditions

Question 14

In the Staudinger reaction, which byproduct is formed along with the amine?

Accepted Answer

$$\mathrm{PPh_3O} ($$triphenylphosphine oxide)

Question 15

Which of the following is a key feature of the Lossen rearrangement mechanism?

Accepted Answer

Migration of an alkyl group from carbon to nitrogen

Question 16

A chemist uses PIFA ($$\mathrm{PhI($$OCOCF_3$$)_2}) in a $$reaction with an amide and observes a rearrangement. What is the role of PIFA in this transformation?

Accepted Answer

It acts as an oxidizing agent

Question 17

In the photochemical rearrangement of a diazo compound (Practice Problem 7), which solvent is crucial for trapping the carbene intermediate?

Accepted Answer

Methanol

Question 18

Which of the following best explains why nitrogen gas ($$N_2) $$loss is a common driving force in rearrangement reactions involving azides and diazo compounds?

Accepted Answer

Loss of $$N_2 is $$entropically favorable and provides a strong thermodynamic driving force

Question 19

A student is asked to design a synthesis of a primary amine from an ester using a rearrangement. Which sequence of reagents would be most appropriate?

Accepted Answer

1. $$\mathrm{NH_3$}$$, 2. $$\mathrm{Br_2$}$$, $$\mathrm{NaOH}$$

Question 20

In the Brook rearrangement (Practice Problem 10), what is the key step that distinguishes it from other rearrangements?

Accepted Answer

Migration of a silyl group from carbon to oxygen

Organic Chemistry II: Rearrangement Reactions – Practice Problems and Mechanisms

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