Answer Happy

200 180 160 140 120 100 80 60 40 20 OH OH OH COOCH3 H3C. COOH H₂CO. CHO J & J A B a) (10 marks) The ¹3C NMR spectrum depicted above is that of one of the three compounds A, B or C. Match the spectrum to the appropriate compound, explaining your choice by calculating chemical shifts as appropriate and clearly indicating signal assignments for your chosen compound. Briefly comment on the observed chemical shifts and signal intensities. Use the information in the table below to assist you.
Substituent (Z) -CH3 -CHO -COOCH3 -COH -OH -OCH3 13C NMR Incremental Shifts for Substituted Benzenes Zipso Zortho Zmeta Zpara 8.9 8.6 2.3 2.1 26.9 31.4 0.7 1.3 1.3 1.5 -12.7 -14.4 -0.1 0.6 0.0 0.0 1.4 1.0 -2.9 5.5 4.9 5.1 -7.3 -7.7
b) (9 marks) For each of the compounds A, B and C above, predict the appearance of the ¹H NMR spectrum in terms of observed signal multiplicities, approximate chemical shifts (for aromatic protons, expected chemical shift range will suffice) and the expected relative intensities of the integrals. c) (5 marks) If you were given the ¹H NMR spectra of the two compounds below, clearly explain how you might distinguish between them by discussing the expected number of signals, chemical shifts, multiplicities and the expected relative intensities of the integrals for each. HạCH,CO. A OH HạCH,CO. B OCH₂CH3 d) (1 mark) How many signals would you expect to see in the ¹³C NMR spectrum of each compound?