NMR Spectroscopy

Introduction,Instrumentation, chemical shift , Applications of NMR

1. Presented by Ujjwal Mandal M.pharm , 1 st sem , 1 st Year INTRODUCTION , INSTRUMENTATION & APPLICATIONS OF NMR

2. Contents Introduction Principle Shielding And Deshielding Chemical shift Instrumentation Applications of NMR Conclusion References 2

3. Introduction Of NMR Nuclear magnetic resonance spectroscopy or NMR is a powerful analytical technique used to characterize organic molecules by identifying carbon-hydrogen frameworks within molecules. Two common types of NMR spectroscopy are used….. : 1 H NMR is used to determine the type and number of H atom in a molecule. : 13 C NMR is used to determine the type and number of C atom in a molecule. The source of energy in NMR is radio waves , which have long wavelength. 3

4. Principle Nuclei with odd mass number( 1 H, 13 C, 19 F, 35 Cl etc.) only give NMR spectra. Spin quantum number (I) for such nuclei will be 1/2,3/2,5/2 etc. For example, 1 H I = ½ & Total possible orientation state (2I+1)=2 1.Ground state (-1/2) 2. Excited state(+1/2) Other nuclei with even mass number & even atomic number do not give NMR spectra. Like 12 C, 16 O 8 , Nuclei whose spin number, I=0 have no NMR spectra. 4

5. The theory behind NMR comes from the spin of nucleus and it generates a magnetic field. Without an external applied magnetic field, nuclear spins are random in direction. But when an external magnetic applied then the nuclei aligns themselves either with or against the field of the external Magnetic direction. 5 THEORY

6. Arrangement system 6

7. Shielding And Deshielding Effect When a proton is present inside such magnetic field, then more a pplied magnetic field is required for excitating . This protons are known as shielded protons. When a proton is present outside such circulating magnetic field,then less applied magnetic field is r equired for excitating.This protons are known as deshielded protons. 7

8. Chemical shift Chemical shift is the difference between the absorption position of the sample proton and the absorption of the reference standard (e.g. TMS). Variations of the positions of NMR spectra due to the electronic shielding or deshielding effect.This phenomenon known as spin-spin coupling (splitting). 8

9. Instrumentation RF transmitter- It is use for to apply a radiofrequency radiation. E.g. 60Mhz,100Mhz,220Mhz,300Mhz depending on the capacity of instrument. RF receiver/detector- It is use to measure the intensity of unabsorbed radio frequency energy. Sweep Generator – To vary the strength of the applied magnetic field. A field strength of 14,092 gauss,21,140 gauss etc are used. Sample cell – A sample test tube, which is about 25cm long and 5mm outer diameter is kept inside the sample cavity and is spun at 30rps. Recorder – It is used to record the NMR signal obtained from detector. 9

10. schematic DIAGRAM 10

11. Applications of nmr To characterize of molecular structure and nature. Determines purity and composition of a sample. Types and number of proton, carbon. Environment of proton, whether the proton is shielded or deshielded. Moisture analysis :- The % of hydrogen in the compound can be determined. 11

12. Conclusion Nuclear magnetic resonance spectroscopy is one of the most powerful tools that use to determine the structure of compounds. Generally, NMR spectroscopy gives the information about organic and inorganic compound. 12

13. References Dr. S. Ravi Sankar,Text book of Pharmaceutical Analysis,4 th edition,2010,Page-(6.1-6.9) Y.R. Sharma,Elementary Organic Spectroscopy,5 th edition,2015,Page-(191-241) Gurdeep R. Chatwal , Sham K. Anand , Instrumental Methods of Chemical Analysis,Himalaya Publishing House,2017,(Page-2.185-2.235) 13

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