HW 3 Multinuclear NMR Name:
Points: C6800 Date:
Max. 100 points Spring 2015 Version A
1. (13 pts) The 119
Sn NMR resonance of the Sn atom at the apex of the square pyramid in 3
was found to be extraordinarily shielded, being observed at −2441.5 ppm. The value closely
approaches those of the stannocene derivatives, with their record high-field tin resonances
appearing in the range from −2100 to −2300 ppm. Explain these observations considering the
two resonance structures of pyramidane 3, covalent and ionic.
2. (38 pts) Draw all possible complexes [PFx(CN)6-x] and predict multiplicities of signals in
31
P and 19
F NMR spectra.
3. (10 pts) Mark protons of CH2 in the following molecule as homotopic (H), enantiotopic (E)
and diastereotopic (D). Find the symmetry point group of this molecule:
4. (15 pts) How could you establish by 1
H NMR spectroscopy that the following reaction took
place? Give at least three pieces of evidence.
5. (24 pts) Calculate relative populations of Te isotopomers of this cation. (Disregard the Se
isotopes, use  = 2, for the two-fold axis that interchanges the Te atoms)
Se
Te
Te
Se
Se
Se
Se
Se
2+