Organic Chemistry : Help with Radical Reactions

Study concepts, example questions & explanations for Organic Chemistry

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Example Questions

Example Question #63 : Reactions Types

Which reagent must be used with hydrobromic acid to convert 1-hexene to 1-bromohexane?

Possible Answers:

None of these

A peroxide

Correct answer:

A peroxide

Explanation:

The double bond in 1-hexene is across carbons one and two. Just adding HBr would put the bromine on carbon 2 because the bromine is more stable on the more highly subtituted carbon. If you want to put the bromine on the less substituted carbon (generating 1-bromohexane), you must carry out the reaction in the presence of peroxides. The mechanism involves a free radical on the secondary carbon and a bromine addition on the primary carbon.

Example Question #1 : Help With Radical Reactions

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Which site would the reagent N-Bromosuccinimide (NBS) be most likely to attack?

Possible Answers:

Correct answer:

Explanation:

The most substituted atom is most likely to be attacked, as a radical intermediate would be created. The radical intermediate would be most stable on the most substituted carbon.

Example Question #1 : Help With Radical Reactions

Which of the following reagents would create the product for the reaction below?

Screen shot 2015 10 24 at 10.14.31 am

Possible Answers:

 only

, AIBN (azobisisobutyronitrile) only

, hv and , AIBN (azobisisobutyronitrile)

, hv only

 and and , AIBN (azobisisobutyronitrile)

Correct answer:

, hv and , AIBN (azobisisobutyronitrile)

Explanation:

The radical reaction would create the anti-Markovnikov product shown and both , hv and , AIBN (azobisisobutyronitrile) effectively cause radical reactions. The bromine would then be substituted with the  group.

Example Question #3 : Help With Radical Reactions

Which of these steps in a free-radical halogenation of an alkene will not generate a radical molecule?

Possible Answers:

All of these steps

Initiation

Termination

Propagation

None of these steps

Correct answer:

Termination

Explanation:

Termination is the only step that does not generate a radical product. The termination step ends the reaction by bringing together two radical molecules to produce a stable non-radical product.

Example Question #67 : Reactions Types

Screen shot 2016 02 21 at 7.20.00 am

Classify the type of reaction given.

Possible Answers:

Rearrangement reaction

Heterolytic bond breaking

Homolytic bond breaking

Substitution reaction

Correct answer:

Homolytic bond breaking

Explanation:

Homolytic bond breaking occurs when a molecule breaks up to form two or more new products. In the reaction given, molecular chlorine forms two radicals in which one electron stays with each fragment formed.

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