Question 1

Which of the following statements best describes a saturated hydrocarbon?

Accepted Answer

It contains only single bonds between carbon atoms.

Question 2

What is the main reason alkanes are generally unreactive?

Accepted Answer

They have strong sigma bonds and atoms with no partial charge.

Question 3

Which of the following correctly represents homolytic bond cleavage?

Accepted Answer

$$A-B \rightarrow A$$^{\cdot}$$ + B$$^{\cdot}$$

Question 4

During the monochlorination of methane, which species is formed in the propagation step?

Accepted Answer

Methyl radical ($$\cdot CH_3$)

Question 5

Why is using excess alkane important in a chlorination reaction?

Accepted Answer

It minimizes the formation of dihalogenated and trihalogenated products.

Question 6

Which of the following statements about the selectivity of bromination versus chlorination is correct?

Accepted Answer

Bromine radical is less reactive and more selective than chlorine radical.

Question 7

Which radical is the most stable among the following?

Accepted Answer

Tertiary alkyl radical

Question 8

What is the major product when 2-bromobutane is formed by bromination of butane?

Accepted Answer

2-bromobutane

Question 9

Which of the following best explains why peroxide causes bromine to be the electrophile in the addition of HBr to alkenes?

Accepted Answer

Peroxide initiates a radical mechanism, reversing the usual Markovnikov selectivity.

Question 10

Why does the peroxide effect occur only with HBr and not with HCl or HI?

Accepted Answer

Both propagation steps for HBr are exothermic, making the radical chain reaction favorable.

Question 11

What is the stereochemical outcome when a new asymmetric center is formed during a radical substitution reaction?

Accepted Answer

A racemic mixture of enantiomers is produced.

Question 12

Which of the following is true about the resonance stabilization of allylic and benzylic radicals?

Accepted Answer

Benzylic radicals have more resonance contributors than allylic radicals.

Question 13

Which reagent is commonly used to brominate allylic carbons without adding to the double bond?

Accepted Answer

N-bromosuccinimide (NBS)

Question 14

What is the expected product when cyclopropane undergoes ring-opening with HBr?

Accepted Answer

1-bromopropane

Question 15

In the mechanism for radical addition of HBr to 1-butene in the presence of peroxide, which product is formed?

Accepted Answer

1-bromobutane

Question 16

Which of the following is a correct propagation step in the radical bromination of ethane?

Accepted Answer

$$CH_3CH_3 + \cdot Br \rightarrow CH_3CH_2\cdot + HBr$$

Question 17

Which of the following best describes the activity-selectivity principle in halogenation?

Accepted Answer

A less reactive halogen is more selective in its reactions.

Question 18

What is the effect of resonance on the stability of allylic and benzylic radicals?

Accepted Answer

Resonance delocalizes the unpaired electron, increasing radical stability.

Question 19

Which of the following is true about the stereochemistry of radical addition reactions forming a new chiral center?

Accepted Answer

Both enantiomers are formed because the radical intermediate is planar.

Radical Reactions of Alkanes: Mechanisms and Selectivity

Study Guide - Practice Questions