Chapter 13, Problem 13.54P

Reaction of 2-methylpropanoic acid $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}{\text{CHCO}}_{\text{2}}\text{H}\right]$ with ${\text{SOCl}}_{\text{2}}$ followed by 2-methylpropan-1-ol forms $X$. $X$ has a molecular ion at $144$ and IR absorptions at ${\text{2965, 2940, 1739 cm}}^{-1}$. Propose a structure for $X$.