Q: Which method can generate free radicals from chlorine molecules?

Photolysis via light: $$\mathrm{Cl_2$} \xrightarrow{\text{light}} 2\mathrm{Cl^\cdot}$$

Q: Which of the following reactions is an example of radical substitution?

$$\mathrm{CH_4$} + \mathrm{Cl_2$} \xrightarrow{\text{light}} \mathrm{CH_3Cl} + \mathrm{HCl}$$

Question 1

Which of the following best describes a free radical in organic chemistry?

Accepted Answer

A species that contains one or more unpaired electrons

Question 2

Which method can generate free radicals from chlorine molecules?

Accepted Answer

Photolysis via light: $$\mathrm{Cl_2$} \xrightarrow{	ext{light}} 2\mathrm{Cl^\cdot}$$

Question 3

In the radical chlorination of methane, what is the role of light?

Accepted Answer

It initiates homolytic cleavage of $$\mathrm{Cl_2$} to $$form $$\mathrm{Cl^\cdot}$$ radicals

Question 4

Which of the following is a correct example of homolytic cleavage?

Accepted Answer

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

Question 5

During the propagation step of methane chlorination, which reaction occurs?

Accepted Answer

$$\mathrm{Cl^\cdot} + \mathrm{CH_4$} \rightarrow \mathrm{HCl} + \mathrm{CH_3$^\cdot}$$

Question 6

Which of the following is NOT a method for generating free radicals?

Accepted Answer

Hydration of alkenes

Question 7

What is the major product when $$\mathrm{HBr} is $$added to propene in the presence of peroxides?

Accepted Answer

1-bromopropane (Anti-Markovnikov product)

Question 8

Which step in a radical reaction involves the combination of two radicals to form a stable product?

Accepted Answer

Termination

Question 9

Which of the following alkyl radicals is the most stable?

Accepted Answer

Tertiary radical ($$\mathrm{(CH_3$)_3C^\cdot})$$

Question 10

Which statement best explains why radical addition of $$\mathrm{HBr} to $$alkenes in the presence of peroxides gives anti-Markovnikov products?

Accepted Answer

The bromine radical adds to the less substituted carbon, forming the more stable secondary radical

Question 11

Which of the following is a correct propagation step in the radical addition of $$\mathrm{HBr} to $$propene?

Accepted Answer

$$\mathrm{CH_3CH=CH_2$} + \mathrm{Br^\cdot} \rightarrow \mathrm{CH_3CH^\cdot}CH_2Br$$

Question 12

Which of the following reactions is an example of radical substitution?

Accepted Answer

$$\mathrm{CH_4$} + \mathrm{Cl_2$} \xrightarrow{	ext{light}} \mathrm{CH_3Cl} + \mathrm{HCl}$$

Question 13

Which of the following is a possible termination step in the radical chlorination of methane?

Accepted Answer

$$\mathrm{Cl^\cdot} + \mathrm{Cl^\cdot} \rightarrow \mathrm{Cl_2$}$$

Question 14

Which of the following best describes the difference between symmetrical and unsymmetrical bond breaking?

Accepted Answer

Symmetrical bond breaking (homolytic) gives two radicals; unsymmetrical (heterolytic) gives ions

Question 15

In the Fenton reaction, which species is generated as a free radical?

Accepted Answer

$$\mathrm{HO^\cdot} ($$hydroxyl radical)

Question 16

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

Accepted Answer

Tertiary radicals are more stable than secondary radicals

Question 17

Which of the following is a correct initiation step in the radical addition of $$\mathrm{HBr} to an $$alkene?

Accepted Answer

$$\mathrm{ROOR} \xrightarrow{	ext{heat}} 2\mathrm{RO^\cdot}$$

Question 18

Which of the following is a correct multi-step propagation sequence in the radical addition of $$\mathrm{HBr} to $$propene?

Accepted Answer

$$\mathrm{CH_3CH=CH_2$} + \mathrm{Br^\cdot} \rightarrow \mathrm{CH_3CH^\cdot}CH_2Br$$; $$\mathrm{CH_3CH^\cdot}CH_2Br + \mathrm{HBr} \rightarrow \mathrm{CH_3CH_2CH_2Br} + \mathrm{Br^\cdot}$$

Free Radicals and Radical Reaction Mechanisms in Organic Chemistry

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