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Solutions to Problems 199 Compounds are readily distinguished by their NMR spectra: The first one has no signals downfield of δ = 2. whereas the others do. The latter will also show different numbers of signals. The second compound has two nonequivalent methyl groups, whereas the third has two identical methyls. 3.7 1.7 1.6 3.6 Var (2) (2) (2) (2) (1) CICH₂ 3.7 (2)* 1.1 2.0 3.6 Var (3) (1) (2)* (1) 1.5 4.0 Var (6) (2) (1) Compounds are again distinguishable. The number and integration of signals downfield of δ = 3 distinguishes the last compound. The other two are distinguished by the presence of an upfield methyl signal in one but not in the other. CH₃ 1.5 (3) The last two compounds are readily identified. The second of these contains three equivalent methyl groups, giving a single signal of (c) intensity 9. Although the other three compounds all have four signals. only the third one has two signals downfield of δ = 3 (with 4.0 2.0 1.1 a total integration of 3). The first two compounds will be difficult to (2)* (1) (6)* distinguish by NMR-they each have the same number of signals with the same integration ratios. Only minor differences in chemical shifts will be present. CH₃ 1.2 (3) 3.7 2.0 1.5 (2)* (1) (6)* 3.7 1.3 4.0 1.5 (2)* (6)* (1) (3) 4.0 4.2 1.1 (2)* (1) (9)