Q 28P - Organic Chemistry (Mcmurry)

Question

What product(s) would you expect from the reaction of 1-methyl cyclohexene with NBS? Would you use this reaction as part of a synthesis?

Step-by-Step Solution

Answer

                                                                  A mixture of six products

Step-by-Step Solution Step 1: 1-methyl cyclohexene

1-methyl cyclohexene reacts with NBS in the presence of light and carbon tetrachloride is used for the abstraction of hydrogen to generate allylic radical. On which attack of bromide ion takes place to form the corresponding product.

In 1-methyl cyclohexene, there are three different types of allylic H present that are marked as follows:

                Different allylic hydrogens

Step 2: Mixture of products

Abstraction of each allylic hydrogen generates two allylic radicals, each one capable of adding a bromine atom. Hence, a mixture of 6 products is possible.

                                                                   Mixture of six products

Since a mixture of products is obtained, this reaction cannot be used as a part of synthesis. This is because, in synthesis, one major product is desired so that we get a good yield of the target molecule.