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Saturday, 27 December 2014

Nmr problem...Our cock can interpret one




OUR COCK CAN INTERPRET ONE.......................................






Compound below has a composition a 68.2% C, 13.6% H and 18.2% O by mass.
  • A notable feature of the 1H spectrum is a multiplet of nine at d1.7. What is the cause of this multiplet?
A splitting pattern of nine peaks must be produced by eight adjacent protons (8+1)


1H Spectrum

1H Spectrum (expansion)

  • Sketch the possible isomers of compound U, eliminating any which do not account for this multiplet of nine.

  • Assign each of the peaks, giving reasons for the relative intensities and splitting patterns.
Peak  is due to protons in position d as it has a chemical shift of d3.6 (corresponds to a -OH containing functional group) and is a triplet (split by two adjacent hydrogens - Hc).
Peak  is due the proton in position b as it has a chemical shift of d1.7 (corresponds to a tertiary -CH- group) and is a nontet (split by eight adjacent hydrogens - Ha and Hc).
Peak  is due to protons in position c as it has a chemical shift of d1.4 (corresponds to a -CH2 group) and is a quartet (split by three adjacent hydrogens - Hb and Hd).
Peak  is due to protons in position e as it has a chemical shift of d1.3 (corresponds to hydroxyl proton) and is a singlet (no splitting).
Peak  is due the proton in position a as it has a chemical shift of d0.8 (corresponds to a -CH3 group) and is a doublet (split by one adjacent hydrogens - Hb).


13C Spectrum


  • The 13C spectrum shows the reference peak and four peaks due to compound U. Explain.
Peak  is due to the carbon atom in position d as it has a chemical shift of d60.7 (corresponds to a -C-O- functional group) and is connected to an even number of protons (2).
Peak  is due to the carbon atom in position c as it has a chemical shift of d41.5 (corresponds to a secondary carbon group) and is connected to an even number of protons (2).
Peak  is due to the carbon atom in position b as it has a chemical shift of d24.6 (corresponds to a tertiary carbon group) and is connected to an odd number of protons (1).
Peak  is due to the two carbon atoms in position a as it has a chemical shift of d22.5 (corresponds to a primary carbon group). It can be seen that the carbon atoms are also connected to an odd number of protons (3).






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