Q9(a). Structure from UV, IR, NMR and mass data: C₇H₈BrN
An organic compound having C, H, N and X gave the following spectral data: UV: λmax 240 (ε 8000), 300 (ε 100) nm; IR (KBr): νmax 3400, 3300, 3200 (w), 2900, 1620, 1600, 1500, 1380, 880, 820 cm⁻¹; ¹H NMR: δ 7.20 (1H, d, J = 9 Hz), 6.50 (1H, d, J = 3.5 Hz), 6.30 (1H, dd, J = 9 Hz and 3.5 Hz), 3.50 (2H, broad s, removed on adding D₂O), 2.30 (3H, s); Mass: m/z (RA) 187 (90), 185 (90), 186 (20), 184 (20), 160 (10), 158 (10), 106 (100). Find the structure of the compound and justify your answer.
Answer in brief
4-Bromo-3-methylaniline (4-bromo-3-methylbenzenamine), C₇H₈BrN; X = Br.
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Coversstructure elucidationbromine isotope patternnitrogen rule1,2,4-trisubstituted benzene4-bromo-3-methylanilineD2O exchange
All parts of Question 9
- 9(a) Structure from UV, IR, NMR and mass data: C₇H₈BrN10 marks
- 9(b) Dieckmann condensation, then hydrolysis and decarboxylation5 marks
- 9(c) Beer’s law for camphor; λmax of the methyl halides5 marks
- 9(d)(i) Birch reduction with ring closure: a spiro acid5 marks
- 9(d)(ii) Robinson annulation to a spiro enone5 marks