Chapter 9, Problem 41P

When dissolved in $CDC{l}_3$, a compound (K) with the molecular formula $C_4{H}_8{O}_2$ gives a ${}^{1}HNMR$ spectrum that consists of a doublet at $\text{δ}$ 1.35, a singlet at $\text{δ}$ 2.15, a broad a singlet at $\text{δ}$ 3.75 (1H), and a quartet at $\text{δ}$ 4.25(1H). When dissolved in $D_{2}O$, the compound gives a similar ${}^{1}HNMR$ spectrum, with the exception that the signal at $\text{δ}$ 3.75 has disappeared. The IR spectrum of the compound shows a strong absorption peak near 1720 $c{m}^{-1}$.

(a) Propose a structure for compound K.

(b) Explain why the NMR signal at $\text{δ}$ 3.75 disappears when $D_{2}O$ is used as the solvent.