二维核磁共振谱原理ppt课件.ppt

1、2D 核磁共振谱,1,2,3,4,5,6,7,COSY: Hypothetical Coupling,8,COSY: 1H-1H Coupling,9,10,Coupling networks can be traced out, as shown in the figure below.,COSY Spectrum of Codeine,11,Table of COSY correlations,COSY Spectrum of Codeine,12,13,14,15,What You See In a NOESY. . .,16,突出表现NOE效应的NOESY谱,17,18,NOESY.

2、. .,19,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

3、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

4、 here in red. The spectrum is phased with the large diagonal peaks inverted (shown in red here), so the NOE cross-peaks are positive.,20,Expansion of the upfield region:,8 - 7, 127 - 18, 183 - 5, 105 - 11, 16, 189 - 10, 17, 1710 - 1611 - 18, 16, 14, 1818 - 13, 1816 - 14, 1713 - 14, 17, 1713 - 17, 17

5、17 - 17,NOESY Spectrum of Codeine,21,Table 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 distinguish between the 3 CH2 pai

6、rs:,5 -1816 - 1718 - 13,NOESY Spectrum of Codeine,22,23,24,2 D C-H相关谱（C-H COSY),25,2 D 远程C-H COSY,26,Heteronuclear Multiple Quantum Coherence (HMQC) and Heteronuclear Multiple Bond Coherence (HMBC): 2-D inverse H,C correlation techniques that allow for the determination of carbon (or other heteroato

7、m) 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 HMBC,27,HMQC (trans-ethyl 2-butenoate),28,HMQC Heteronuc

8、lear Multiple-Quantum Coherence Experiment,29,C(9)-H,C(9)-H,HMQC Heteronuclear Multiple-Quantum Coherence Experiment,30,HMQC (1-Bond CH Correlation) of Codeine,31,This is a 2D experiment used to correlate, or connect, 1H and 13C peaks for atoms separated by multiple bonds (usually 2 or 3). The coord

9、inates 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 information obtained is an extension of that obtained from an HMQC spectrum, but is more complicated to analyze. Like HMQC, this is

10、 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 Z-gradients for improved spectral quality. The time required for an HMBC depends on the amount of material, but is much greater t

11、han for HMQC, and can take from an hour to overnight.,HMBC (Multiple-Bond CH Correlation) of Codeine,32,Peaks occur at coordinates in the 2 dimensions corresponding to the chemical shifts of a carbon and protons separated by (usually) 2 or 3 bonds. The experiment is optimized for couplings of 8 Hz.

12、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 suppress 1-bond correlations, but a few are observed in most spectra. In concentrated samples of conjugated systems, 4-bond cor

13、relations 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 peaks, testing for consistency and checking to be sure none of the assignments would require implausible or impossible coupling

14、s. 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 discussed below.,HMBC (Multiple-Bond CH Correlation) of Codeine,33,HMBC (Multiple-Bond CH Correlation) of Codeine,34,The discussio

15、n 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 generates a unique identifier for each Carbon, even before knowing any assignments.,HMBC (Multiple-Bond CH Correlatio

16、n) of Codeine,C9-H,C3-H,C5-H,1,2,3,4,5,6,35,C9-H,C3-H,C5-H,17,HMBC (Multiple-Bond CH Correlation) of Codeine,36,More 1D and 2D-Sepctra for Codeine,37,1D 1H and 13C NMR Spectra of Codeine,C18H21NO3, MW= 299.4 Data acquired on a JEOL Eclipse+ 400 spectrometer,1H spectrum:,C3-H,C5-H,C10-H,C7-H,C8-H,C9-

17、H,C12-H3,C11-H,C16-H,C18-H,C18-H,C17-H,C14-H,C3-H,C5-H,C9-H,C3-H,C5-H,38,13C spectra 18 mg sample, 1.3 hrs acquisition time,1,2,3,4,5,6,7,9,10,11,12,13,14,15,16,17,18,1D 1H and 13C NMR Spectra of Codeine,39,Peak Assignments for Codeine,40,Both experiments are used to identify multiplicity (quaternar

18、y, 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 transferred to 13C. This polarization transfer enhances sensitivity. Also, the experiment repetition rate is dependent on relaxation of 1H, rather than 13C, so a shorter delay is needed. DEPT also can distinguish between CH and CH3, unlike APT, alth