logging in or signing up NMR BASICS salunkeamarjit Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: Embed: Flash iPad Dynamic Copy Does not support media & animations Automatically changes to Flash or non-Flash embed WordPress Embed Customize Embed URL: Copy Thumbnail: Copy The presentation is successfully added In Your Favorites. Views: 2079 Category: Science & Tech.. License: All Rights Reserved Like it (1) Dislike it (0) Added: February 21, 2011 This Presentation is Public Favorites: 2 Presentation Description NMR Fundamental concepts Comments Posting comment... By: kpu61 (25 month(s) ago) kindly permit me to download and read it leasurly to read,as this attracts me a lot Saving..... Post Reply Close By: salunkeamarjit (25 month(s) ago) give me ur mail id then i will send u dear Saving..... Edit Comment Close By: hetalkagarana (26 month(s) ago) hi,yr presentation is very helpful,can u send me copy of it on my email id email@example.com Saving..... Post Reply Close Saving..... Edit Comment Close By: salunkeamarjit (31 month(s) ago) thanks Saving..... Post Reply Close Saving..... Edit Comment Close By: chhabrajk (31 month(s) ago) Pls allow me to dld for personal use Saving..... Post Reply Close Saving..... Edit Comment Close By: chhabrajk (31 month(s) ago) Pls allow me to dld for personal use Saving..... Post Reply Close Saving..... Edit Comment Close loading.... See all Premium member Presentation Transcript PRESENTATION TREM USED IN DESCRIBING SPECTRA & THEIR INTERPRETATION : PRESENTATION TREM USED IN DESCRIBING SPECTRA & THEIR INTERPRETATION SUBMITED BY: SALUNKE AMARJIT M.PHARM-I DEPARTMENT: PHARMACEUTICSPRESENTATION TERM USING IN SPECTRA : PRESENTATION TERM USING IN SPECTRA INTRODUCTION TO NMR POSITIONS OF SIGNALS (CHEMICAL SHIFTS) SHIELDING & DESHIELDING PEAK AREA & PROTON COUNTING ANISOTROPIC EFFECT SPIN-SPIN SPLITTING COUPLING CONSTANT DOUBLE RESONANCE (SPIN DOCOUPLING) NUCLER OVER HAUSING EFFECTSlide 3: Fundamental Principles of NMR Magnetic property of nucleus:- We know that to move any body the energy will be required. Energy =Mass * Velocity But nucleus is revolving around its own axis so it is moving in circular direction Energy=Mass* angular momentum spin quantum number of the nucleus is related to atomic number & Mass numberSlide 4: Mass number Atomic number Spin quantum number Examples Odd Even or Odd 1/2,3/2,5/2 1 H, 13 C, 35 CI, 31 P Even Even 0 12 C, 16 O Even Odd 1 2 H , 14 NSlide 5: If spin quantum number (I) is ½ then spin states is calculated by formula Number of spin states = 2I + 1 =2* ½+1=2 So two orientation are possible so it act as magnetic If spin quantum number (I) is zero (0) than Number of spin states is 1, so it act as non magnetic 12 C, 16 O If spin quantum number (I) is 1 than Number of spin states is 3 The three orientations are in form of -I, 0, +I. 2 H , 14 NINTRODUCTION: INTRODUCTION NMR spectroscopy is concerned with magnetic properties of certain atomic nuclei, notably the nucleus of the hydrogen atom-the proton-and that of the carban-13 isotope of the carbon. This was historically discovered by PACKARD 1951. one example of proton NMR spectrum TolueneSlide 7: Chemical shift:- The difference in the absorption position of a particular nucleus from the adsorption position of a reference nucleus is called chemical shift of the particular nuclei. The chemical shift for a proton is determined by the electronic environment of the proton. Non-equivalent protons in a molecule have different chemical shifts The chemical shifts of vinylic, acetylenic and benzene protons are explained by ‘magnetic anisotropy”Slide 8: TMS is a good reference because It gives an intense sharp signal even at low concentration Silicon is electropositive. Silicon pushes electron into the methyl group of TMS by a positive inductive effect.