6. .
• For Curcumin, the proton (1H spectrum) shifts
are as follows. 2 similar protons on the
aromatic groups give rise to shifts at 5.55ppm
(aromatic C-OH). The benzene CH of which
there are 3, give rise to 7.16 ppm, 6.99 ppm
and 6.79 ppm. On the hexadienone bridge,
between the two benzene rings (aromatic
rings) are 2 pairs of equvalent protons
7. .
• 2 protons are found at 7.60 ppm, that are
attached to the aromatic Hydorgen and
Carbons. The 2 protons attached to the
carbonyl groups can be shown at 6.91 ppm.
Lastly, there are two protons in between 2
carbonyl groups at 4.69 ppm
13. 2D 1H-13C HSQC
Using information from 1H NMR data alone is not a
new concept. However, applications that also use
the 2D 1H-13C HSQC experiment are gaining
more interest as a result of the growing feasibility
of acquiring these spectra routinely. The 2D HSQC
experiment contains additional information (i.e.
13C chemical shift) as well as easier identification
of labile and diastereotopic protons.
20. 1H-Proton nmr carboxylated curcumin
• For carboxylated curcumin, the proton
spectrum differs from curcumin as follows.
• First, the carboxyllic chain gives rise to protons
at 11.0 (C-O-O-H) group, and 3 carbons at 2.02
ppm and 2 chemically equivalent at 2.30 ppm
• (CHa2 –CHb2-CHa2)
21. • As for the ring structure, it is primarily similar
to curcumin of course.
• It shows an C-O-H proton at 5.35 ppm , and 3
aromatic ring protons at 7.16 ppm, 6.99 ppm
and 6.79 ppm.
• The aromatic protons next to the carboxyllic
acid chain are now shifted to 7.30 ppm and
7.26 ppm
22. .
• The are also 2 peaks at 3.83 ppm due to C-OH
proton on both aromatic rings.
28. COSY
• COSY is one of the simplest and most useful
experiment. It is also one of the shortest 2D
experiment. It needs a minimum of 4
transients on conventional spectrometer (see
phase cycling - vector model or coherence
pathway). With the addition of gradients, only
one transient is needed which means that on
a modern spectrometer, the very precious
COSY information can be obtained in 5 min!!!
29. COSY
• This 2D experiment is composed of a 90
degree pulse that creates magnetization in the
transverse plane. During the evolution time,
the variable delay t1 is incremented
systematically in order to sample the spectral
width indirectly. Following this variable time
period, a second pulse mixes the spin states,
transferring magnetization between coupled
spins
30. COSY
• The spectra is then acquired during t2
(detection time). After double Fourier
Transformation, a spectra like the one below is
obtained showing a diagonal component (for
magnetization that did not exchange
magnetization) and cross peaks (off-diagonal)
for nuclei exchanging magnetization through
scalar coupling.
31. COSY
• The data is usually symmetrical respect to the
diagonal and therefore the data can be
symmetrized as part of the processing to improve
the quality (care must be taken here to make sure
that by getting rid of the non-symmetrical
artefacts we are not also getting rid of precious
information that might not be totally
symmetrical). The data is usually acquired in a
phase insensitive (magnitude mode) manner,
avoiding the difficulty to phase a 2D data set
