Stacked plot

Figure 2.10. HH COSY diagram of quinoline (11) [(CD3)2CO, 95% v/v, 25°C, 400 MHz, 8 scans, 256 experiments]. (a) Stacked plot (b) contour plot...

Figure 2.13. Symmetrised two-dimensional INADEQUATE experiment with isopinocampheol (2) [ CDshCO, 250 mg in 0.3 ml, 25 °C, 50 MHz, 256 scans and exp.], (a) Stacked plot of the section between 8c = 20.9 and 48.2 (b) complete contour plot with cross signal pairs labelled a-k for the 11 CC bonds of the molecule to facilitate the assignments sketched in formula 2...

The pulse sequence which is used to record CH COSY Involves the H- C polarisation transfer which is the basis of the DEPT sequence and which Increases the sensitivity by a factor of up to four. Consequently, a CH COSY experiment does not require any more sample than a H broadband decoupled C NMR spectrum. The result is a two-dimensional CH correlation, in which the C shift is mapped on to the abscissa and the H shift is mapped on to the ordinate (or vice versa). The C and //shifts of the //and C nuclei which are bonded to one another are read as coordinates of the cross signal as shown in the CH COSY stacked plot (Fig. 2.14b) and the associated contour plots of the a-plnene (Fig. 2.14a and c). To evaluate them, one need only read off the coordinates of the correlation signals. In Fig. 2.14c, for example, the protons with shifts Sh= 1.16 (proton A) and 2.34 (proton B of an AB system) are bonded to the C atom at c = 31.5. Formula 1 shows all of the C//connectivities (C//bonds) of a-pinene which can be read from Fig. 2.14. 

Figure 2.27. Sequence of measurements to determine the C spin-lattice relaxation times of 2-octanol (42) [(CD3)2C0, 75% v/v, 25 °C, 20 MHz, inversion-recovery sequence, stacked plot]. The times at which the signals pass through zero, xo, have been used to calculate, by equation 10, the T values shown above for the nuclei of 2-octanol...

The whole sequence of successive pulses is repeated n times, with the computer executing the pulses and adjusting automatically the values of the variable delays between the 180° and 90° pulses as well as the fixed relaxation delays between successive pulses. The intensities of the resulting signals are then plotted as a function of the pulse width. A series of stacked plots are obtained (Fig. 1.40), and the point at which the signals of any particular proton pass from negative amplitude to positive is determined. This zero transition time To will vary for different protons in a molecule. 

Figure 1.40 Stacked plots of H-NMR spectra for ethylbenzene. This experiment can be used to measure the spin-lattice relaxation time, T].

Two-dimensional NMR spectra are normally presented as contour plots (Fig. 3.11a), in which the peaks appear as contours. Although the peaks can be readily visualized by such an overhead view, the relative intensities of the signals and the structures of the multiplets are less readily perceived. Such information can be easily obtained by plotting slices (cross-sections) across rows or columns at different points along the Fi or axes. Stacked plots (Fig. 3.11b) are pleasing esthetically, since they provide a pseudo-3D representation of the spectrum. But except for providing information about noise and artifacts, they offer no advantage over contour plots. Finally, the projection spectra mentioned in the previous section may also be recorded. 

Heteronuclear two-dimensional /-resolved spectra contain the chemical shift information of one nuclear species (e.g., C) along one axis, and its coupling information with another type of nucleus (say, H) along the other axis. 2D /-resolved spectra are therefore often referred to as /,8-spectra. The heteronuclear 2D /-resolved spectrum of stricticine, a new alkaloid isolated by one of the authors from Rhazya stricta, is shown in Fig. 5.1. On the extreme left is the broadband H-decoupled C-NMR spectrum, in the center is the 2D /-resolved spectrum recorded as a stacked plot, and on the right is the con tour plot, the most common way to present such spectra. The multiplicity of each carbon can be seen clearly in the contour plot. 

Stacked plot The 2D NMR spectrum is presented as a series of ID spectra parallel to the F axis stacked together at a number of values (or vice versa), one below the other. 

A typical stack plot is shown below (Figure 8.3) and, whilst the intriguing appearance may conjure images of prog rock album covers, stack plots are not in the least user-friendly in terms of interpretation ... 

