Question

Predict the ratios (%) in which these monochlorination products will be formed, remembering that a chlorine atom abstracts a secondary hydrogen about 4.5 times as fast as it abstracts a primary hydrogen.

In the chlorination of pentane gives a mixture of three monochlorinated products.

Answer 1

There are 6 primary hydrogens to get 1-chloropentane, 4 secondary hydrogens to get 2-chloropentane and

2 secondary hydrogens to get 3-chloropentane.

Therefore, Ratio of no. of hydrogens available to get 1-chloropentane vs 2-chloropentane vs 3-chloropentane

= 6 : 4 : 2

Given that a chlorine atom abstracts a secondary hydrogen about 4.5 times as fast as it abstracts a primary hydrogen.

Therefore, corresponding reactivity factor = 1 : 4.5 : 4.5

Final ratio = 1x 6 : 4.5x 4 : 4.5x 2

= 6:18:9

= 2:6:3

Therefore, Ratio three monochlorinated products = 1-chloropentane : 2-chloropentane : 3-chloropenatne = 2:6:3