# Orientation of halogenation

I was going through my chemistry book (RT Morrison and Boyd) and found a statement:

" the collision frequency of isopropyl and n-propyl w.r.t. Chlorine atoms is the same."

Is it correct because I think the size will matter in this case while both have the same weight?

• Welcome! A little bit more context would be nice, like which reaction is this talking about, and what environment. – Martin - マーチン Feb 17 '15 at 9:04
• While the collision frequency may be the same, the reaction rates will differ. This is because not all collisions cause a reaction. The isopropyl radical will be more stericly hindered than the n-propyl radical. – Mr T Apr 19 '15 at 21:15

It is clear that n-propyl radical and Isopropyl radical have same carbon structure. In the next step the hydrocarbon radical reacts with a chlorine ($\ce{Cl2}$) and since chlorine is symmetrical the collision frequency cannot depend upon it. It should be easy to judge from the following structures, the very minor difference: