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Edit Comment Close Premium member Presentation Transcript Slide 1: PRESENTED BY: NAITIK THAKKAR ( M.PHARM, DEPARTMENT OF PHARMACEUTICS) DHARMAJ DEGREE PHARMACY COLLEGE DDPC GUIDED BY: MR.NISHIT PATEL Assistant Professor DHARMAJ DEGREE PHARMACY COLLEGEINTRODUCTION : INTRODUCTION The study of Spin changes at the nuclear level when radio frequency energy is absorbed in the presence of magnetic field . Measures the absorption of EM radiation in the radiofrequency region 4 MHz to 750 MHz (wavelength 0.4 m to 75 m) Most commonly done on 1 H and 13 C. OBJECTIVES : Structural elucidation Drug design MRISPIN QUANTUM NUMBER: SPIN QUANTUM NUMBER The only nuclei that exhibit the NMR phenomenon are those for which the spin quantum number I is greater than 0. The spin quantum number I is associated with the Atomic number and Mass number of nuclei as followsNUCLEAR ORIENTATION WITH RESPECT TO EXTERNAL MAGNETIC FIELD: Under influence of an external magnetic field, a magnetic nucleus will show different orientations with respect to that field.., No. of possible orientation is given by, For nuclei with I= ½ only two orientations possible, 2* ½+1=2. For nuclei with I=1, three orientations are possible, 2*1+1=3. Spin quantum number of some nuclei NUCLEAR ORIENTATION WITH RESPECT TO EXTERNAL MAGNETIC FIELDNuclear magnetic moment: The Nucleus is charged particle & any moving charge generates a Magnetic Field of its own. Thus, the nucleus has a magnetic moment ( ) generated by its charge & spin. A Hydrogen nucleus may have Clockwise (+ ½ ) or anticlockwise (- ½ ) spin.., And nuclear magnetic moments in this two cases are pointed in opposite directions. Nuclear magnetic moment Aligned Opposed + + +Slide 6: When external magnetic field is applied to the nucleus, protons with their magnetic moment either aliened with the field or opposed to it. Due to this spin states are not of equivalent energy.PRINCIPLE OF NMR : PRINCIPLE OF NMR T o understand principle of NMR we have to understand two theory 1. Quantum Description of NMR : 2. Behavior of Nuclei in Magnetic Field:1. Quantum Description of NMR : According to classical Quantum mechanics, the angular frequency of precession is directly proportional to the applied field & inversely proportional to the angular momentum of the spinning body to which the force is applied. A spinning charged nucleus creates a magnetic field that is analogous to the field produced when electricity flows through a coil of wire. The resulting magnetic moment ( ) is proportional to the angular momentum (m). Thus, Where, proportionality constant γ is the gyromagnetic ratio. It is also defined as., Ratio of the nuclear magnetic moment to the spin quantum number This ratio has a different value for each type of nucleus. 1. Quantum Description of NMR = γ m γ = /IEnergy level in magnetic field: As shown in Figure 1, when a nucleus with a spin quantum number of ½ is brought into an external magnetic field B 0 its magnetic moment (m) or magnetic quantum number becomes oriented in one of two directions (+ ½ or – ½ ) with respect to the field depending on its magnetic quantum State. The potential energy E of a nucleus in these two orientations is given by., The energy for the lower energy m = + ½ state is given by., Energy level in magnetic field E = - mh Bo 2 pSlide 10: E = h Bo 2 p Figure : 1Slide 11: For the m = -1/2 state the energy is Thus, the difference in energy Δ E between the two states is given by Transitions between energy states can be brought about by absorption or emission of electromagnetic radiation of a frequency Vo that corresponds in energy to Δ E. Thus, by substituting the Planck relationship Δ E = hV into above Equation, we obtain the frequency of the radiation required to bring about the transition 2. Behavior of Nuclei in Magnetic Field: : 2. Behavior of Nuclei in Magnetic Field: When the magnetic field is applied, the nucleus, begins to precess about its own axis of spin with angular velocity(ω) because of gyroscopic effect , the force applied to the axis of rotation causes movement not in the plane of the force but perpendicular to this plane; the axis of the rotating particle, therefore, moves in a circular path and the rotation gives angular velocity of this motion w 0. The angular velocity of proton is directly proportional to the strength of the applied field.Slide 13: A Spinning Gyroscope A Spinning Charge in a Gravity Field in a Magnetic FieldSlide 14: The angular velocity of this motion w o , in radians per second, is given by The angular velocity can be converted to the frequency of precession (Vo) known as the Larmor frequency or precession frequency , by dividing with 2 π . Thus, A comparison of Equation of two theory, reveals that the Larmor frequency (Precession) is identical to the frequency of absorbed radiation derived from quantum mechanical considerations . 