Compare rate of hydrohalogenation between 1,2-diphenylethene and 1-phenylpropene Consider the compounds, (I) - 1,2-diphenylethene and (II) - 1-phenylpropene. Compare their rate of hydrohalogenation (HX addition)



I feel that the answer should be (II) > (I), but to my surprise it's given to be (I) > (II).

My thoughts:


In (I), phenyl group consists of sp2 carbons, operates -I effect and destabilises the carbocation intermediate. 
In (II), protonation should occur at the carbon directly attached to the phenyl group. The methyl group (instead of phenyl, as in (I)) operates +I effect and stabilises the carbocation.
In both cases, the carbocation formed enjoys resonance stabilisation from a phenyl group - so it's not a factor we need to compare. 


So, what is the real order of rates of $\ce{HX}$ addition? Is my reasoning correct, or have I missed something?
I would suggest that there is a potential kinetic effect here.  While the most stable carbocation formed in either case is similar, the number of collisions that result in the formation of the more stable carbocation is higher in I than in II.

If we take a very simplified view of the possible collisions in II, we can see that in a reaction with $\ce{HCl}$ only "one" of the orientations of the collisions will result in the formation of the desired carbocation. 


In the case of I, "both" of the possible collisions will lead to the formation of the same stable carbocation.


If the number of possible effective collisions is higher, the reaction will be faster.