Question

SpectrosceP . Which structure is consistent with this 'H Which stracture is most consistent with this c NMR spectrum? NMR spectrum? CA) CH CH CHCH-OCH CHyCHCH CCH CH,CH CNHCH CHjCH-CHCHy MR and "C NMR spectra? CH-OCCH (B) CH Q OH 4. Which structure is in agreement with these 'H CHy · The chemical shifts in the CHy-O-C-NH-CH2-CH DC NMR spectrum for 1 3 this compound are δ 15.8, 40.1, 51.8 and 170.2. Which is the correct set of chemical shifts for the carbon atoms? carbon atom (A) 51.8 40.1 170.2 15.8 (B) 170.2 15.8 51.8 40.1 (C) 15.8 170.2 40.1 51.8 (D) 51.8 170.2 40.1 15.8 CH CH,CH CCH 0 OH CHyCH,CH CCH CHy

Answer 1

1) The nmr peak appears to be three sharp singlet which accounts for three sets of chemically equivalent protons. No spliting in the peaks are owing to the fact that the protons are insulated from each other. A sharp singlet near 7 indiactes that of a monosubstituted benzene ring. In this context of monosubstitution option D is ruled out, which contains disubtituted benzene. Moreover, in the context of singlet peaks due to non availbility of neighbouring protons causing splitting of peaks, option A is the correct answer , where protons are insulated from each other and hence no splitting occurs. Had it been the nmr spectra correspond to the compound B, C it would have splitted nmr peaks rather than sharp singlet.

Ans- option A