Question 1

Which of the following best describes the process shown in the first image, where two half-headed arrows are used to break the A–B bond?

Accepted Answer

Homolytic cleavage, resulting in two radicals

Question 2

In radical halogenation of alkanes, which halogens are commonly used and why?

Accepted Answer

Chlorine and bromine, because their bonds are weak enough to homolyze under light or heat

Question 3

What is the hybridization and geometry of a carbon radical?

Accepted Answer

sp2-hybridized, trigonal planar

Question 4

Which step in the radical halogenation mechanism is the rate-determining step?

Accepted Answer

Propagation (abstraction of H atom to form carbon radical)

Question 5

Why are tertiary carbon radicals more stable than primary carbon radicals?

Accepted Answer

Tertiary radicals have more alkyl groups that donate electron density via hyperconjugation and inductive effects

Question 6

Which of the following best represents the energy profile for radical halogenation of ethane with chlorine?

Accepted Answer

Two transition states, with the first step being exothermic and the overall reaction exothermic

Question 7

What is the main reason that monohalogenation of alkanes often produces a mixture of products?

Accepted Answer

Halogen radicals react with every type of hydrogen in the molecule

Question 8

Which bond is most easily broken during radical halogenation, and why?

Accepted Answer

Tertiary C–H bond, because it is the weakest and forms the most stable radical

Question 9

In the reaction $$\mathrm{C_6H_{12} + Br_2$ \xrightarrow{h
u} C_6H_{11}Br + HBr}$$, what is the role of light ($$h
u$$)?

Accepted Answer

It initiates homolytic cleavage of the Br–Br bond to generate Br radicals

Question 10

Which of the following statements about radical initiators is correct?

Accepted Answer

Peroxides (RO–OR) are used because their O–O bond is weak and readily homolyzes to form radicals

Question 11

What is the product of radical halogenation of cyclopentane with chlorine under light?

Accepted Answer

Chlorocyclopentane and HCl

Question 12

Which step in radical halogenation is responsible for the formation of unwanted side-products?

Accepted Answer

Termination, where two radicals combine to form a stable bond

Question 13

What is the enthalpy change ($$\Delta H) $$for the overall radical halogenation of ethane with chlorine, based on the provided bond energies?

Accepted Answer

$$\Delta H_{overall} = -118\ \mathrm{kJ/mol}$$

Question 14

Which of the following statements about the mechanism of radical halogenation is correct?

Accepted Answer

The chain mechanism involves repeated propagation steps where radicals are regenerated

Question 15

Which type of carbon radical is least likely to undergo rearrangement?

Accepted Answer

Primary and secondary radicals

Question 16

What is the main driving force for radical reactions?

Accepted Answer

Radicals seek to achieve an octet by reacting with $$\sigma-$$bonds or other radicals

Question 17

Which arrow notation is used to represent the movement of a single electron in radical mechanisms?

Accepted Answer

Half-headed curved arrow (fishhook)

Question 18

In the radical halogenation of alkanes, what is the product when a secondary hydrogen is abstracted from ethane?

Accepted Answer

CH3CH2Cl

Question 19

Which of the following is true regarding the ease of hydrogen abstraction in radical halogenation?

Accepted Answer

Tertiary hydrogens are abstracted more easily than primary hydrogens

Radical Reactions in Organic Chemistry: Structure, Stability, and Halogenation Mechanisms

Study Guide - Practice Questions