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- 1. NMR SPECTROSCOPY 1 NMRSPECTROSCOPY Submitted to: Dr. T. Prabha M.Pharm., PhD., Professor,HOD Department of Pharmaceutical Analysis, Nandha college of Pharmacy, Erode-52. Submitted by: NANDHAKUMAR. A M.Pharm I Sem, Department of Pharmaceutics Nandha College of Pharmacy, Erode-52.
- 2. NMR SPECTROSCOPY 2 SOLVENTREQUIRMENTS IN NMR Characteristics of Solvents: Chemically inert solvent is used. Solvents should be magnetically isotropic in nature. Free from any hydrogen (1 H) atom. proton neutron Hydrogen 1 0 Deuterium 1 1 Hydrogen1/2 Deuterium1/2+1/2=1=I
- 3. NMR SPECTROSCOPY 3 Solventshould able to dissolve the molecule/sample in a reasonable quantity (Approximate 10% or more). Commonly used Solvents. 1)Carbon tetrachloride (CCl4) 2)Carbon disulphide (CS2) 3) Deuterochloroform (CDCl3) 4)Hexachloroacetone (CCl3)2CO) 5)Deutero dimethyl sulfoxide ( Deuterium containing DMSO) 6)Deuterobenzene (C6D6)
- 4. NMR SPECTROSCOPY 4 Factoraffecting the solvent: Hydrogen Bonding: *It will increase the δ value, & deshielding occurs. *Higher conc. of OH or NH group leads to hydrogen bonding & and electron cloud transfer from Hydrogen & ultimately deshielding takes place. *δ value of the same sample will be different.
- 5. NMR SPECTROSCOPY 5 Relaxationprocess: NMR relaxation is the processes by which an excited magnetic state return to its equilibrium distribution. The mechanism by which the higher energy state can lose energy to its environment and then return to its lower energy state is called the Nuclear relaxation process. Types of magnetic relaxation 1. spin-lattice or longitudinal relaxation (T1) 2. spin-spin or transverse relaxation (T2)
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- 8. NMR SPECTROSCOPY 8 1.Spin - Lattice Relaxation The nucleus in the higher energy state transfers it's energy to the other nuclei in the surrounding molecular framework i.e. lattice. Thus bringing that nucleus in low energy state. The time taken for this transition is known as Spin- Lattice Relaxation time. This will represent the lifetime of the nucleus in the higher energy state. For solid sample the relaxation time 10 -4 to 10-2 s. For liquid sample the relaxation time 10-4 to 10 s. Cause due to local magnetic fields (molecular tumbling) o If tumbling is too slow – magnetic field weak or strong or too fast o If tumbling- magnetic field (same frequency as for flip β-α)
- 9. NMR SPECTROSCOPY 9 Spin- Spin Relaxation when two processing nuclei come close to one another the nucleus in high energy state transfers it's excess of energy to the neighboring nuclei. This mutual exchange of spin give rise to spin- spin Relaxation. It does not alter the population distribution but its limits the time spent by the nuclei in higher energy level.
- 10. NMR SPECTROSCOPY 10 NMRSignals in various compounds Spin-spin splitting/coupling: Interaction with neighbouring hydrogens are called spin-spin splitting. (2nI+1)Rule/(n+1)Rule: n= Number of protons in neighbouring nuclei I=spin, hydrogen I value-1/2 2n+1=(2*n+1/2)+1 =(n+1)rule n=0 singlet n=1 doublet n=2 triplet
- 11. NMR SPECTROSCOPY 11 Pascal’sTriangle: 1 singlet n=0 1:1 doublet n=1 1:2:1 triplet n=2 1:3:3:1 quartet n=3 1:4:6:4:1 quintet /pentet n=4 1:5:10:10:5:1 sextet n=5 1:6:15:20:15:6:1 septet n=6 1:7:21:35:35:21:7:1 octet n=7
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- 16. NMR SPECTROSCOPY 16 Reference: 1.https://youtu.be/LHuIEBfMEqI?si=yGNMqD4_sM -I9opp . 2. Instrumental analysis Skoog . Holler . Crouch. 3. Keeler J. Understanding NMR spectroscopy. John Wiley & Sons; 2010 May 24.
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