What is the correct assignment of the number of signals in the ¹³C NMR spectra of the following disubstituted benzene derivatives? A)I = 3 signals; II = 3 signals; III = 2 signals B)I = 3 signals; II = 4 signals; III = 2 signals C)I = 6 signals; II = 6 signals; III = 6 signals D)I = 3 signals; II = 4 signals; III = 3 signals

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Based on the spectral notation, the disubstituted benzene derivatives have the following substituents: I: One substituent at position 1 and two substituents at position 3 II: Two substituents at position 1 and one substituent at position 4 III: Two substituents at position 1 and one substituent at position 2 For I, there will be three signals since the two substituents at position 3 are equivalent and will produce a single signal, while the substituent at position 1 will produce two signals due to its nonequivalence with the equivalent substituents at position 3. For II, there will be four signals since the two substituents at position 1 are non-equivalent and will each produce a separate signal, while the substituent at position 4 will produce a single signal. For III, there will be two signals since the two substituents at position 1 are equivalent and will produce a single signal, while the substituent at position 2 is far enough away to not impact the NMR spectrum significantly. Therefore, the correct assignment of the number of signals in the ¹³C NMR spectra of the disubstituted benzene derivatives is: I = 3 signals; II = 4 signals; III = 2 signals. Hence, the best choice is B.

What Is the Correct Assignment of the Number of Signals