Most professors just want you to be able to determine the major product of a radical halogenation. However some are going to get a little more crazy!

Here I’ll teach you how to predict the exact percentages of monohalogenation products for differing halogens at room temperature. Again, only some professors will ask you for this. Be sure to refer to your class notes to see if this is something you should learn!

Concept #1: Explaining relative rates of halogenation.

Example #1: Draw all of the monochlorination products of butane. Calculate percentage yields of each product.

By multiplying the number of equivalent hydrogens by its relative rate of halogenation, we can obtain a “*relative reaction*” rate. We compare the relative reactions to determine the percentage breakdown for each product.

I’ve made it really easy for you by building and filling out this chart. Eventually you should be able to fill in this chart yourself ;)

The percentages we yield correspond to the amount of each product we would expect if we were to run this halogenation ourselves.

Practice: What is the percentage yield of the major product?

Practice: What is the percentage yield of the major product?

In both the following exercises, assume that all the methylene groups in the alkane are equally reactive as sites of free-radical chlorination.
(a) Photochemical chlorination of heptane gave a mixture of monochlorides containing 15% 1-chloroheptane. What other monochlorides are present? Estimate the percentage of each of these additional C7H15Cl isomers in the monochloride fraction.

In both the following exercises, assume that all the methylene groups in the alkane are equally reactive as sites of free-radical chlorination.
(a) Photochemical chlorination of heptane gave a mixture of monochlorides containing 15% 1-chloroheptane. What other monochlorides are present? Estimate the percentage of each of these additional C 7 H 15 Cl isomers in the monochloride fraction.

Photochemical chlorination of 2,2,4-trimethylpentane gives four isomeric monochlorides.
(b) The two primary chlorides make up 65% of the monochloride fraction. Assuming that all the primary hydrogens in 2,2,4-trimethylpentane are equally reactive, estimate the percentage of each of the two primary chlorides in the product mixture.

Draw all of the monobromination products of the molecule below. Calculate the percentage yields of each product. The relative rates for each position are given below.

Draw all of the monoclorination products of the molecule below. Calculate the percentage yields of each product.