FIGURE 31 -10 Cerebral amino acids and carbohydrates incorporate 13C label from infused glucose. The top panel shows a 13C NMR spectrum obtained from a gray-matter-rich volume in the human head. (From reference [141].) The right panel shows label incorporation into brain glycogen and glucose in humans. (From reference [142].) The stack plot illustrates the rate of label incorporation into many compounds and carbons in the rat brain. (From reference [ 143].) In all studies, glucose labeled at the 1 or 6 position was administered intravenously. 

Fig. 5 Time-resolved in-situ EDXRD data showing the intercalation of LiCl into gibbsite at 120 °C. a 3D stacked plot, b Plot of extent of reaction of the (001) reflection of gibbsite (o) and the (002) reflection of [LiAl2(OH)6]Cl- H2O (A) as a function of time. Reproduced with permission from Chem Mater (1999) 11 1771-1775...

Fig. 13 3D stacked plots of the in-situ EDRXD data for the intercalation of methylphospho-nate into a Rhombohedral LiAl - Cl. b Hexagonal LiAl - NO3. c Rhombohedral LiAl - NO3... 

Fig. 14 Time-resolved data for the intercalation of methylphosphonate into hexagonal LiAl - Br. a 3D stacked plot, b Extent of reaction vs. time plots for host, intermediate and product...

Fig. 22 In-situ EDXRD data for the intercalation of naproxen into hexagonal LiAl - Cl. a 3D stacked plot for the reaction at 31 °C. b Plot of extent of reaction vs time for the (004) reflection of the intercalate over a range of temperatures...

Fig. 23 3D stacked plot illustrating the intercalation of ibuprofen into hexagonal LiAl - Cl as monitored using EDXRD. The presence of an intermediate phase is clearly visible... 

Fig. 37. Stacked plot of spectra recorded from the lower leg of a 35-year-old male volunteer. Spectra were recorded each 15 s during exhaustive exercise inside the imager (spectra 1 to 5) and in the recovery phase after exercise (spectra 6 to 16). Four acquisitions were recorded for each FID with TR = 3 s.

Fig. 3.19 Stacked plot of a C T, Inversion-Recovery experiment with peracetylated...

Try out the effect of the buttons in the button panel. The three display mode buttons Stack Plot, 3D, Overlay, which toggle between different display modes and the buttons Mouse Grid and Separate. Use Files to selectively delete the files 003999.1 R to 005999.1 R. Click first on the File Param. and then on the Next Trace button until the file 009999.1 R is selected. Change the Y-Scaling to 0.5 and inspect the multiple display again. 

Stacked mode Displays the data set in a stacked plot form. Local functional... 

Fig. 31. Stacked plot of the heteronuclear two-dimensional J-resolved spectrum of cured, carbon black filled, natural rubber. The proton flip experiment was used with high-power proton decoupling during the detection time. The experiment was performed with the sample spinning at the magic angle (reprinted from Ref. 1911 with permission)...

Fig. 2.50. Generation of /-resolved two-dimensional 13C NMR spectra (a) flux diagram (b) /-modulation of Cl l doublets, CH2 triplets and CH3 quartets during evolution, vector diagrams in the x y plane and cosine curves described by the signal maxima (c) series of 13C NMR spectra of CHn groups with t1 dependent /-modulation of the signal amplitudes (d) series of /-resolved two-dimensional 13C NMR spectra formethine, methylene and methyl carbon atoms, stacked plots and contour plots (e).

The two-dimensional matrix can be recorded by an analog plotter, or much faster by a digital plotter or a graphic display. Stacked plots as drawn in Fig. 2.50(d) can be obtained, providing a panoramic picture of the carbon-13 signals (3) and their individual multiplets (JCHj. Useful for practical evaluation, the contour plot is like a contour map of the signal mountains, giving a type of aerial view of the CH multiplets (Fig. 2.50(e)). 

Fig. 2.52.. /-Resolved two-dimensional 13C NMR spectra of biotin (100.6 MHz for 13C, 400.1 MHz for H 40 mg in 0.1 mol/ L aqueous sodium hydroxide measuring time 25 min transform time 12.5 min) stacked plot before (a) and after rotation (b) of the matrix by 90 " [62] (c) contour plot with one-dimensional 13C NMR spectra recorded with and without proton decoupling.

Fig. 2.54. Two-dimensional carbon-proton shift correlation of mutarotated D-lactose (1 mol/L in deuterium oxide , 3C 100.6 MHz H 400.1 MHz measuring time 90min transform lime 2.5 min) (a) stacked plot [64] (b) contour plot. 

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