& thus TMS comes to resonance at low frequency All of its hydrogen atom remain in identical environment & they are strongly shielded than the proton in any purely organic compoundSlide 9: It is chemically inert ,magnetically isotopic volatile27 o C &soluble in most organic solution. Does not make any intermolecular association with the sample For aqueous solution in which TMS is insoluble, the Sodium salt of 3-(trimethylsilyl)-propanesulfonic acid is usedSlide 10: Measurement of chemical shift:- δ Which is defined as proportional difference in parts per Million (ppm) from an appropriate reference standard The relationship between δ value (in ppm) & frequency in Hz is fundamentalSlide 11: Electro negativity-Shielding & Deshielding H 0 electron density partially shields the nucleus from H 0 so it “feels” H local electrons generate an induced field (H i ) which opposes H 0 H iSlide 12: In the presence of an applied magnetic field the valence electrons in the vicinity of the proton are forced to circulate and thus generate an induced magnetic field, which opposes the applied field. The valence electrons thus shield the proton from the applied magnetic field in an effect referred to as Local Diamagnetic Shielding . Electronegative elements added to the carbon atom to which the proton is attached produce a withdrawing effect that reduces the electron density about the proton. Reducing electron density deshields the proton from the effect of the applied field. Deshielding the proton produces a greater chemical shift. The chemical shift increases as the electronegativity of the attached element increases .Slide 15: Peak area and proton counting In NMR spectrum various peak represent equivalent proton sets. Toluene has two groups of hydrogen atoms the methyl hydrogen and the ring hydrogen. Two signals appear on spectrum, corresponding to these two different chemical and magnetic environments. In 1 st spectra the five ring proton and in 2 nd spectra three methyl proton. so the ratio of these area is 5:3Slide 16: compounds CH3X CH 3 H CH 3 I CH 3 Br CH 3 Cl CH 3 F Element X H I Br Cl F Electronegativity of X 2.1 2.5 2.8 3.1 4.0 Chemical Shift d 0.23 2.16 2.68 3.05 4.26Slide 17: ANISOTROPIC EFFECT The word "anisotropic" means "non-uniform". Magnetic anisotropy means that there is a "non-uniform magnetic field". Electrons in ∏ systems ( e.g. aromatics, alkenes, alkynes, carbonyls etc .) interact with the applied field which induces a magnetic field that causes the anisotropy.Slide 18: Spin – Spin Splitting In addition to the Chemical Shift and Signal Area, the NMR spectrum can provide information about the number of the protons attached to the carbon atom. Even in simple molecules, each type of proton rarely gives a single resonance signal. Protons are affected by the presence of protons on nearby, generally adjacent atoms. Multiple signals (multiples) are produced depending on the number of nearby protons in a phenomenon called Spin-Spin Coupling . Each type of proton “senses” the number of equivalent protons (n) on the carbon atoms next to the one it is bonded, and splits its resonance signal into n+1 signals.Slide 19: Spin-Spin Splitting 1,1,2-Trichloroethane (a) Cl C C Cl (a) (b) (b) H H H Cl Signal from a Signal from b Split into triplet by the two (b) protons Split into doublet by the (a) proton Proton H a Protons H b Possible spin combinations Signal Intensity Net Spin: +1 0 -1 1 2 1 +1/2 -1/2 1 1Slide 20: Pascal's TriangleSlide 22: Coupling constant (J) The distance the centers of the two adjacent peak in a multiplet is usually constant is called coupling constant. The value of “J” of generally lies between 0 and 20Hz.Slide 24: Nuclear over housing effect (N.O.E.) It has great value in studying the molecular geometry of the compound. It tells whether the two protons are in close proximity within the molecule or not. An important consequence of this effect is that the line intensities observed in the normal spectrum may not be the same as in the decoupled spectrum.Slide 25: References: Organic spectroscopy by WILLIAM KEMP. Elementary organic spectroscopy by Y.R.SHARMA. Introduction to spectroscopy by PAVIA. Goggle.co.inSlide 26: Any Question You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.