Question 1

Which of the following best explains why a methyl shift occurs during the reaction of 3,3-dimethyl-1-butene with HCl?

Accepted Answer

To generate a more stable tertiary carbocation from a secondary carbocation.

Question 2

Which product is formed when bromocyclohexane is treated with KOH in ethanol?

Accepted Answer

Cyclohexene

Question 3

What is the stereochemical outcome when cyclopentene reacts with Br$$_2$$?

Accepted Answer

trans-1,2-Dibromocyclopentane is formed exclusively.

Question 4

Which intermediate is responsible for the anti stereochemistry observed in the halogenation of alkenes?

Accepted Answer

Bromonium ion

Question 5

In the laboratory, which reagent is commonly used to generate Br$$_2$$ for halohydrin formation in aqueous DMSO?

Accepted Answer

N-Bromosuccinimide (NBS)

Question 6

Which of the following best describes the Markovnikov rule as it applies to the hydration of alkenes?

Accepted Answer

The hydrogen atom adds to the carbon with more hydrogens, and the OH group adds to the more substituted carbon.

Question 7

What is the major product when ethylene reacts with Cl$$_2$$?

Accepted Answer

1,2-Dichloroethane

Question 8

Which of the following statements about the mechanism of halohydrin formation from an alkene, Br$$_2$$, and H$$_2O is $$correct?

Accepted Answer

Water acts as a nucleophile, opening the bromonium ion intermediate.

Question 9

Which sequence correctly describes the steps in the acid-catalyzed hydration of an alkene?

Accepted Answer

Protonation of the alkene, nucleophilic attack by water, deprotonation to yield alcohol.

Question 10

Which of the following is a key difference between the halogenation and hydration of alkenes?

Accepted Answer

Halogenation forms a dihalide, while hydration forms an alcohol.

Question 11

What is the role of NaBH$$_4 in $$the oxymercuration–demercuration reaction of alkenes?

Accepted Answer

It reduces the organomercury intermediate to yield the alcohol.

Question 12

Which product is formed when 1-methylcyclohexanol is treated with H$$_2SO$_4$$ and H$$_2O at 50$^	ext{o}C$$?

Accepted Answer

1-Methylcyclohexene

Question 13

Which of the following best describes the product of the reaction between styrene, NBS, H$$_2O$$, and DMSO?

Accepted Answer

2-Bromo-1-phenylethanol

Question 14

Which of the following is NOT a possible product from the reactions of alkenes as shown in the reaction map?

Accepted Answer

Aromatic compound

Question 15

In the halogenation of alkenes, why is the anti addition observed?

Accepted Answer

The nucleophile attacks from the side opposite to the halogen bridge in the bromonium ion.

Question 16

Which of the following statements about the oxymercuration–demercuration reaction is correct?

Accepted Answer

It follows Markovnikov’s rule and avoids carbocation rearrangement.

Question 17

Which of the following is the correct order of steps in the formation of a halohydrin from an alkene, Br$$_2$$, and H$$_2O$$?

Accepted Answer

Formation of bromonium ion, nucleophilic attack by water, deprotonation.

Question 18

Which product is formed when 1-methylcyclopentene undergoes oxymercuration–demercuration?

Accepted Answer

1-Methylcyclopentanol

Question 19

Which of the following is a real-world application of the halogenation of alkenes?

Accepted Answer

Production of 1,2-dichloroethane, a precursor to vinyl chloride for PVC manufacturing.

Alkenes: Structure, Reactivity, and Key Reactions

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