Question 1

Which statement best explains why non-polar $$\pi-$$bonds in alkenes typically react with electrophiles rather than nucleophiles?

Accepted Answer

The electron density in the $$\pi-$$bond (HOMO) repels nucleophiles, making electrophilic attack more favorable.

Question 2

According to the molecular orbital diagram for a $$\pi-$$bond, what is the effect of hyperconjugation on the energy of the HOMO?

Accepted Answer

Hyperconjugation raises the energy of the HOMO, increasing the nucleophilicity of the alkene.

Question 3

Which alkene would react fastest with $$m-$$CPBA in an epoxidation reaction, based on the rates shown in the image?

Accepted Answer

Isobutene

Question 4

When the following compound is treated with HBr, which type of rearrangement is most likely to occur during the reaction mechanism?

Accepted Answer

1,2-Methyl shift

Question 5

In the reaction of 4-phenyl-1-butene with HCl, what is the major product and why?

Accepted Answer

The chloride adds to the benzylic position due to carbocation rearrangement and resonance stabilization.

Question 6

Which of the following statements about retrosynthetic analysis is correct?

Accepted Answer

It involves breaking a bond in the target molecule to generate synthons, which are then matched to synthetic equivalents.

Question 7

Which of the following alkenes would produce the given bromoalkane without any carbocation rearrangement when treated with HBr?

Accepted Answer

An alkene with a secondary carbon adjacent to the double bond.

Question 8

Which product is expected when 2,3-dimethyl-2-butene is treated with excess HCl?

Accepted Answer

A dichloride with both chlorines on the same carbon.

Question 9

What is the stereochemical relationship between the two bromine atoms in the product when cyclohexene is treated with $$Br_2$$?

Accepted Answer

They are on opposite sides (anti addition).

Question 10

In the reaction of 2-methyl-2-butene with $$Cl_2 in$$ $$H_2O$$, what is the major product and why?

Accepted Answer

A halohydrin with the OH on the more substituted carbon due to Markovnikov addition.

Question 11

Which of the following best describes the mechanism of oxymercuration-demercuration?

Accepted Answer

It proceeds via a cyclic mercurinium ion intermediate, preventing rearrangements.

Question 12

Which reagent is used to achieve anti-Markovnikov hydration of an alkene?

Accepted Answer

$$B_2H_6$$, followed by $$H_2O_2$$, $$NaOH$$

Question 13

What is the key feature of the hydroboration-oxidation mechanism that leads to syn addition?

Accepted Answer

The addition of B and H occurs in a concerted, four-membered transition state.

Question 14

Which of the following statements about epoxidation of alkenes with peroxyacids is correct?

Accepted Answer

The reaction is stereospecific and preserves the stereochemistry of the alkene.

Question 15

When an epoxide is opened under acidic conditions, where does the nucleophile attack?

Accepted Answer

At the more substituted carbon due to carbocation stabilization.

Question 16

Which of the following best describes a carbene?

Accepted Answer

A carbon atom with two bonds, a lone pair, and a sextet of electrons.

Question 17

Which method generates a carbene for cyclopropanation?

Accepted Answer

Reaction of diazomethane ($$CH_2N_2) $$with light.

Question 18

Which of the following is a pericyclic reaction involving a carbene?

Accepted Answer

Cyclopropanation of an alkene with a carbene.

Question 19

Which of the following best explains why more substituted alkenes are both more stable and more nucleophilic?

Accepted Answer

Hyperconjugation raises the energy of the HOMO, increasing nucleophilicity, while conjugation with $$\sigma-$$bonds stabilizes the alkene.

Reactions of Non-Polar π-Systems - Module 2

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