IR and NMR spectroscopy
•Transferir como PPTX, PDF•
72 gostaram•27,290 visualizações
presentation on absorption spectroscopy
Recomendados
Mais conteúdo relacionado
Mais procurados
Mais procurados (20)
Semelhante a IR and NMR spectroscopy
Semelhante a IR and NMR spectroscopy (20)
Último
Último (20)
IR and NMR spectroscopy
- 1. Presented by: Asif Mohammad Salehin Jatan Tanchangya Sulov Saha Md. Mohsin Ali
- 2. Spectroscopy Definition: Spectroscopy is the study of of the interaction between matter and electromagnetic radiation. Types of spectroscopy: • Absorption spectroscopy – uses electromagnetic spectra in which a substance absorbs: IR, NMR • Emission spectroscopy – uses electromagnetic spectra in which a substance emits: Luminescence • Scattering spectroscopy – measures the amount of light that a substance scatter at certain wavelengths, incident angles and polarization angles: Raman
- 3. Infrared Spectroscopy • IR spectroscopy is concerned with the study of absorption of infrared radiation, which causes vibrational transition in the molecule. • IR spectra mainly used to identify functional groups present in molecules.
- 5. Principle of IR spectroscopy • Molecules are made up of atoms linked by chemical bonds. The movement of atoms and the chemical bonds like spring and balls (vibration). • This characteristic vibration are called Natural frequency of vibration.
- 6. • When energy in the form of infrared radiation is applied then it causes the vibration between the atoms of the molecules and when, Applied infrared frequency = Natural frequency of vibration Then, absorption of IR radiation takes place and a peak is observed. Different functional groups absorb characteristic frequencies of IR radiation. Hence gives the characteristic peak value. Therefore, IR spectrum of a chemical substance is a finger print of a molecule for its identification.
- 7. Criteria for a compound to absorb IR radiation • Correct wavelength of radiation A molecule to absorb IR radiation, the natural frequency of vibrations of some part of a molecule is the same as the frequency of incident radiation. • Change in dipole moment A molecule can only absorb IR radiation when its absorption cause a change in its electric dipole.
- 8. Types of Molecular Vibrations 1.Stretching Symmetrical Asymmetrical 2.Bending In plane Out plane
- 9. a) Symmetrical stretching: 2 bonds increase or decrease in length simultaneously. H H C
- 10. b) Asymmetrical stretching: In this, one bond length is increased and other is decreased. H H C
- 11. a) In plane bending: i. Scissoring ii. Rocking
- 12. b) Out plane bending: i. Wagging ii. Twisting H H CC H H CC
- 13. Instrumentation
- 14. Interpreting an Infrared Spectrum • Ethanoic acid (it contains C-C, C-H, C=O, C-O and O-H bonds.)
- 15. Fig: IR Spectra of common functional groups
- 16. Applications • Identification of functional group and structure elucidation • Identification of substances • Studying the progress of the reaction • Detection of impurities • Quantitative analysis
- 17. Pros and Cons of IR Spectroscopy Largely qualitative Difficult to analyze complex solutions in infrared Similar infrared spectra can misidentify the fingerprint region
- 18. NMR Spectroscopy The study of absorption of radiofrequency radiation by nuclei in a magnetic field is called Nuclear Magnetic Resonance. • NMR spectroscopy is commonly used technique for organic compound structure determination.
- 20. Principle of NMR spectroscopy • A spinning charge creates a magnetic moment, so these nuclei can be thought of as tiny magnets. • If we place these nuclei in a magnetic field, they can line up with or against the field by spinning clockwise or counter clockwise.
