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- 1. Infrared spectroscopy Presented by: Zaima Khan Roll number:014 Department:Adv.Biological techniques
- 2. General view of spectroscopy • Spectroscopy is the branch of science in which we study about the interaction of electromagnetic radiations with matter in order to determine its structure. • Spectrometer: The instrument which is widely used for spectroscopic analysis of sample. • Spectrum: The data which is obtained from spectroscopy is called spectrum. It is a plot which shows the relation between the intensity of energy and the wavelength( frequency, wavenumber). • Types: UV spectroscopy • Infrared spectroscopy • X-ray spectroscopy
- 3. Infrared spectroscopy • It is a technique which is used for the identification of functional group of different chemical compounds on the basis of interaction of electromagnetic radiations of particular wavelength • Infrared spectroscopy has proved to be a powerful tool for the study of biological molecules, including proteins, lipids, carbohydrates, and nucleic acids. • In electromagnetic spectrum,the infrared radiations lies between visible and microwave region and have longer wavelength than visible and shorter wavelength than microwave region. • IR radiations has wavelengths λ between 760 nm and 1 mm, which corresponds to a frequency range from 300 GHz to 400 THz.
- 4. Infrared radiations • Infrared region refers to the part of electromagnetic spectrum between visible and microwave region.
- 5. Why we use infrared spectroscopy? • The most important function of IR spectroscopy is the identification of functional group e.g. hydroxyl (OH) is the functional group of alcohol the functional group in aldehyde is -CHO. in ketones is -CO-, in Carboxylic acids is -COOH. • Detection of impurities e.g. presence of cyclohexane in cyclohexanol • Used to check out the progress of reaction e.g. oxidation of 2° alcohol to ketone • Identification of geometric isomers e.g. cis-spectra id different from trans
- 6. Cont.…... • Presence of water molecules e.g.( water present in the form of ligands give different IR- spectrum than that of lattice water molecules) • For the analysis of drugs • IR-spectroscopy is widely used in both research and industry. • It is applied in for detection and identification of different compounds in solving problems in the field of forensics, medicines, oil industry, atmospheric chemistry, pharmacology, etc. • Why we call it infrared spectroscopy? • It is a spectroscopic method in which the electromagnetic radiations are in the infrared range of electromagnetic spectrum. • Infrared range includes wavenumber; 5000 to 6670cm-1 and wavelengths range from about 700 nanometers (nm) to 1 millimeter (mm).
- 7. Basic Principle • Molecules are made-up of atoms which are linked by bonds. Molecules absorb specific frequencies that are characteristics of their structure. At ordinary temperature, all molecules are naturally in state of vibrational motion(like ball and spring). • Due to this characteristic vibrational motion IR spectroscopy is called vibrational spectroscopy.
- 8. Conti….. • The IR spectrum of a sample is recorded by passing a beam of IR radiations through the sample by radiance source. • When light of different wavelength falls on a sample then the interatomic bonds absorb the energy of IR radiations then they show vibrational motion. • Then we examined the transmitted light by detector which shows that how much energy is absorbed at each frequency. • Photons energy associated with infrared region is not enough to excite electrons but causes the vibrational motion of covalently bonded atoms.
- 9. Modes of vibration • When molecules absorb specific IR radiations, it must undergo a net change in dipole moment as a result of vibrational or rotational motion. And when IR radiation passed, the vibrational motion of molecules are increased. • Vibrational motion is divided into two major types depend on the length of bond or angle is changing; 1. Stretching motion 2. Bending motion
- 10. Stretching motion • In these vibrations, the distance between two atoms increase or decrease but the atoms remain in same bond axis. 1. Symmetric vibration: In this type, atoms of molecule move away or towards the central atom in the same direction. 2. Asymmetric vibration: In this type, one atom approach central atom and other atom departs from it.
- 11. Bending motion • The position of atoms change with respect to bond axis or molecular vibration due to change in angles. • There are four types of bending motion: 1. Scissoring: In this type, two atoms approach each other 2. Rocking: The movement of molecules in the same direction. 3. Wagging: The two atoms move up and down the plane with respect to central atom. 4. Twisting: one atom moves up the plane while the other move down the plane with respect to central atom.
- 13. Instrumentation of infrared spectroscopy An infrared spectrophotometer is an instrument that passes infrared light through an organic molecule and produces a spectrum . The principal components of IR the spectrometer are: • Radiation source(Tungsten lamp, Mercury arc) • Sample cells and sampling of substances • Monochromators(Prism, filter) • Detectors-measure the strength of the IR radiation • Recorder-capture all aspects of the IR spectrum. This instrumentation involves the gathering of absorption data and the analysis of that information as an IR spectrum.
- 14. IR spectrometer
- 16. IR Regions • During the analysis of spectrum, two regions are observed in Infrared absorption spectra; 1. Functional group region 2. Fingerprint region • The functional group region runs from 4000 cm-1lto 1450 cm-1, and the fingerprint region from 1450 cm-1to 500 cm-1. • The functional group region contains relatively few peaks. • While in fingerprint region, the pattern of peaks is more complicated
- 18. Functional Region • IR (infrared) spectroscopy is useful in organic chemistry because it enables you to identify different functional groups in functional region. • Each functional group contains certain bonds which absorb radiations of different wavelength and produces different bond absorption at different locations and intensities on IR spectrum. • Recognizing where the absorptions generated by the common functional groups occur will help you to interpret IR spectra. • This table lists the locations and intensities of absorptions produced by typical functional groups.
- 20. Fingerprint region • This region can be used to identify unknown or two different organic compounds by comparing the spectroscopy graph. • In this region small difference in the structure and constitution of a molecule result significant change in absorption band and many compound show unique absorption band in this region which is useful for identification of compound • It consist of: • Region 1500-1350cm-1 appearance of duplet near 1380cmand 1365cm-1 show the appearance of 3 degree butyl group. • Region 1350cm 1000cm-1 all classes of compound i.e. alcohol, Easter, lactones, show absorption in this region due to see C-H stretching. • Region below 1000cm-1 distinguish between cis and trans alkenes.
- 21. • Compare the IR spectra of propan-1-ol and propan-2-ol
- 22. • Both spectra are quite similar in the functional group region, but their absorption patterns in the fingerprint region are completely different.