Which of the carbon atoms in the following molecule appears furthest downfield in the ¹³C NMR spectrum?

Question

Quizplus · Accepted Answer

The carbon atom with the highest chemical shift (furthest downfield) will have the most deshielding around it. In this case, that would be the carbon attached to the two oxygen atoms (which are highly electronegative) and the nitrogen atom (which is also electronegative). This is carbon iii, as the other carbons are either attached to only one electronegative atom or are closer to the methyl group on the other end of the molecule.

Which of the Carbon Atoms in the Following Molecule Appears