Question

QUESTIONS HO — а Hab The 'H-NMR of the product shows two doublets in the aromatic region (at ~7.8 ppm and 6.7 ppm with equal relative integration) H. and a very broad signal (the signal is almost flat from ~5.0 ppm to ~6.5 ppm and may actually extend into the doublet at ~ 6.7 ppm) which may indicate a "combination" of the amine and acid peaks. W h o o Hd The amine group can be considered to be electron donating toward the ring by resonance, thus it will place a partial negative charge on the relative) ortho and para positions. Draw three resonance structures for the product, showing the resulting charges at these positions. Will this resonance effect lead to shielding or deshielding for the protons labelled as Hb compared to Hc? Based on your answer, which of the protons (Hb or Hc) should be at larger chemical shift (lower field)? Explain briefly. The carboxylic acid is considered to be electron withdrawing by resonance, thus it will place a partial positive charge on the relative) ortho and para positions. Draw_three_resonance structures for the product, showing the resulting charges at these positions. Will this resonance effect lead to shielding or deshielding for the protons labelled as Hc compared to Hb? Based on your answer, which of the protons (Hb or Hc) should be at larger chemical shift (lower field)? Explain briefly C. Assign each of these two proton sets to its corresponding signal on the spectrum. Page 4 of 5

Answer 1

22-Diney NH2 atatz GNH2 INH2 11 CoolH Cool OOH CODA соң NH₂ liti OH ó H og oH OH OH N-H stretch Te: 3300-3500 cm (sharp) 3300-500 cmt: 2 INHA (5.65) Ei - 6.7ppm (6) 2600-3100 cm to 0-4 stretch Broad cauid) CT7B(C) Cood (1212) 1600 cm': NH Bending • Boom to (-ostretch.

A) Amine group donates electron to the ring through + R effect. therefore, it increases electron density at ortho and para position. Otha Proton will be more shielded. therefore, ortho Proton will resonate at a higher field. consequently they will have a lower Delta value than Hc.

B) carboxylic acid withdraws electron density Through The - R effect. Hence, it decreases electron density at ortho and para position. therefore, ortho proton, Hc will be highly deshielded. consequently, it will resonate at lower magnetic field. thereby having a higher Delta value then Hb.