Question #44942

Consider the following statements regarding the structural, thermodynamic, and acid-base properties of nitrogenous compounds at $298\text{ K}$:

\begin{enumerate} \item[(I)] $2,6$-Dimethyl-$N,N$-dimethylaniline is a stronger base than $3,5$-dimethyl-$N,N$-dimethylaniline because the bulky \textit{ortho}-methyl groups force the $-\text{NMe}_2$ group out of the ring plane, preventing the delocalization of the nitrogen lone pair. \item[(II)] In aqueous solution, the lactim (enol) tautomer of Uracil is thermodynamically favored over the lactam (keto) tautomer due to the attainment of complete Hückel aromaticity in the pyrimidine ring. \item[(III)] The $pK_b$ of $2$-methylaniline is higher than that of aniline due to the 'ortho-effect', which arises primarily from the steric hindrance to the hydration of the resulting anilinium cation. \item[(IV)] The thermal denaturation of DNA results in a hyperchromic shift at $260\text{ nm}$ due to the disruption of hydrogen bonds and base stacking, while the covalent phosphodiester backbone remains intact. \end{enumerate}

Which of the following combinations of statements is CORRECT?