This is an example of pinacone pinacone rearrangemnt
acetone with Mg and H2O forms 2,3 Dimethylbutane2.3 diol
which on reacting with H+ from forms first a carbocation on carbon 2 then results is 1,2 methyl shift to form carbon 3 carbocation and then H+ is removed from O forming C=O final product is 3,3Dimethyl butan2 one