0 0Slide 16: When the frequency of the oscillating electric field component of the incoming radiation just matches the frequency of the electric field generated by the precessing nucleus, thus causing a spin change. This condition is called resonance or flipping or transition and the nucleus is said to have resonance with the incoming electromagnetic wave. Hence, the technique is termed as.., Nuclear magnetic Resonance Spectroscopy. Saturation and Magnetic Field Strength : The energy difference Δ E between ground state and excited state nuclei is very small. The number of nuclei in the ground state is the number lined up with the magnetic field B 0 . The ratio of excited nuclei to unexcited nuclei is defined by the Boltzmann distribution : where, N0=no. of Unexcited nuclei, N =no. of excited nuclei For a sample at 293 K in a 4.69 T magnetic field, the ratio N/N0 = 0.99997 . There are almost as many nuclei in the excited state as in the ground state because the difference between the two energy levels is very small. This is always the case in NMR; the Boltzmann ratio is always very close to 1.00. For this reason, NMR is inherently a low sensitivity technique . Saturation and Magnetic Field StrengthSlide 18: RELAXATION PROCESS When a nucleus is exposed to radiation of a suitable frequency, absorption occurs because of the slight excess of lower-energy-state nuclei present in the strong magnetic field. This excess is small, so there is always danger that the absorption process will equalize the number of nuclei in the two states and cause the absorption signal to decrease and to approach zero. When this occurs, the spin system is said to be saturated. To avoid saturation, the rate of relaxation of excited nuclei to their lower energy state must be as great or greater than the rate at which they absorb the RF energy.Slide 19: A second factor: Life time of the excited state should be small. These two opposing factors cause the optimal half-life for an excited species to range from about 0.1 to 10 s. There are two important types of relaxation process in NMR spectroscopy. Longitudinal or spin-lattice relaxation. Transverse or spin-spin relaxation(1) Longitudinal or spin-lattice relaxation: (1) Longitudinal or spin-lattice relaxation The entire sample in an NMR experiment, both absorbing and nonabsorbing nuclei, is called the lattice. Spin lattice or longitudinal relaxation involves the transfer of energy from the nucleus in its higher energy state to the molecular lattice i.e. surrounding molecules . A very small increase in sample temperature results on spin–lattice (longitudinal) relaxation. This process is quite fast when the lattice molecules are able to move quickly. This is the state of affairs in most liquid samples.Slide 21: No radiant energy appears ; no other nuclei become excited. Instead, as numerous nuclei lose their energy in this fashion, the temperature of the sample goes up very slightly. Longitudinal relaxation has a relaxation time, T 1 , which depends on the magnetogyric ratio and the lattice mobility. In crystalline solids or viscous liquids T 1 is large because the lattice mobility is low.(2)Transverse or spin-spin relaxation: (2)Transverse or spin-spin relaxation Transverse or spin-spin relaxation is due to mutual exchange of spins by two precessing nuclei, which are in close proximity of each other. An excited nucleus may transfer its energy to an unexcited nucleus nearby. In the process, a proton in the nearby unexcited molecule becomes excited and the previously excited proton becomes unexcited. There is no net change in energy of the system, but the length of time that one nucleus stays excited is shortened because of the interaction.Slide 23: The average excited state lifetime decreases. This type of relaxation is called transverse relaxation or spin–spin relaxation, with a lifetime T 2. It is