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NOESY spectrum of codeine

 

NOESY spectrum of codeine

  The sample is 3.3 mg of codeine in .65 ml CDCl3

A contour plot of the NOESY spectrum is shown below.  As with all homonuclear 2D plots, the diagonal consists of intense peaks that match the normal spectrum, as do projections onto each axis.   The interesting information is contained in the “cross-peaks”, which appear at the coordinates of 2 protons which have an NOE correlation.

For small molecules, the NOE is negative.  Exchange peaks have the opposite sign from NOE peaks, making them easy to identify.  The water peak at 1.5 ppm exchanges with the OH at 2.9 ppm, shown here in red.

The spectrum is phased with the large diagonal peaks inverted (shown in red here), so the NOE cross-peaks are positive.

 

Expansion of the upfield region:

 

Table of NOEs: ( indicates the more upfield of geminal CH2 protons)

8 – 7, 12
7 – 18, 18′
3 – 5, 10
5 – 11, 16, 18′
9 – 10, 17, 17′
10 – 16
11 – 18, 16, 14, 18′
18 – 13, 18′
16 – 14, 17
13 – 14, 17, 17′
13′ – 17, 17′
17 – 17′

In addition to confirming assignments, the NOESY spectrum allows stereospecific assignments of methylene Hs.  The 3 cross-peaks indicated in red on the plot below distinguish between the 3 CH2 pairs:

5 -18′
16 – 17
18 – 13
These NOEs can be viewed interactively in 3D using Chime.

Acquisition parameters:

512 complex points in the direct dimension
256 t1 increments
mixing time: 0.8 sec
experiment is hypercomplex (method of States, et al) and phase sensitive
16 scans
2 sec relaxation delay
Total time: 5 hrs.

Processing parameters:

cosine squared window function (sine function with 90 degree phase shift) in both dimensions
phased so all peaks in first slice are inverted
2x zero-fill in the indirect dimension
final size 512 x 512

See also: processing details, phase problems in noesy spectra, baseline problems in noesy spectra


Last updated: 01/22/2003