Since the order of ease of substitution in halogenation is

Tertiary hydrogen > Secondary hydrogen > Primary hydrogen

Then why in case of chlorination of iso butane CH₃--CH(CH₃)--CH₂--Cl is major product (67%) and (CH₃)--C--Cl is minor product (33 %).

Please explain!!!

 What you have said yes for typical nucleophilic substitution reaction and this reaction is chlorination and mechanism is free radical mechanism this you need to check for probability factor also here for the major product you have 9 hydrogen to be replaced but for the minor product you had only one hydrogen to be replaced this by probability factor you get it is easy to replace one among nine and not the other one if you want more details about this probability factor please tell me how to upload any media here

 

HAR