Q: Which of the following is a correct initiation step for the radical polymerization of ethylene?

$$\mathrm{ROOR} \xrightarrow{\Delta \text{ or } h\nu} 2\,\mathrm{RO\cdot}$$

Question 1

Which of the following best explains why fluorine and iodine are not commonly used for the radical halogenation of alkanes?

Accepted Answer

Fluorine radical reacts violently, and iodine radical is too unreactive to remove a hydrogen atom.

Question 2

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

Accepted Answer

Tertiary radicals are more stable than secondary radicals.

Question 3

In the radical bromination of butane, why is 2-bromobutane the major product?

Accepted Answer

The secondary radical intermediate is more stable than the primary radical.

Question 4

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

Accepted Answer

A chlorine radical abstracts a hydrogen atom from methane, forming HCl and a methyl radical, which then reacts with Cl$$_2 to $$regenerate the chlorine radical.

Question 5

Which of the following is a correct initiation step for the radical polymerization of ethylene?

Accepted Answer

$$\mathrm{ROOR} \xrightarrow{\Delta 	ext{ or } h
u} 2\,\mathrm{RO\cdot}$$

Question 6

Which of the following best explains why peroxide has an effect on the addition of HBr to alkenes but not on the addition of HCl or HI?

Accepted Answer

The propagation steps for HBr addition are both exothermic, while those for HCl and HI are not.

Question 7

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

Accepted Answer

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

Question 8

Which of the following best describes the role of vitamin E in biological systems?

Accepted Answer

Vitamin E traps radicals formed in nonpolar systems such as cell membranes.

Question 9

Which of the following statements about the stereochemistry of radical halogenation at a chiral center is correct?

Accepted Answer

The radical intermediate allows for equal access from both sides, leading to a racemic mixture.

Question 10

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

Accepted Answer

Homolytic cleavage splits electrons equally, forming radicals; heterolytic cleavage gives both electrons to one atom, forming ions.

Question 11

Which of the following best explains why allylic and benzylic hydrogens are especially reactive in radical halogenation?

Accepted Answer

The resulting radicals are stabilized by resonance.

Question 12

Which of the following is the correct order of radical stability?

Accepted Answer

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

Question 13

Which of the following is a termination step in radical polymerization?

Accepted Answer

$$2\,\mathrm{ROCH_2CH_2\cdot} \rightarrow \mathrm{ROCH_2CH_2CH_2CH_2OR}$$

Question 14

Which of the following best describes the selectivity of bromine in radical halogenation?

Accepted Answer

Bromine is highly selective and prefers to abstract hydrogens from the most substituted carbon.

Question 15

Which of the following is a correct example of a chain-growth polymerization product and its use?

Accepted Answer

Poly(vinyl chloride) (PVC) – used for plumbing pipes and clear food packaging.

Question 16

Which of the following best describes the effect of peroxide in the addition of HBr to 1-butene?

Accepted Answer

Peroxide causes anti-Markovnikov addition, resulting in 1-bromobutane.

Question 17

Which of the following is a correct propagation step for the radical addition of HBr to an alkene in the presence of peroxide?

Accepted Answer

$$\mathrm{Br\cdot} + \mathrm{CH_2$=CH_2$} \rightarrow \mathrm{CH_2BrCH_2\cdot}$$

Question 18

Which of the following best describes the head-to-tail linkage in chain-growth polymerization?

Accepted Answer

The head of one monomer links to the tail of another, leading to a regular polymer structure.

Question 19

Which of the following best explains why chain-growth polymers are widely used in packaging and containers?

Accepted Answer

They are chemically inert, lightweight, and can be easily molded into various shapes.

Free Radical Chemistry and Radical Polymerization

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