found in practice that in liquid samples the net relaxation time is comparatively long and narrow absorption lines are observed. In solid samples, however, the transverse relaxation time T 2 is very short.NMR INSTRUMENTATION: The NMR instrument consists: The Magnet Radiofrequency source Sample Holder Amplifier Shim system NMR INSTRUMENTATIONSlide 25: MAGNET Permanent : Constant Bo is generated that is 0.7;1.4;2.1 Adv:- construction is simple cheaper Electromagnet : Bo can be varied which is done by winding the electromagnetic coil around the magnet Most expensive component of the nuclear magnetic resonance spectrometer systemSlide 26: RADIO FREQUENCY SOURCE Used to apply radiofrequency radiation. The radio frequency source is supplied to sample through coils which are wound around sample tube and placed between two poles of magnet. SAMPLE HOLDER It is a Cylindrical glass tube situated between poles of the magnet. 25cm long & 5mm outer diameter. Sample is spun at 30 rpm around its axis to ensure uniform magnetic fieldSlide 27: SHIM COILS The purpose of shim coils on a spectrometer is to correct minor inhomogeneities in the magnetic field (Bo). Location : parallel to magnet face. These inhomogeneities could be caused by the magnet design, materials in the probe, variations in the thickness of the sample tube, sample permeability. A shim coil is designed to create a small magnetic field which will oppose and cancel out an inhomogeneities in the Bo magnetic field.Slide 28: Principle of Instrumental Analysis, Doglos A. Skoog, F.James. Holler, Stanley. R. Crouch, Thomson Book/Cole, Canada, Sixth edition, 2007, p no.551-8. Sharma B.K. Instrumental method of Chemical analysis, P no.619-7. Chatwal GR Anand SK, Instrumental methods of chemical analysis 1 st edition, P no. 2.185-7. Beckett A.H. Stenlake B.J. Practical Pharmaceutical chemistry, part –II,CBS publishers 1 st edition, P no. 408-14. ReferencesSlide 29: THANKS FOR UR PATIENCE You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
NMR intro. by Naitik Thakkar naitik33 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: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 194 Category: Education License: All Rights Reserved Like it (2) Dislike it (0) Added: March 22, 2011 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: pharmaravijo18 (9 month(s) ago) thank you frnd.............. Saving..... Post Reply Close Saving..... Edit Comment Close By: naitik33 (14 month(s) ago) do comment for future improvement... Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Slide 1: PRESENTED BY: NAITIK THAKKAR ( M.PHARM, DEPARTMENT OF PHARMACEUTICS) DHARMAJ DEGREE PHARMACY COLLEGE DDPC GUIDED BY: MR.NISHIT PATEL Assistant Professor DHARMAJ DEGREE PHARMACY COLLEGEINTRODUCTION : INTRODUCTION The study of Spin changes at the nuclear level when radio frequency energy is absorbed in the presence of magnetic field . Measures the absorption of EM radiation in the radiofrequency region 4 MHz to 750 MHz (wavelength 0.4 m to 75 m) Most commonly done on 1 H and 13 C. OBJECTIVES : Structural elucidation Drug design MRISPIN QUANTUM NUMBER: SPIN QUANTUM NUMBER The only nuclei that exhibit the NMR phenomenon are those for which the spin quantum number I is greater than 0. The spin quantum number I is associated with the Atomic number and Mass number of nuclei as followsNUCLEAR ORIENTATION WITH RESPECT TO EXTERNAL MAGNETIC FIELD: Under influence of an external magnetic field, a magnetic nucleus will show different orientations with respect to that field.., No. of possible orientation is given by, For nuclei with I= ½ only two orientations possible, 2* ½+1=2. For nuclei with I=1, three orientations are possible, 2*1+1=3. Spin quantum number of some nuclei NUCLEAR ORIENTATION WITH RESPECT TO EXTERNAL MAGNETIC FIELDNuclear magnetic moment: The Nucleus is charged particle & any moving charge generates a Magnetic Field of its own. Thus, the nucleus has a magnetic moment ( ) generated by its charge & spin. A Hydrogen nucleus may have Clockwise (+ ½ ) or anticlockwise (- ½ ) spin.., And nuclear magnetic moments in this two cases are pointed in opposite directions. Nuclear magnetic moment Aligned Opposed + + +Slide 6: When external magnetic field is applied to the nucleus, protons with their magnetic moment either aliened with the field or opposed to it. Due to this spin states are not of equivalent energy.PRINCIPLE