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Example Questions
Example Question #1 : Help With Radical Reactions
Which reagent must be used with hydrobromic acid to convert 1-hexene to 1-bromohexane?
None of these
A peroxide
A peroxide
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 #2 : Help With Radical Reactions
Which site would the reagent N-Bromosuccinimide (NBS) be most likely to attack?
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 #3 : Help With Radical Reactions
Which of the following reagents would create the product for the reaction below?
and and , AIBN (azobisisobutyronitrile)
only
, AIBN (azobisisobutyronitrile) only
, hv only
, hv and , AIBN (azobisisobutyronitrile)
, hv and , AIBN (azobisisobutyronitrile)
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 #2 : Help With Radical Reactions
Which of these steps in a free-radical halogenation of an alkene will not generate a radical molecule?
None of these steps
Termination
Initiation
All of these steps
Propagation
Termination
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 #2 : Help With Radical Reactions
Classify the type of reaction given.
Homolytic bond breaking
Substitution reaction
Rearrangement reaction
Heterolytic bond breaking
Homolytic bond breaking
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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