C8953
NMR structural analysis - seminar
Vector model & edited 13C NMR spectra
Jan Novotný
176003@mail.muni.cz
March 13, 2024
Determine percentage of dominant regioisomer in
attached 1
H spectrum:
Diastereotopicity1
Determine the equivalency of
geminal protons
1
http://www.chem.wisc.edu/areas/reich/chem605/
Values of chemical shift of important solvents
Abbr. Formula 1
H 13
C
ACN CH3CN 1.9 118
Benzene C6H6 7.2 128
CHCl3 7.2 77
DCM CH2Cl2 5.3 54
DMF (CH3)2NCHO 2.9, 8.0 32, 163
DMSO (CH3)2SO 2.5 40
MeOH CH3OH 3.3, 4.8 49
Water H2O 4.8 EXPLAIN
effect of solvent on the position of residual 1H water
signal:
CHCl3 - 1.6, ACN - 2.1, DMSO - 3.3, MeOH - 4.9
T1 relaxation
Apply following sequence (inversion recovery) to isolated spin characterized by
a) τ = 2 ∗ T1 and b) τ = 0.2 ∗ T1. Draw semi-quantitatively resulting spectrum.
τ
180x 90y-
Processing simulated NMR signal:
1-1 sequence
Draw the evolution of macroscopic magnetization through the sequence:
90(y) - τ - 90(y) - aq
Consider the evolution of an isolated spin due to the chemical shift.
1. How does the result differ for the following offsets: Ωτ = 0, π/2, π.
2. Draw lineshapes of resulting signal assuming the a) y+ b) x+ corresponds to zero
phase of receiver (prior phase correction).
τ
90y 90y
Heteronuclear spin echo
By using vector diagrams determine the result of attached pulse sequence.
1. Ignore 180 pulse in hydrogen channel for isolated spin systems a) 13C-1H and
b) 13C-1H2. Explain the role of CPD block.
2. Lets consider the complete sequence and isolated spin systems a) 13C-1H and
b) 13C-1H2.
τ=1/2J
90y 180x
13
C
τ=1/2J
180x
1
H
CPD
13
C APT Cinnamic acid
13
C APT Nicotine
DEPT experiment