What happens when
(a)Propanone is treated with methylmagnesium iodide and then hydrolysed, and
(b)Benzene is treated with ${\mathrm{CH}}_3\mathrm{COCl}$ in presence of anhydrous ${\mathrm{AlCl}}_3 ?$

(a) When propanone is treated with methyl magnesium iodide and then hydrolyzed, tertiary butyl alcohol is formed. 
${\mathrm{CH}}_3-\mathrm{CO}-{\mathrm{CH}}_3+{\mathrm{CH}}_3\mathrm{MgI}\to {\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{OMgI}\stackrel{{\mathrm{H}}_3\mathrm{O}+}{⟶}{\left({\mathrm{CH}}_3\right)}_3\mathrm{COH}$
(b) When benzene is treated with CH₃COCl in presence of anhydrous AlCl₃, acetophenone is formed.
${\mathrm{C}}_6{\mathrm{H}}_6+{\mathrm{CH}}_3\mathrm{COCl}\stackrel{\text{ Anhyd. }{\mathrm{AlCl}}_3}{⟶}{\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COCH}}_3+\mathrm{HCl}$