- 21. NMR active nuclei Number of nucleons -Must be odd for residual magnetism For e.g. Hydrogen exhibits, Deuterium does not 1H, 13C and 15N nuclei -have a very small magnetic moment: “half integer spin”
- 22. Resonance condition •Transition from low to high energy state occurs • hﬠ = gßH •Either a constant magnetic field is applied and appropriate region of radio frequency is swept •Or a constant frequency is employed & the external magnetic field is swept
- 23. Chemical shifts - Arises from applied field inducing secondary fields at the proton by interacting with adjacent bonding electrons - Is measured in ppm relative to an internal standard – TMS - Trimethylsilane (TMS) is the accepted internal standard for calibrating chemical shift for 1H, 13C and 29Si NMR spectroscopy in organic solvents. H 3.6 ppm 1.2 ppm
- 24. Splitting or Multiplicity Scalar coupling constants - Protons on adjacent carbons will interact and “split” each others resonances into multiple peaks (multiplets) - Measured in Hz (“Hertz”, s-1) - Caused by different spin states of neighboring spins (parallel or antiparallel) H - Equivalent protons do not show spin-spin coupling - Doublet: 1 coupling partner - Triplet: 2 coupling partners - Quartet: 3 coupling partners
- 25. When energy in the form of radiofrequency is applied When applied frequency is equal to processional frequency Absorption of energy occurs Nucleus is in resonance NMR signal is recorded Steps involved in the process
- 26. Instrumentation
- 27. • Fourier Transform NMR Instrument • Continuous Wave NMR Instrument Two types of NMR spectroscopy instruments
- 29. Study of 1H NMR Spectra
- 31. Interpretation of NMR Spectrum Number of main signal = number of equivalent protons in unknown compound Chemical shift indicates the type of H atoms. E.g. methylene, methyl groups, etc. Spin-spin splitting ---- arrangement of groups in the molecule. Area of peaks ---- no. of H nuclei present in each group. For e.g. relative areas of methyl peaks in propane would be 6:2. In butane it would be 6:4
- 32. E.g. of ethanol a) Low resolution spectrum b) High resolution spectrum
- 33. Applications • To study molecular structure and interactions • For determining 3D structure of proteins and other macromolecules • Solid-state NMR is used to study variety of materials • Magnetic Resonance Imaging (MRI) • Oil and natural gas exploration • Polymer production, cosmetics and food manufacturing
- 35. MRI Eliminates risk of X-radiation Excellent and contrast resolution Detecting disease at earlier stages Magnetic resonance imaging (MRI) is a noninvasive medical test that physicians use to diagnose and treat medical conditions.
- 36. Pros and Cons of NMR Spectroscopy Provides high resolution information Does not require a protein crystal and is not affected by crystal contacts Can be used to study flexible proteins Reflects conformational averaging Requires high concentrations of soluble protein Can not be applied to large proteins (800kD max so far) Can not be used with amyloid fibrils
Notas do Editor
- Spectroscopy is a scientific measurement technique. It measures light that is emitted, absorbed, or scattered by materials and be used to study, identify and quantify those materials. In this presentation, we are going to cover IR and NMR spectroscopy from the absorption spectroscopy respectively.
- The major use of radio waves is in NMR spectroscopy. That works because some atomic nuclei exhibit ‘nuclear spin’.
- Alpha spin state - favorable, lower energy and anticlockwise Beta spin state - unfavorable, higher energy and clockwise Bo – constant magnetic field produced by the large magnet
- Here comes the process of NMR spectroscopy in a simpler terms.
- This is the basic model of a NMR spectrophotometer.
- In Fourier Transform NMR Instrument small energy change takes place in the magnitude, present in NMR and hence the sensitivity of this instrument is very less. The Continuous Wave NMR follows the principle of optical spectrometers. The pulsed FT-NMR is much faster as compared to continuous wave NMR.
- 1H NMR is used to determine the type and number of H atoms in a molecule.
- 13C NMR is used to determine the type of carbon atoms in the molecule. Carbon NMR is simpler than proton NMR because of the carbon NMR has large chemical shift ranging as much as 200 ppm; while for proton NMR, it is not more than 10ppm.