Multiplet analysis

Hoye, T. R. Zhao, H. Method for Easily Determining Coupling Constant Values An Addendum to A Practical Guide to First-Order Multiplet Analysis in H NMR Spectroscopy . J. Org. Chem. 2002, 67, 4014-4016. 

Alternatively, ID analogues of 2D HSQC, HSQC-TOCSY, and HETLOC experiments and a selective version of/ -resolved spectroscopy using selective excitation and/or chemical shift filtering of proton or carbon resonances may be used for the measurement of coupling constants 49,51-59 Band-selective decoupling of some of the protons during acquisition leads to reduced multiplicity, and so facilitates the multiplet analysis.56... 

In a homonuclear decoupling experiment a particular multiplet is irradiated suppressing the coupling interaction between the irradiated nucleus and its coupling partners. A comparison of the standard coupled ID spectrum and the selectively homonuclear decoupled spectrum reveals which nuclei are coupled. Whether a homonuclear decoupling experiment or a 2D homonuclear COSY experiment would be the best solution for multiplet analysis in a one-dimensional spectrum depends very much on the nature of the problem under investigation. If a large number of multiplets need to be irradiated then a two-dimension approach may be preferable. 

There are two basic processing steps in the frequency domain, phase correction followed by baseline correction. These steps are necessary because in a real NMR experiment the spectrometer, the sample and the experimental parameters are not perfect in contrast to NMR-SIM which represents the ideal experiment. These imperfections can lead to distortions in the lineshape and a non-linear baseline that must be corrected to enable reliable spectral analysis and interpretation using integration and multiplet analysis. Although not a typical application for NMR-SIM these distortions can be simulated as illustrated in Check its 3.2.3.4 to 3.2.3.6. 

Multiplet analysis is one of the most useful analytical tools in ID WIN-NMR it simplifies the measurement of coupling constants, it is the first step in disentangling overlapping multiplets of complex multi-spin systems and it provides the input parameters for the WIN-DAISY computer analysis program. It is based on the AX approximation and uses distance measurement to build up coupling patterns by recognizing lines split by a common coupling constant. 

The multiplet analysis provides information on the micro structures in the seismic cloud. However, it does not give knowledge of absolute locations of individual multiplet clusters with the same order of precision to the relative location of events in a multiplet cluster. Moriya et al. (2002) proposed the multiplet-clustering method" to reduce the location error of multiplet clusters using the technique of clustering analysis. In this method, the waveforms of events in a multiplet group are stacked, and similar phases of the stacked waveforms are compared in time domain. Then, relative arrival time differences (i.e. relative locations between the stacked events) are more precisely determined. 

In the 93 experiment, about 60 % of located events belong to some of the multiplet groups. Figure 6 shows the result of precise relative mapping of a multiplet group (Moriya et al., 2002). The relative location error is estimated to be less than 1 m. The multiplet groups usually define planer structures with diameters of 2 - 12 m. Thus, the multiplet analysis sheds light on the micro structure of the total seismic cloud. 

Moriya, H., Nakazato, K., Niitsuma, H. and Baria, R. (2002). Detailed fracture system of the Soultz-sous-Forets HDR field evaluated using microseismic multiplet analysis.. Pure appl. Geophys., Vol. 159,517-541. 

A multiplet analysis of Fe K-Edge Is 3d pre-edge features of iron complexes. Journal of the American Chemical Society 119, no. 27 6297-6314. doi 10.1021/ ja964352a. 

Even experienced chemists, however, often struggle to extract all of the coupling constants from resonances that have four couplings in them (doublet of doublet of doublet of doublets, or dddd) and even more complex multiplets. A straightforward systematic method exists, however, that allows for complete analysis of any (even the most complex) first-order multiplet. Practicing this method on the more easily analyzed ddd multiplets discussed above will allow the student to gain confidence in its usefulness. This systematic multiplet analysis was most succinctly presented by Hoye and Zhao, and is presented below. 

Hoye TR, Hanson PR and Vyvyan JR (1994) A practical guide to first-order multiplet analysis in H NMR spectroscopy. Journal of Organic Chemistry 59 4096-4103. 

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