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NMR Spectroscopy

  1. TOPIC : NMR SPECTROSCOPY SUBMITTED TO: DEPARTMENT OF CHEMISTRY SUBMITTED BY: VISHAL ARORA M Sc.(Semester-3)
  2. CONTENTS :- 1. INTRODUCTION OF SPECTROSCOPY :-- 2. NMR SPECTROSCOPY :-- 3. NMR SPECTRUM :-- 4. NUCLEAR SHIELDING & DESHIELDING :- - 5. CHEMICAL SHIFT :--
  3. 1. INTRODUCTION OF SPECTROSCOPY :-- “It is the interaction of electro-magnetic waves with matter and study of that electro-magnetic radiation is known as spectroscopy.” “When a charge particle is accelerated magnetic and electric field are produced which vibrates vertically towards the direction of transmission.”
  4. Spectrum :-- when a radiation is passed through prism or grating then its splitting in the different wave- length is called spectrum
  5. Types of spectrum :- -
  6. (1 )Continuous spectrum : When any light source passes through prism then it get dispersed in to continuous bands of different colours known as continuous spectrum. (2) Emission spectrum : Spectrum produce by emitted radiation is known as emission spectrum. (3) Absorption spectrum : Spectrum produce by absorption of electromagnetic radiation of specific wavelength.
  7. 2. NMR-Nuclear Magnetic Resonance Spectroscopy :- NMR involves the interaction between an oscillating magnetic field of E.M. radiation and the magnetic energy of the nuclei when these are placed in an external static magnetic field. The sample absorbs E.M. radiation in RADIO WAVE region. NMR technique consist in exposing the protons in an organic molecule to a power- full field. The protons will posses at different frequencies, now we irradiate these processing protons with steadily changing frequencies and observe the frequency at which absorption occur. Also NMR is a spectroscopy technique which is based on absorption of electromagnetic radiation in the radio frequency region (4 to 900Mhz ) by the nuclei of the atom. At some value of the field strength, the energy required to flip the protons matches the energy of the radiation, Absorption occurs and a signal is observed. Such a spectrum is called NMR SPECTRA.
  8. NMR SPECTRUM:-
  9. NUCLEAR SHIELDING & DESHIELDING:- NUCLEAR SHIELDING
  10. NUCLEAR DESHIELDING
  11. CHEMICAL SHIFT:- The ratio of difference in the position of a particular proton from the absorption position of a reference proton is known as the chemical shift of the particular proton, or the shifts(compared with a reference)in the position of NMR absorptions which arise due to the shielding & deshielding of protons by electrons are called chemical shift. Reference compound- Tetramethyl Silane(TMS)
  12. Why TMS is used as reference compound ? 1. It is chemically inert 2. Magnetically isotropic 3. Volatile 4. Nontoxic 5. Cheap. 6. Soluble in most of organic solvents. 7. It gives a single sharp absorption peak at higher field than almost all organic protons.
  13. COUPLING The interactions between the spins of neighbouring nuclei in a molecule may cause the splitting of NMR signal in the spectrum, this is known as Spin-Spin coupling. Ex: CH3-CH2-Br (a) (b) NMR signal of (a) proton show triplet due to protons (b). NMR signal of (b) protons show quartet due to protons (a). T
  14. APPTICATION OF NMR-SPECTROSCOPY:- 1. Identification of structural isomers. 2. Detection of hydrogen bonding. 3. Detection of aromaticity. 4. Detection of electronegative atom or group. 5. Conformational analysis. 6. Detection of double bond character. 7. Keto-enol tautomerism. 8. Elemental and Quantitative analysis.
  15. REFRENCE  INTRODUCTION TO SPECTROSCOPY……Donald L pavia gary M. Lampan george s, kriz james r. Vyvyan  ELEMENTARY ORGANIC spectroscopy by……Y.R sharma  Website…….www.Epgpathshala.Com
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