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Exercise: Radical addition of hydrogen halides to alkenes

Exercise

Which of the following statements regarding the radical HI addition to alkenes are true?

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In contrast to chlorine and bromine, the bond energy of the C-I bond is not enough to compensate for the large amount of bond energy that is consumed by the cleavage of the C-C π bond.

The bond energy of the C-I bond is enough to compensate for the smaller amount of bond energy that is consumed by the cleavage of the C-C π bond.

The addition of an iodine radical to a double bond is an endothermic reaction.

In contrast to the radical iodination, the additions of chlorine and bromine radicals to double bonds are endothermic reactions. Therefore, they proceed rapidly enough to exceed the chain termination reactions.

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Exercise

The radical hydrogen chloride addition to alkenes virtually never occurs, although the addition of a chlorine radical to a double bond is an exothermic reaction. Why?

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Because in the second step of the chain propagation, the cleavage of the strong H-Cl bond consumes more energy than is released by the formation of the new C-H bond. As a result, this step is an endothermic reaction.

Because in the second step of the chain propagation, the cleavage of the strong H-Cl bond consumes more energy than is released by the formation of the new C-H bond. As a result, this step is an exothermic reaction.

Because in the second step of the chain propagation, the cleavage of the strong C-H bond consumes more energy than is released by the formation of the new H-Cl bond. As a result, this step is an endothermic reaction.

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Exercise

Which of the following statements are true?

Please make a choice.

Please make a choice.

correct

wrong

partly correct

This is the right answer

In the radical HBr and HI addition to alkenes, the second step of the chain propagation is an endothermic reaction.

In the radical HCl as well as HI addition to alkenes, one of the chain propagation steps does not exceed the chain termination reactions.

HBr is the only reagent that can be added to alkenes in a radical addition.

Anti-Markovnikov hydrogen halide addition products are preparatively useful because they cannot be produced by ionic additions.

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