Question 1

Which of the following statements best describes the stereochemistry of bromine addition to cyclopentene?

Accepted Answer

The addition is exclusively trans, resulting in trans-1,2-dibromocyclopentane.

Question 2

What is the intermediate formed during the addition of Br$$_2 to an $$alkene?

Accepted Answer

A bromonium ion intermediate

Question 3

Why does the addition of Br$$_2 to $$cyclohexene result in a racemic mixture of trans-1,2-dibromocyclohexane?

Accepted Answer

Because the bromonium ion intermediate allows attack from either side, leading to enantiomers.

Question 4

Which reagent is commonly used for the epoxidation of alkenes?

Accepted Answer

meta-Chloroperoxybenzoic acid (mCPBA)

Question 5

In the hydroboration-oxidation of alkenes, what is the orientation of the addition?

Accepted Answer

Anti-Markovnikov orientation with syn stereochemistry

Question 6

Which of the following best explains Markovnikov's rule in the addition of HX to alkenes?

Accepted Answer

The hydrogen adds to the carbon with the most hydrogens, and the halide adds to the more substituted carbon.

Question 7

What is the major product when HBr is added to 2-methylpropene?

Accepted Answer

2-bromo-2-methylpropane

Question 8

Which of the following is true about the mechanism of halohydrin formation from alkenes?

Accepted Answer

Water attacks the bromonium ion intermediate, leading to anti addition.

Question 9

During the addition of Br$$_2 to an $$alkene, what causes the anti addition stereochemistry?

Accepted Answer

The bromide ion attacks from the side opposite to the bromonium ion, leading to anti addition.

Question 10

Which of the following statements about catalytic hydrogenation of alkenes is correct?

Accepted Answer

The addition of hydrogen is syn and occurs on the same face of the alkene.

Question 11

What is the role of the bromonium ion in the addition of Br$$_2 to an $$alkene?

Accepted Answer

It acts as a reactive electrophile, allowing nucleophilic attack by Br$$^-.$$

Question 12

Which of the following is NOT a product of alkene reactions with electrophiles?

Accepted Answer

Aromatic compound

Question 13

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

Accepted Answer

1,2-Dichloroethane

Question 14

Which of the following best describes the regioselectivity of halohydrin formation from an unsymmetrical alkene?

Accepted Answer

OH adds to the more substituted carbon of the double bond, similar to Markovnikov's rule.

Question 15

Which statement is true about the addition of water to alkenes via oxymercuration?

Accepted Answer

It proceeds via a mercurinium ion intermediate and follows Markovnikov orientation.

Question 16

What is the product of the oxidation of an alkene with potassium permanganate (KMnO$$_4) $$under vigorous conditions?

Accepted Answer

Carboxylic acids and/or carbon dioxide

Question 17

Which of the following is a reason for anti-Markovnikov orientation in hydroboration of alkenes?

Accepted Answer

The transition state is less crowded when boron approaches the terminal carbon.

Question 18

Which of the following is true about the stereochemistry of epoxidation of alkenes?

Accepted Answer

The addition is syn, resulting in a cyclic ether with oxygen.

Question 19

What is the expected product when 1-methylcyclopentene undergoes hydroboration-oxidation?

Accepted Answer

trans-2-Methylcyclopentanol

Question 20

Which statement best describes the role of osmium tetroxide in alkene oxidation?

Accepted Answer

It converts alkenes to syn-diols via cyclic osmate di-ester intermediates.

Electrophilic Addition Mechanisms to Alkenes: Organic Chemistry Study Notes

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