Chemistry - GOC Question with Solution | TestHub

A and $\mathrm{C}$ are imides: their $\mathrm{N}-\mathrm{H}$ conjugate bases spread negative charge over nitrogen and two carbonyl oxygens. $\mathrm{B}$ is a lactam with only one carbonyl attached to nitrogen; $\mathrm{D}$ is an amine, not a lactam, and lacks this carbonyl stabilization. A, phthalimide, is more acidic than the saturated fused imide $\mathrm{C}$. Published $\mathrm{RHF}$/6-31G energies give deprotonation energies of about 1534.3 kJ ${\mathrm{mol}}^{-1}$ for A and 1539.9 for cis-$\mathrm{C}$ (1545.2 for trans-$\mathrm{C}$); the smaller value favors deprotonation of A. The source $\mathrm{C}$ key is therefore replaced by A.