NMR spcetroscopy
- 1. PRESENTED BY DIVYA V 1ST M PHARM PHARMACEUTICAL CHEMISTRY PRESENTED BY DIVYA V 1ST M PHARM PHARMACEUTICAL CHEMISTRY
- 2. 1D NMR 2D NMR COSY NOESY
- 3. It is a type of spectroscopy where the energy states of spin-active nucleus placed in a static magnetic field are interogated by inducing transitions between the states via radiofrequency irradiation. Contain sequence of radio frequency pulses. Plot-Chemical shift vs radiofrequency. Includes regular H-proton spectrum, C-13 spectra.
- 4. PRINCIPLE Consist of 2 sections #Preparation #Detection PREPARATION-A 90 ͦ pulse is applied which rotates the equilibrium magnetization along Z axis to Y axis
- 5. This induces a signal in receiver coil. The signal decays due to T2 relaxation & is called as FREE INDUCTION DECAY(FID) FOURIER TRANSFORMATION to get final 1D spectrum.
- 6. TYPES REGULAR Sample reaches equilibrium. RF signal is transmitted. Signal is evolved(FID) Fourier transformation Final spectra is obtained
- 7. DECOUPLED Heteronuclear coupling from another nucleus with magnetic spin causes the signal to split & sensitivity to fall. Apply decoupling is necessary. GATED DECOUPLING Apply decoupling during relaxation time.
- 8. OTHER METHODS OF DECOUPLING, -Off resonance -Solvent suppression -Deuterium substitution Nuclear overhauser effect The local field of one nucleus is affected by another nucleus. Causes reduction in intensity of signal.
- 9. 1D NMR SPECTRAL ANALYSIS Contain following information for analysis, #Chemical shift #Spin-Spin coupling #Intensity INTERPRETATION OF H-NMR No:of signals-Indicates how many different kinds of protons are present. Position of signals: Chemical shift. Intensity of signals: No:of protons. Splitting of signals: No:of nearby nuclei usually protons.
- 10. ANALYSIS OF C-13 NMR E.g. Propyl acetate
- 11. 2D NMR
- 12. DEFINITION It gives data plotted in space defined by 2 frequency axes rather than one.
- 13. PRINCIPLE A 90 ͦ pulse is provided to sample & then depending upon the type again a 90 ͦ pulse is provided & this time, signal FID is measured.
- 14. STAGES OF 2D NMR
- 15. TYPES # HOMONUCLEAR THROUGH-BOND CORRELATION METHODS *COSY *ECOSY *TOCSY *INADEQUATE # HOMONUCLEAR THROUGH BOND- CORRELATION METHODS *HSQC *HMBC *HETCOR # THROUGH SPACE CORRELATION METHODS *NOESY *ROESY
- 16. HOMONUCLEAR 2 Frequency is provided to same nuclei in sample. COSY Used to identify spins which are coupled to each other. 2 axes are proton chemical shift. Consist of 2 types of peaks * Diagonal peaks * Cross peaks Diagonal peak-Corresponds to normal 1D spectrum. Cross peak-Spin-Spin coupling.
- 17. Cross peaks appears in matched positions in the diagonal peaks. TYPES A)NORMAL COSY PULSE SEQUENCE
- 18. B)COSY 45 ͦ PULSE SEQUENCE C)LONG RANGE COSY PULSE SEQUENCE
- 19. D)MQF COSY PULSE SEQUENCE E.G. GERANIOL 2 13 4 5 6 7 CH3 8 CH3 9 CH3 10 OH
- 20. E.G. ASPIRIN 1 2 6 3 5 4 7 O OH O 8 9 O CH3
- 21. Fig;Cosy spectrum of aspirin
- 22. THROUGH SPACE CORRELATION METHODS NUCLEAR OVER-HAUSER EFFECT SPECTROSCOPY(NOESY) Developed to observe NOE in 2D spectroscopy. Useful in structural elucidation. Fig : Pulse in NOESY
- 24. Fig NOESY spectrum 12,14ditbutylbenzochrysene.
- 25. REFERENCES Spectrophotometric identification of organic compounds by Silverstein, Barsler and Morril. Fifth edition;227-267. Instrumental methods of chemical analysis by Gurdeep.R.Chatwal and Sham.k.Anand. Himalaya publishing house:4.73-5.63 1D and 2D NMR experiment methods by Dr.Shaoxiong.Wu : April 14:2011