OF NMR : PRINCIPLE OF NMR T o understand principle of NMR we have to understand two theory 1. Quantum Description of NMR : 2. Behavior of Nuclei in Magnetic Field:1. Quantum Description of NMR : According to classical Quantum mechanics, the angular frequency of precession is directly proportional to the applied field & inversely proportional to the angular momentum of the spinning body to which the force is applied. A spinning charged nucleus creates a magnetic field that is analogous to the field produced when electricity flows through a coil of wire. The resulting magnetic moment ( ) is proportional to the angular momentum (m). Thus, Where, proportionality constant γ is the gyromagnetic ratio. It is also defined as., Ratio of the nuclear magnetic moment to the spin quantum number This ratio has a different value for each type of nucleus. 1. Quantum Description of NMR = γ m γ = /IEnergy level in magnetic field: As shown in Figure 1, when a nucleus with a spin quantum number of ½ is brought into an external magnetic field B 0 its magnetic moment (m) or magnetic quantum number becomes oriented in one of two directions (+ ½ or – ½ ) with respect to the field depending on its magnetic quantum State. The potential energy E of a nucleus in these two orientations is given by., The energy for the lower energy m = + ½ state is given by., Energy level in magnetic field E = - mh Bo 2 pSlide 10: E = h Bo 2 p Figure : 1Slide 11: For the m = -1/2 state the energy is Thus, the difference in energy Δ E between the two states is given by Transitions between energy states can be brought about by absorption or emission of electromagnetic radiation of a frequency Vo that corresponds in energy to Δ E. Thus, by substituting the Planck relationship Δ E = hV into above Equation, we obtain the frequency of the radiation required to bring about the transition 2. Behavior of Nuclei in Magnetic Field: : 2. Behavior of Nuclei in Magnetic Field: When the magnetic field is applied, the nucleus, begins to precess about its own axis of spin with angular velocity(ω) because of gyroscopic effect , the force applied to the axis of rotation causes movement not in the plane of the force but perpendicular to this plane; the axis of the rotating particle, therefore, moves in a circular path and the rotation gives angular velocity of this motion w 0. The angular velocity of proton is directly proportional to the strength of the applied field.Slide 13: A Spinning Gyroscope A Spinning Charge in a Gravity Field in a Magnetic FieldSlide 14: The angular velocity of this motion w o , in radians per second, is given by The angular velocity can be converted to the frequency of precession (Vo) known as the Larmor frequency or precession frequency , by dividing with 2 π . Thus, A comparison of Equation of two theory, reveals that the Larmor frequency (Precession) is identical to the frequency of absorbed radiation derived from quantum mechanical considerations . 0 0Slide 16: When the frequency of the oscillating electric field component of the incoming radiation just matches the frequency of the electric field generated by the precessing nucleus, thus causing a spin change. This condition is called resonance or flipping or transition and the nucleus is said to have resonance with the incoming electromagnetic wave. Hence, the technique is termed as.., Nuclear magnetic Resonance Spectroscopy. Saturation and Magnetic Field Strength : The energy difference Δ E between ground state and excited state nuclei is very small. The number of nuclei in the ground state is the number lined up with the magnetic field B 0 . The ratio of excited nuclei to unexcited nuclei is defined by the Boltzmann distribution : where, N0=no. of Unexcited nuclei, N =no. of excited nuclei For a sample at 293 K in a 4.69 T magnetic field, the ratio N/N0 = 0.99997 . There are almost as many nuclei in the excited state as in the ground state because the difference between the two energy levels is very small. This is always the case in NMR; the Boltzmann ratio is always very close to 1.00. For this reason, NMR is inherently a low sensitivity technique . Saturation and Magnetic Field StrengthSlide 18: RELAXATION PROCESS When a nucleus is exposed to radiation of a suitable frequency, absorption occurs because of the slight excess of lower-energy-state nuclei present in the strong magnetic field. This excess