Nmr spectroscopy

that presentation try to help to understand easily a NMR spectroscopy

1. NMR SPECTROSCOPY Presented by salman

2. Out line Introduction Fundamental principles and theory Instrumentation Solvents Chemical shift Factor effecting chemical shift Interpretation of proton [ spectra NMR ] Application & types

3. introduction Nuclear Magnetic Resonance (NMR) is a spectroscopy technique which is based on the absorption of electromagnetic radiation in the radio frequency region 4 to 900 MHz by nuclei of the atoms Proton Nuclear magnetic resonance spectroscopy is one of the most powerful tools for elucidating the number of hydrogen or proton in the compound. It is used to study a wide variety of nuclei: 1H 15N 19F 19F 13C 31P

4. Fundamental principles All nuclei are electrically charged and many have spin. Transfer of energy is possible from base energy to higher energy levels when an external magnetic field is applied. The transfer of energy occurs at a wavelength that coincides with the radio frequency. Also, energy is emitted at the same frequency when the spin comes back to its base level. Therefore, by measuring the signal which matches this transfer the processing of the NMR spectrum for the concerned nucleus is yield.

5. Theory of Nuclear Magnetic Resonance (NMR) Some types of atomic nuclei act as though they spin on their axis similar to the Earth. Since they are positively charged they generate an electromagnetic field just as the Earth does. So, in effect, they will act as tiny bar magnetics. In the absence of an external magnetic field the direction of the spin of the nuclei will be randomly oriented Two possible orientations are possible, with the external field (i.e. parallel to and in the same direction as the external field) or against the field (i.e. antiparallel to the external field) If a proton that is precessing in an applied magnetic field is exposed to electromagnetic radiation of a frequency ν that matches its precessional frequency ωL , we have a condition called resonance.

6. instrumentation Sample holder – It is a glass tube which is 8.5 cm long and 0.3 cm in diameter. Magnetic coils – Magnetic coil generates magnetic field whenever current flows through it. Permanent magnet – It helps in providing a homogenous magnetic field at 60 – 100 MHZ. Sweep generator – Modifies the strength of the magnetic field which is already applied. Radiofrequency transmitter – It produces a powerful but short pulse of the radio waves. Radiofrequency – It helps in detecting receiver radio frequencies. RF detector – It helps in determining unabsorbed radio frequencies. Recorder – It records the NMR signals which are received by the RF detector. Readout system – A computer that records the data

7. Solvent used in NMR The following solvent are normally used in which hydrogen replaced by deuterium CCl4 carbon tetrachloride CS2 carbon disulfide CDCSl3 deuteriocholoform C6D6 Hexa deuteriobenzene D2O deuterium oxide

8. Chemical shift in NMR spectroscopy A spinning charge generates a magnetic field that results in a magnetic moment proportional to the spin. Chemical shift is characterized as the difference between the resonant frequency of the spinning protons and the signal of the reference molecule. There are also different nuclei that can be detected by NMR spectroscopy, 1H (proton), 13C (carbon 13), 15N (nitrogen 15), 19F (fluorine 19), among many more. 1H and 13C are the most widely used Both the nuts have a good charge and are constantly revolving like a cloud.

9. Factor effecting chemical shift The effective magnetic field becomes less than the applied magnetic field due to the shielding by electrons in the neighbourhood so the applied field requires an increase to bring about resonance. Electronegativity Anisotropy Hydrogen bonding

10. Interpretation of proton [ spectra NMR] As interpreting NMR spectra, the structure of an unknown compound, as well as known structures, NMR spectrum shows that x- axis is chemical shift in ppm. such as, chemical shift spin multiplicity coupling constants integration .

11. application In medicine Biochemistry Organic chemistry Flow measurement & angiography Tumour MRI

12. types There are two types of NMR spectrometers continuous-wave ( cw ) pulsed or Fourier-Transform (FT-NMR).