二維核磁共振譜原理

1、2D 核磁共振譜核磁共振譜COSY: Hypothetical CouplingCOSY: 1H-1H CouplingCoupling networks can be traced out, as shown in the figure below. The colored arrows trace out coupling networks, corresponding to: H-3 H-5 H-10 OHH-10 - H-9H-3 H-16H-16 H-11COSY Spectrum of CodeineTable of COSY correlationsshiftshiftAssig

2、nments 6.66.77 - 8 5.75.33 - 5 5.72.73 - 16 5.74.93-9 weak5.34.25 - 10 5.32.75 - 16 4.94.29 - 10 4.22.910 - OH 3.32.711- 16 3.32.411 - 14 3.32.311 - 18 3.02.418 - 14 3.02.318 - 18 2.62.413 - 13 2.62.113 - 17 2.61.913 - 17 2.42.113 - 17 2.41.913 - 17 2.11.917 - 17 COSY Spectrum of CodeineWhat You See

3、 In a NOESY. . .突出表現突出表現NOE效應的效應的NOESY譜譜NOESY. . .NOESY Spectrum of Codeine The sample is 3.3 mg of codeine in .65 ml CDCl3A 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 o

4、nto 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 p

5、pm 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: 8 - 7, 127 - 18, 183 - 5, 105 - 11, 16, 189 - 10, 17, 1710 - 1611 - 18, 16, 14, 1818 - 13, 1

6、816 - 14, 1713 - 14, 17, 1713 - 17, 1717 - 17 NOESY Spectrum of CodeineTable of NOEs: ( indicates the more upfield of geminal CH2 protons)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

7、distinguish between the 3 CH2 pairs:5 -1816 - 1718 - 13NOESY Spectrum of Codeine2 D C-H相關譜（相關譜（C-H COSY)2 D 遠程遠程C-H COSYHeteronuclear Multiple Quantum Coherence (HMQC) and Heteronuclear Multiple Bond Coherence (HMBC): 2-D inverse H,C correlation techniques that allow for the determination of carbon

8、(or other heteroatom) to hydrogen connectivity. Gradient HMBC (gHMBC) improves the acquired spectra by significantly reducing unwanted signal artifacts.HMQC is selective for direct C-H coupling HMBC will give longer range couplings (2-4 bond coupling). HMQC and HMBCHMQC (trans-ethyl 2-butenoate)HMQC

9、 Heteronuclear Multiple-Quantum Coherence ExperimentC(9)-HC(9)-HHMQC Heteronuclear Multiple-Quantum Coherence ExperimentHMQC (1-Bond CH Correlation) of Codeine1H13CAssignment6.611386.512075.713335.312854.89194.266103.856123.359113.0 & 2.320182.640162.6 & 2.446132.443142.0 & 1.83617This i

10、s a 2D experiment used to correlate, or connect, 1H and 13C peaks for atoms separated by multiple bonds (usually 2 or 3). The coordinates of each peak seen in the contour plot are the 1H and 13C chemical shifts. This is extremely useful for making assignments and mapping out covalent structure.The i

11、nformation obtained is an extension of that obtained from an HMQC spectrum, but is more complicated to analyze. Like HMQC, this is an inverse detection experiment, and is possible only on newer model spectrometers. Acorn NMRs new JEOL Eclipse+ 400 is equipped to perform inverse experiments, and uses

12、 Z-gradients for improved spectral quality.The time required for an HMBC depends on the amount of material, but is much greater than for HMQC, and can take from an hour to overnight.HMBC (Multiple-Bond CH Correlation) of Codeine Peaks occur at coordinates in the 2 dimensions corresponding to the che

13、mical shifts of a carbon and protons separated by (usually) 2 or 3 bonds. The experiment is optimized for couplings of 8 Hz. Smaller couplings are observed, but their intensities are reduced. Compare to the spectrum obtained when the experiment is optimized for 4 Hz.The experiment is designed to sup

14、press 1-bond correlations, but a few are observed in most spectra. In concentrated samples of conjugated systems, 4-bond correlations can be observed. There is no way to know how many bonds separate an H and C when a peak is observed, so analysis is a process of attempting to assign all observed pea

15、ks, testing for consistency and checking to be sure none of the assignments would require implausible or impossible couplings.Because of the large number of peaks observed, analysis requires several expanded plots. In this case, the spectrum has been divided into 4 sections, each of which is discuss

16、ed below.HMBC (Multiple-Bond CH Correlation) of CodeineHMBC (Multiple-Bond CH Correlation) of CodeineThe discussion below uses the numbering system shown at right. The numbers were assigned to peaks in the 1D 13C spectrum, starting downfield, moving upfield, and numbering each sequentially. This gen

17、erates a unique identifier for each Carbon, even before knowing any assignments.HMBC (Multiple-Bond CH Correlation) of CodeineC9-HC3-HC5-H123456C9-HC3-HC5-H17HMBC (Multiple-Bond CH Correlation) of CodeineMore 1D and 2D-Sepctra for Codeine1D 1H and 13C NMR Spectra of CodeineC18H21NO3, MW= 299.4Data a

18、cquired on a JEOL Eclipse+ 400 spectrometer1H spectrum:C3-HC5-HC10-HC7-HC8-HC9-HC12-H3C11-HC16-HC18-HC18-HC17-HC14-HC3-HC5-HC9-HC3-HC5-H13C spectra 18 mg sample, 1.3 hrs acquisition time123456791011121314,151617181D 1H and 13C NMR Spectra of CodeinePeak Assignments for Codeine13C (ppm)1H(ppm)1 146.3

19、q 2 142.23q 3 133.43CH5.71 4 131.13q 5 128.30CH5.29 6 127.30q 7 119.58CH6.57 8 113.03CH6.66 9 91.39CH4.8910 66.43CH4.1811 58.92CH3.3512 56.40CH33.8413 46.47CH22.59, 2.4014 43.12CH32.4415 42.99q 16 40.82CH2.6717 35.85CH22.06, 1.8818 20.46CH23.04, 2.30OH2.99Both experiments are used to identify multiplicity (quaternary, CH, CH2 or CH3) of peaks in a 13C spectrum. Usually, DEPT is preferred because much less time is required. For DEPT, 1H magnetization is generated first, then transfe