Question 1

Which of the following best explains why only chlorination and bromination are commonly used for the radical halogenation of alkanes, and not fluorination or iodination?

Accepted Answer

Fluorine radicals react violently, and iodine radicals are too unreactive to remove a hydrogen atom.

Question 2

During the radical halogenation of propane with bromine under UV light, which product is formed in the greatest amount and why?

Accepted Answer

2-bromopropane, because secondary radicals are more stable than primary radicals.

Question 3

Which of the following statements about the stability of alkyl radicals is correct?

Accepted Answer

Tertiary radicals are the most stable due to hyperconjugation and inductive effects.

Question 4

What is the main reason that radical halogenation of alkanes requires heat or light?

Accepted Answer

To provide energy for the homolytic cleavage of the halogen molecule, generating radicals.

Question 5

Which of the following best describes the propagation steps in the radical chlorination of methane?

Accepted Answer

The steps in which radicals react with non-radical species to form new radicals and products.

Question 6

A student is asked to predict the major product of the reaction: $$CH_3CH_2CH_2CH_3 + Br_2$ \xrightarrow{hv} ?$$ What is the major product and why?

Accepted Answer

2-bromobutane, because bromine selectively abstracts the hydrogen from the most stable (secondary) radical.

Question 7

Which of the following best explains why peroxide affects the addition of HBr to alkenes but not the addition of HCl or HI?

Accepted Answer

Peroxide initiates a radical chain mechanism that is only exothermic for HBr addition.

Question 8

Which of the following best describes the role of N-bromosuccinimide (NBS) in the bromination of allylic and benzylic positions?

Accepted Answer

NBS acts as a radical initiator by generating Br radicals in situ.

Question 9

Which of the following best explains why benzylic and allylic radicals are more stable than tertiary alkyl radicals?

Accepted Answer

They are stabilized by resonance delocalization of the unpaired electron.

Question 10

A radical polymerization is initiated by the homolytic cleavage of a peroxide. Which of the following best describes the propagation step?

Accepted Answer

A radical reacts with a monomer to form a new radical, which continues to react with more monomers.

Question 11

Which of the following is a real-world application of radical chain-growth polymerization?

Accepted Answer

Production of poly(vinyl chloride) (PVC) for plumbing pipes.

Question 12

Which of the following best describes the 'head-to-tail' addition in radical polymerization of monosubstituted ethylenes?

Accepted Answer

The substituent on the monomer is always positioned away from the radical site, leading to a regular polymer structure.

Question 13

Which vitamin is most effective at trapping radicals in nonpolar environments such as cell membranes?

Accepted Answer

Vitamin E (α-tocopherol)

Question 14

In the radical addition of HBr to 1-butene in the presence of peroxide, what is the major product and why?

Accepted Answer

1-bromobutane, because the reaction follows anti-Markovnikov addition due to the radical mechanism.

Question 15

Which of the following best describes the termination step in a radical polymerization reaction?

Accepted Answer

Two radical chains combine to form a non-radical product, ending the chain reaction.

Question 16

Which of the following best explains why bromine is more selective than chlorine in the radical halogenation of alkanes?

Accepted Answer

Bromine radicals are less reactive and therefore more selective for the most stable radical intermediate.

Question 17

Which of the following is the correct order of radical stability from most stable to least stable?

Accepted Answer

Benzylic \u003e Allylic \u003e Tertiary \u003e Secondary \u003e Primary \u003e Vinyl \u003e Methyl

Question 18

Which of the following best describes the difference between homolytic and heterolytic bond cleavage?

Accepted Answer

Homolytic cleavage gives one electron to each atom, forming radicals; heterolytic cleavage gives both electrons to one atom, forming ions.

Question 19

Which of the following best explains why radical halogenation of alkanes is important in organic synthesis?

Accepted Answer

It allows for the selective introduction of halogen atoms at specific positions, enabling further functional group transformations.

Free Radical Chemistry: Mechanisms, Reactivity, and Applications

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