Principle and working of Nmr spectroscopy

principle of NMR spectroscopy and working of NMR is givven in that slides

1. Principle and working of nmr spectroscopy Presented by, Prof. Pramod V.Burakale Dept. of P’ceutical chemistry IBSS,College of pharmacy Malkapur . 1

2. contents Introduction Basics of atomic structure Spin quantum No. What is NMR? Precessional frequency & motion Theory of NMR Larmor equation Instrumentation Types of NMR Advantages of FT-NMR 2

3. introduction NMR is the most powerful tool available for organic structure determination. NMR Spectrometry is based on the measurement of absorption of electromagnetic radiation in the radio frequency region of roughly 4 to 900MHz. In contrast to UV, IR and visible absorption, nuclei of atoms rather than outer electrons are involved in the process It is used to study a wide variety of nuclei: 1 H 13 C 15 N 3

4. Basics of atomic structure What is atom? Composition of atom? What is molecule? What is atomic No.? What is atomic mass No.? Different charges on atom? What is spinning nuclei? What is spin quantum No.? 4

5. 5

6. a Elements are composed of extremely small particles called atoms. All atoms of a given element are identical. The atoms of one element are different from the atoms of all other elements. A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds. 6

7. a Atomic No.- Number of Protons present in the nuclei of atom. Atomic mass No.- Number of protons and neutrons present in the nuclei of atom. Atomic mass no.= No.of protons+ No. of neutrons 7

8. Spin quantum number Spin quantum no denoted by ‘ I ’ Atom having I > o shows NMR spectra Spin quantum depends on atomic no.& atomic mass no. No. of possible orientation calculated using (2 I +1) 8 Mass NO. Atomic NO. Spin quantum No. odd odd or even ½, 3/2, 5/2……… even even even odd 1,2,3………………

9. what is nmr ? Nuclear Magnetic Resonance Matching of frequencies 9 In the Nucleus Involves Magnets

10. preCEssional frequency and motion Proton is act as tiny magnet in external magnetic field A slower waltz like motion of nuclei around axis known as precessional motion The precessional frequency may be defined as the number of revolutions per seconds made by the magnetic moment vector of the nucleus around the external field H Eg . Spinning top 10

11. preCEssional frequence and motion 11

12. theory of nmr Every charged nuclei having property of spinning. Induced magnetic field. Resonance. Absorption of energy. Flipping phenomenon. Measurement of release energy. Relaxation process. 12

13. theory of nmr (flipping phenomenon) 13

14. ENeRgy transition Nuclei with 2 allowed spin states can align either with or against the field, 14

15. T1 Relaxation 15 T1 relaxation is sometimes called spin-lattice relaxation . In this type of relaxation the energy lost as the nucleus returns to the lower energy state is transferred to the molecule in the form of heat.This means that the total number of nuclei in the excited state decreases.

16. T2 Relaxation T 2 relaxation is commonly refered as spin-spin relaxation. In this type of relaxation the energy released when a nucleus makes the transition from high to low energy state is absorbed by another nucleus. This allows the other nucleus to move from low energy to high 16

17. T2 Relaxation Short relaxation times result in broad signals. Longer relaxation times then produce narrower signals. An excited nucleus transfer it’s energy to an unexcited nucleus of a similar molecule that is nearby. 17

18. larmor equation v = ( g / 2 π ) Bo g = Magnetogyric ratio Bo = Magnetic field Larmor frequency: The nuclei precess about an axis parallel to the applied magnetic field, with a frequency called the Larmor Frequency (w) 18

19. Relation between ‘v’ and ‘ b o Slow precession in small magnetic field Faster precession in larger magnetic field 19

20. instrumentation 20

21. Role of different component Strong magnet Radio frequency source(input oscillator) A detector(output receiver) An amplifier Recorder Sample holder Coil around sample 21

22. Working of nmr spectrophotometer Sample under investigation taken in glass tube Rf source is made to fall on sample by feeding energy into the coil wound around the sample holder A signal is detected if nuclei in sample resonate with source Energy is transfer from via nuclei to detector source Output from detector is fed to recorder after amplification 22

23. Types of nmr CW NMR spectroscopy Magnetic field is steady and tunable radio frequency is use. It is operated on frequency sweep method FT-NMR spectroscopy Conversion of time domain spectra into frequency domain spectra. 23

24. New trends in nmr 24 FT-NMR

25. Advantages of ft- nmr over cwnmr More sensitive. It can measure weaker signal also, Required less time for scanning . Measurement of FID can performed in few second. Suitable for examination of nuclei that are not strongly magnetic. Also suitable for very dilute sample. Coupling constant is easily determine. 25

26. summary In NMR spectroscopy the electromagnetic radiation absorb in frequency region of 4-900 MHz Nuclei of atom involved in process Atom having I>0 shows NMR spectra Unless and until nuclei of atom not resonate with radio frequency it can not give spectra More will be the strength of external magnetic field more will be the frequency of rotation 26

27. References Skoog D.A, Holler F.J.& Crouch S.R.,”Instrumental Analysis” Page No. 552-567,577 William Kemp, “Organic Spectroscopy” 3 rd edition,Published by Palgrave, Page No. 103-118. 27

28. 28

29. 29