¹H NMR spectrum A corresponds to a molecule with the formula C₃H₅Cl. The compound shows significant IR bands at 730 (see Problem 53 of Chapter 11), 930, 980, 1630, and 3090 cm^-1.

(a) Deduce the structure of the molecule.

(b) Assign each NMR signal to a hydrogen or group of hydrogens.

(c) The “doublet” at δ = 4.05 ppm has J ≈ 6 Hz. Is this in accord with your assignment in (b)?

(d) This “doublet,” upon five-fold expansion, becomes a doublet of triplets (inset, spectrum A), with J < 1 Hz for the triplet splittings. What is the origin of this triplet splitting? Is it reasonable in light of your assignment in (b)?

Problem 53

From the Hooke’s law equation, would you expect the C – X bonds of common haloalkanes (X = Cl, Br, I) to have IR bands at higher or lower wave-numbers than are typical for bonds between carbon and lighter elements (e.g., oxygen)?