The relative susceptibilty of a hydrogen atom to chlorination is dependent on the degree of substitution at the carbon to which it was bound. For the radical chlorination of 1-chlorobutane, both the 1,2- and 1,3-dichlorobutane products involve 2nd degree-structures. However, 1,2-dichlorobutane was more than twice as present in the products as 1,3-dichlorobutane. Account for the differencees between the two.