Shifting of groups in carbocation rearrangement

![enter image description here](https://i.stack.imgur.com/NsMMA.jpg)


Phenyl has greater migratory power. However, why did methyl migrate in step 2 of the reaction?




In general, migratory aptitude of different groups follow following order: 
$\ce{-Ph} > \ce{-C(CH3)3} > \ce{-CH(CH3)2} > \ce{-CH2CH3} > \ce{-CH3} > \ce{-H}$


For example, 2,3-diphenylbutane-2,3-diol (**1**) was allowed to react under homogeneous (25 mol% of *p*-toluenesulfonic acid) or heterogenious (20 mol% of graphene oxide) catalytic conditions using toluene as a solvent at $\pu{100 ^\circ C}$. Under both conditions, only pinacol rearrangement with phenyl migration was observed affording 3,3-diphenylbutan-2-one (**2**) in a 90 and 95% conversion. Methyl migration has not been observed [Reference].


[![Pinacole](https://i.stack.imgur.com/ixC4N.jpg)](https://i.stack.imgur.com/ixC4N.jpg)


**Reference:**


Pinacol Rearrangement and Direct Nucleophilic Substitution of Allylic Alcohols Promoted by Graphene Oxide and Graphene Oxide $\ce{CO2H}$: M. Gomez-Martinez, A. Baeza, D. A. Alonso, *ChemCatChem*, **2017**, *9*, 1032–1039 (<https://doi.org/10.1002/cctc.201601362>)


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