Question

The correct match for the protons labeled in compound \(\mathrm{X}\) in Column M with the corresponding chemical shifts (\(\delta\), ppm) in Column N is

Column M		Column N
P	\(H_a\)	I	7.00 (ddd, \(J\) = 8.4, 7.3, 1.4 Hz, 1H)
Q	\(H_b\)	II	7.17 (dd, \(J\) = 8.4, 1.4 Hz, 1H)
R	\(H_c\)	III	7.59 (ddd, \(J\) = 8.4, 7.3, 1.4 Hz, 1H)
S	\(H_d\)	IV	8.12 (dd, \(J\) = 8.4, 1.4 Hz, 1H)

• A. \(P\rightarrow II;\ Q\rightarrow III;\ R\rightarrow I;\ S\rightarrow IV\)
• B. \(P\rightarrow I;\ Q\rightarrow IV;\ R\rightarrow II;\ S\rightarrow III\)
• C. \(P\rightarrow II;\ Q\rightarrow IV;\ R\rightarrow I;\ S\rightarrow III\)
• D. \(P\rightarrow I;\ Q\rightarrow III;\ R\rightarrow II;\ S\rightarrow IV\)

Hint:

A proton flanked by ring CH on both sides gives ddd (three J's); one flanked on only one side gives dd (two J's). Substituent effects then fix which is more upfield or downfield: OH shields ortho/para, NO2 deshields ortho/para.

Answer 1

The Correct Option is A

A second way to reach the same match is to estimate each proton's shift with rough substituent increments, instead of only ranking pairs qualitatively.

Take benzene's base shift as about $7.26$ ppm and add typical increments for $-\mathrm{OH}$ and $-\mathrm{NO_2}$: $-\mathrm{OH}$ shifts a proton by roughly $-0.5$ (ortho), $-0.1$ (meta), $-0.4$ (para); $-\mathrm{NO_2}$ shifts a proton by roughly $+0.95$ (ortho), $+0.26$ (meta), $+0.38$ (para).

Numbering the ring $\mathrm{C1}=\mathrm{OH}$, $\mathrm{C2}=\mathrm{NO_2}$, $\mathrm{C3}=H_d$, $\mathrm{C4}=H_c$, $\mathrm{C5}=H_b$, $\mathrm{C6}=H_a$:

• $H_d$ (C3): ortho to $\mathrm{NO_2}$, meta to $\mathrm{OH}$: $7.26+0.95-0.1\approx8.1$ ppm.
• $H_c$ (C4): meta to $\mathrm{NO_2}$, para to $\mathrm{OH}$: $7.26+0.26-0.4\approx7.1$ ppm.
• $H_b$ (C5): para to $\mathrm{NO_2}$, meta to $\mathrm{OH}$: $7.26+0.38-0.1\approx7.5$ ppm.
• $H_a$ (C6): meta to $\mathrm{NO_2}$, ortho to $\mathrm{OH}$: $7.26+0.26-0.5\approx7.0$ to $7.2$ ppm.

These rough numbers line up with the four experimental values: $H_d$ (about 8.1) matches $\mathbf{IV}$ (8.12), $H_b$ (about 7.5) matches $\mathbf{III}$ (7.59), $H_c$ (about 7.1) matches $\mathbf{I}$ (7.00), and $H_a$ (about 7.0 to 7.2) matches $\mathbf{II}$ (7.17).

The splitting patterns confirm this independently: $H_a$ and $H_d$ sit next to a substituted carbon on one side, so they only pick up one ortho and one meta coupling (dd), while $H_b$ and $H_c$ sit between two $\mathrm{CH}$ carbons and pick up a third coupling (ddd), matching $\mathbf{I}$/$\mathbf{III}$ as the ddd pair and $\mathbf{II}$/$\mathbf{IV}$ as the dd pair.

Both the shift estimate and the splitting-pattern logic converge on $P\rightarrow II$, $Q\rightarrow III$, $R\rightarrow I$, $S\rightarrow IV$, option (A).