JSPM’S Charak College Of Pharmacy & Research
Gat no.720/1&2,Wagholi, Pune-Nagar Road,Pune-412207
seminar on Structural Elucidation by UV Spectrophotometry
Presented By, Guided By, Miss. Poonam More Dr. Rajesh J Oswal
Prof. Sandip Kshirsagar
Department of Pharmaceutical Chemistry
What do you mean by Structure Elucidition
Structural elucidation is the determination of the chemical structure of chemically uncharacterised substances such as natural products. It is preceded by the extraction and isolation steps. It makes use of various chromatography techniques (MPLC, HPLC) as well as spectrometric techniques (MS, 1D and 2D NMR[1]). MS spectrometers like ions traps can use the fragmentation techniques to further investiguate the structure of the molecule.It is a technique used notably in phytochemistry, for instance to characterise polyphenol oxidation products.
INTRODUCTIONSpectroscopic methods are the main tool of modern chemistry for the identification of molecular structures, to monitor reactions and to control the purity of compounds, most essential methods for the organic chemistry are the Nuclear Magnetic Resonance (proton) ,Nuclear Magnetic Resonance( C13) ,Infrared Spectroscopy , Mass spectroscopy , UV Visible spectroscopy
Proton Neuclear Magnetic resonance
In proton NMR spectroscopy determine the number of Hydrogen atom present in the molecule by using n+1 rule.
Infrared SpectroscopyUsing IR spectroscopy determine the what type of functional group present in the molecule.
Mass SpectroscopyMass spectroscopy determine the molecular weight of the molecule.
Molecular weights of compounds can be measured spectrophotometrically by preparing the suitable derivatives of these compounds.For example, if we want to determine the molecular weight of amine then it is converted in to amine picrate. Then known concentration of amine picrate is dissolved in a litre of solution and its optical density is measured at λmax 380 nm. After this the concentration of the solution in gm moles per litre can be calculated by using the following formula.
"c" can be calculated using above equation, the weight "w" of amine picrate is known. From "c" and "w", molecular weight of amine picrate can be calculated. And the molecular weight of picrate can be calculated using the molecular weight of amine picrate.
By using these above spectroscopy we find out the strcture of molecule . After knowning the strcture of molecule apply the UV spectrophotometry for measurement of avelength maximum.
UV SpectrophotometryWe will find that the effect of substituent groups
can be reliably quantified from empirical observation of known conjugated structures and
applied to new system.
This quantification is referred to as the Woodward-Fieser Rules which we will apply to
three specific chromophores: 1.Conjugated dienes
2.Conjugated dienones 3.Aromatic systems
Beers Lambert’s LawBY using Beer Lambert’s Law determine the concentration of chromophoric group present in molecule.
References1. William Kemp: Organic Spectroscopy, third
edition, published by Palgrave, New York,1991,56,57,171-181.
2. Pavia D.L.,Lampman G.M., Kriz G.S., Vyvyan J.R.,: Spectroscopy, India Edition, published by Cengage Learning,2007,125,126.
3. Skoog D.A., Holler F.J., Nieman T.A.,: Principles of Instrumental Analysis, fifth edition, published by Thomson,2003,498
4. www.google.co.in.
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