The NMR and IR spectra for four unknown compounds A through D are presented below and on the next two pages. Possible empirical formulas for them (not in any particular order) are C₆H₅Br, C₆H₆BrN, and C₆H₅Br₂N (one of these formulas is used twice—two of the unknowns are isomers). Propose a structure and suggest a synthesis of each unknown, starting from benzene. 

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1Η ΝMR 2 H 3 H 100 685 735 o IR 4000 3000 2000 1000 600 cm 7.5 7.4 7.3 7.2 Wavenumber 300-MHz 'H NMR IR-A spectrum ppm (8) Transmittance (%)