HW 3 Multinuclear NMR Name:
Points: C6800 Date:
Max. 100 points Spring 2011 Version A
1. Decide which isomer of the compounds below is present when the experimental value of
olefinic proton shift in the 1
H NMR spectrum is 8.22 ppm. (Calculate chemical shifts of
olefinic protons.)
2. How would you distinguish these two isomers. Give the symmetry point groups of the
molecules. Calculate chemical shifts of aromatic protons and carbons.
OH
OH
3. Consider two derivatives of the following anion:
A) R = F, B) R = CHMePh
a) Draw clearly all symmetry elements present in the anion.
b) Give the symmetry point group of this anion.
c) Are there any geminal groups? If yes, what class do they belong
to?
d) How many resonances (signals) do you expect in the 19
F NMR
spectra.
e) How would you explain, that in A there is only one signal at
room temperature.
4. How would you explain the number of signals in the 29
Si NMR spectra the following
molecules:
a) R = Ph, -145.9;
b) R = (R,S)-CHMePh, -146.1, -146.4, -146.6;
c) R = (R)-CHMePh, -146.2, -146.8;