11) Compound 042 has the molecular formula \( \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2} \). Analyse both the \( { }^{1} \mathrm{H} \) and \( { }^{13} \mathrm{C} \) NMR and propose a structure for compound \( \mathbf{0 4 2} \). For \( { }^{1} \mathrm{H} \) NMR, tabulate the chemical shifts, coupling constants and integration values. For the \( { }^{13} \mathrm{C} \) NMR, tabulate the chemical shifts and multiplicity (C, \( \mathrm{CH}, \mathrm{CH}_{2} \), or \( \mathrm{CH}_{3} \) ).