13Carbon Nuclear Magnetic Resonance.pptx

This presentation includes information on theory, principle, chemical shifts, number of signals, example, applications of CARBON 13 NMR.

1. 13 C NMR SPECTROSCOPY GUIDED BY Prof.Dr. Dinesh Mehta M.Pharm, PhD PRESENTED BY Tanuj Sharma(1424713) Course: M.Pharmaceutics M.M. COLLEGE OF PHARMACY,MMDU, MULLANA

2. CONTENTS: INTRODUCTION PRINCIPLE &THEORY 13 C NMR NEED OF 13C NMR CHEMICAL SHIFTS NUMBER OF SIGNALS FACTORS AFFECTING 13C NMR DIFFERENCE – PNMR VS 13CNMR APPLICATIONS REFERENCES

3. INTRODUCTION NMR is a phenomenon exhibited by when atomic nuclei placed in a static magnetic field absorbs energy from radio frequency field of certain characteristic frequency. It results to give a spectrum with frequency on X-axis and intensity of absorption on y-axis. Two types of NMR Spectroscopy are used to characterize organic structure:- H-1 NMR:- TO determine the type and number of H atoms in a molecule. C-13 NMR: - Used to determine type of carbon atoms in the molecule.

4. PRINCIPLE & THEORY When energy in the form of radiofrequency is applied When applied frequency is equal to induced frequency Absorption of energy occurs Nucleus Starts resonating NMR signal is recorded

5. Nuclear magnetic resonance concern the magnetic properties of certain atomic nuclei. It concern the atom having spin quantum number. C-12 nucleus is not magnetic active because; C-12:- Proton 6, Neutron 6 Nuclear spin( I)= 0 C-13:- Proton 6, Neutron 7 Nuclear spin(I)=1/2 Relatively new technique as compared to H1 NMR

6. 13C NMR C-12 have no magnetic spin and produce no NMR signal. C-13 have magnetic spin(I)=1/2. C-13 account for only 1.1% of naturally occurring carbon. No coupling between C-13 and C C-13 have weak signal. C-13 have strong coupling with H C-13 have weak coupling with C

7. C-13 has only about 1.1% natural abundance(of carbon atoms). C-12 does not exhibit NMR behavior. As a result, C is about 400 times less sensitive than H nucleus to the NMR ph enomenon. Chemical shift range is normally 0 to 220 ppm. Normal C-13 spectra are “broadband, proton decoupled” so the peaks show as single lines. Number of peak indicates the number of type of carbon atoms.

8. Why 13C NMR Required ?? Proton NMR used for study of number of non-equivalent proton present in unknown compound. Carbon NMR is used to determine the number of non-equivalent carbons and to identify the types of carbon atoms(methyl, methylene, aromatic, carbonyl….) which may present in compound. 13C signals are spread over a much wider range than 1H signals making it easier to identify & count individual nuclei.

9. CHEMICAL SHIFT 1H range= 0 to ~12 ppm 13C range= 0 to ~220 ppm

10. NUMBER OF SIGNALS The no. of signals in a 13C spectrum gives the number of different types of carbon atoms in a molecule. Because 13C NMR signals are not split, the number of signals equals the number of lines in the 13C spectrum. In contrast to the 1H NMR situation, peak inte nsity is not proportional to the number of absorbing carbons, so 13C NMR signals are not integrated.

11. SPIN-SPIN SPLITTING OF C-13 NMR Homonuclear spin spin splitting:- Because of its low nature abundance there is a low probability of finding two C-13 atom next to each other in a single molecule. C-13-C-13 Coupling negligible Heteronuclear spin spin splitting:- C-13 will magnetically couple with attached proton and adjacent proton, N+1 rule is obeyed.

12. Splitting take place according to nI+1 rule Where n= no. of nuclei I= spin quantum number CH3= 3+1= 4 quartet CH2= 2+1= 3 triplet CH= 1+1= 2 doublet C= 0+1= 1 singlet

13. Interpreting 13C NMR- Ex- 2- Bromo butane

14. FACTOR AFFECTING C-13 NMR Electro negativity of nearby atoms:- C bonded to O,N or halogen absorb downfield because O,N and halogen pull electron away from nearby C-13 atoms which decrease their electron density and “DE shielding” them . Chain length:- Cl-CH2-CH2-CH2-CH2-CH3 Deshielding effect of Cl decreases as number of bonds between Cl and C increases.

15. Hybridization:- -sp3 C signal is in the range 0-90 -sp 2 C signal is in range 110-220 -C=O signal is at the low-field end in the range 160-220

16. DIFFERENCE BETWEEN PNMR & 13C NMR PNMR 13C NMR It is study of spin charges 1. It is study of spin changes of c of proton nuclei. carbon nuclei. 2 . Chemical shift range is 2. Chemical shift range is 0-240 0-14 ppm. Ppm. 3. Continuous wave method 3. Fourier transform technique is used. is used. 4. Slow process. 4. Very fast process. 5. Peak overlapping seen in 5. No peak overlapping seen in complex samples. Spectrum. 6. Solvent peak not observed. 6. S olvent peak is observed. 7. TMS peak is singlet. 7. TMS peak is quartet.

17. APPLICATIONS: C-13 NMR has elucidated and biochemical structure. C-13 NMR provides information about the backbone to molecule rather than periphery. C-13 nuclei are stable isotopes and hence it not danger to radiotracer. And also used for quantification of drug purity to determina tion of the composition of high molecular weight synthetic polymer.

18. REFERENCES:- A Text book of organic spectroscopy by Y.R.Sharma. Instrumental spectroscopy of Chemical analysis by G.R. Chatwal. www.Wikipedia.com