is small, so there is always danger that the absorption process will equalize the number of nuclei in the two states and cause the absorption signal to decrease and to approach zero. When this occurs, the spin system is said to be saturated. To avoid saturation, the rate of relaxation of excited nuclei to their lower energy state must be as great or greater than the rate at which they absorb the RF energy.Slide 19: A second factor: Life time of the excited state should be small. These two opposing factors cause the optimal half-life for an excited species to range from about 0.1 to 10 s. There are two important types of relaxation process in NMR spectroscopy. Longitudinal or spin-lattice relaxation. Transverse or spin-spin relaxation(1) Longitudinal or spin-lattice relaxation: (1) Longitudinal or spin-lattice relaxation The entire sample in an NMR experiment, both absorbing and nonabsorbing nuclei, is called the lattice. Spin lattice or longitudinal relaxation involves the transfer of energy from the nucleus in its higher energy state to the molecular lattice i.e. surrounding molecules . A very small increase in sample temperature results on spin–lattice (longitudinal) relaxation. This process is quite fast when the lattice molecules are able to move quickly. This is the state of affairs in most liquid samples.Slide 21: No radiant energy appears ; no other nuclei become excited. Instead, as numerous nuclei lose their energy in this fashion, the temperature of the sample goes up very slightly. Longitudinal relaxation has a relaxation time, T 1 , which depends on the magnetogyric ratio and the lattice mobility. In crystalline solids or viscous liquids T 1 is large because the lattice mobility is low.(2)Transverse or spin-spin relaxation: (2)Transverse or spin-spin relaxation Transverse or spin-spin relaxation is due to mutual exchange of spins by two precessing nuclei, which are in close proximity of each other. An excited nucleus may transfer its energy to an unexcited nucleus nearby. In the process, a proton in the nearby unexcited molecule becomes excited and the previously excited proton becomes unexcited. There is no net change in energy of the system, but the length of time that one nucleus stays excited is shortened because of the interaction.Slide 23: The average excited state lifetime decreases. This type of relaxation is called transverse relaxation or spin–spin relaxation, with a lifetime T 2. It is found in practice that in liquid samples the net relaxation time is comparatively long and narrow absorption lines are observed. In solid samples, however, the transverse relaxation time T 2 is very short.NMR INSTRUMENTATION: The NMR instrument consists: The Magnet Radiofrequency source Sample Holder Amplifier Shim system NMR INSTRUMENTATIONSlide 25: MAGNET Permanent : Constant Bo is generated that is 0.7;1.4;2.1 Adv:- construction is simple cheaper Electromagnet : Bo can be varied which is done by winding the electromagnetic coil around the magnet Most expensive component of the nuclear magnetic resonance spectrometer systemSlide 26: RADIO FREQUENCY SOURCE Used to apply radiofrequency radiation. The radio frequency source is supplied to sample through coils which are wound around sample tube and placed between two poles of magnet. SAMPLE HOLDER It is a Cylindrical glass tube situated between poles of the magnet. 25cm long & 5mm outer diameter. Sample is spun at 30 rpm around its axis to ensure uniform magnetic fieldSlide 27: SHIM COILS The purpose of shim coils on a spectrometer is to correct minor inhomogeneities in the magnetic field (Bo). Location : parallel to magnet face. These inhomogeneities could be caused by the magnet design, materials in the probe, variations in the thickness of the sample tube, sample permeability. A shim coil is designed to create a small magnetic field which will oppose and cancel out an inhomogeneities in the Bo magnetic field.Slide 28: Principle of Instrumental Analysis, Doglos A. Skoog, F.James. Holler, Stanley. R. Crouch, Thomson Book/Cole, Canada, Sixth edition, 2007, p no.551-8. Sharma B.K. Instrumental method of Chemical analysis, P no.619-7. Chatwal GR Anand SK, Instrumental methods of chemical analysis 1 st edition, P no. 2.185-7. Beckett A.H. Stenlake B.J. Practical Pharmaceutical chemistry, part –II,CBS publishers 1 st edition, P no. 408-14. ReferencesSlide 29: THANKS FOR UR PATIENCE