= Solution
Write $t=\mathrm{C(CH_3)_3}$. \b[D is the <sodium> <enolate> $\mathrm{t{-}C(O^-){=}CH_2\ Na^+}$.] Its two resonances in the <alkene>-<proton> region belong to the two <hydrogens> of the terminal <methylene group>. One is cis to <oxygen> and the other trans to <oxygen>, so they are not related by a <symmetry (physics)> operation even though both belong to the same <carbon>. Replacing one or the other gives different alkene geometries, so they are <diastereotopic>. Their weak or unresolved <geminal coupling> is consistent with the reported singlet descriptions. Without an additional spatial assignment, it is not justified to decide uniquely which numerical shift belongs to which of those two orientations. The nine-<proton> singlet is the <tert-butyl group>. The formula $\mathrm{C_6H_{11}ONa}$ follows from removing one alpha <hydrogen> from <pinacolone>.
\b[E is the <enol>-dominated <1,3-diketone> $\mathrm{tCO{-}CH_2{-}COt}$, observed as $\mathrm{tC(OH){=}CH{-}COt}$.] The very downfield broad signal belongs to the <enol> OH in a six-membered intramolecular O–H···O chelate. The one-<proton> signal in the vinyl region is its central <enol> CH; a predominantly diketo structure would instead require a two-<proton> central CH2 signal and no <enol> OH. The eighteen-<proton> singlet accounts for both <tert-butyl groups>. Rapid exchange between the two degenerate <enol> orientations can average their different local environments; accidental unresolved equality cannot be excluded by the supplied spectrum alone. Thus one should not infer a permanently symmetric single <enol> <Lewis structure> from that singlet. The total integration is $1+1+18=20$, agreeing with \b[$\mathrm{C_{11}H_{20}O_2}$].
Back to article page
