(a) Two amides are constitutional isomers and have the formula C₄H₉NO, and each contains an isopropyl group as part of its structure. Give structures for these two isomeric amides.

(b) Draw the structure of two other amides with the formula C₄H₉NO that do not contain isopropyl groups.

(c) Draw the structure of a compound X that is a constitutional isomer of the amides in parts (a) and (b), but is not an amide, and contains both an amine and an alcohol functional group.

(d) Could a compound with the formula C₄H₉NO contain a nitrile functional group? Explain.