Migratory aptitude in Baeyer-Villiger reaction?

Question

In short, I do not understand how or why the migratory aptitude is as listed in every textbook I've read. Firstly, they talk about a positive charge being built up that is stabilised by the movement of the most substituted group. I cannot fathom such a build up in my mechanisms. Please help me understand this in a mechanistic fashion.

Answer 1

When unsymmetrical ketones are used, then order of migration of alkyl group is :

tert-alkyl, sec-alkyl > Benzyl,Pheny> Prim-Alkyl> cyclopropane >methyl

For Benzophenone p-OCH₃> CH₃> H> Cl> NO₂ in para- position