CHROMOPHORES

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Chromophoreand their interactions with Electro Magnetic Radiation : 

Chromophoreand their interactions with Electro Magnetic Radiation Vamsi krishna Dept. Of Pharmaceutics

Chromophore and their interactions with Electro Magnetic Radiation : 

Introduction Definition Types of chromophores Auxochrome Types of Shifts Examples Effect of conjugation Solvent effect Contents Chromophore and their interactions with Electro Magnetic Radiation

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation It is a Greek word. Chroma ="color“ and phoros ="bearer“)……. Introduction

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Definition: any group which exhibits the absorption of EMR in UV or visible region. Compound containing chromophore is CHROMOGEN Eg: C=C, C=O, NO2 What it is?

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Independent chromophores Eg: AZO groups Dependent chromophores Eg: Acetone having one ketone group is colorless whereas diacetyl having two ketone groups is yellow. Types of Chromophore

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation A saturated group with non bonding electrons when attached to chromophore altering both wavelength as well as intensity of absorption. Eg: OH, NH2, NHR. Auxochrome Intensity

Chromophore and their interactions with Electro Magnetic Radiation : 

bathochromic hypsochromic hyperchromic hypochromic 200 wavelength 800 absorbance λ max Chromophore and their interactions with Electro Magnetic Radiation

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Bathochromic shift is produced when 2 or more chromophores are present in conjugation in a molecule Eg: ethylene shows max. Absorbance at 170 nm whereas 1,3-butadiene shows max. Absorbance at 217nm Bathochromic shift

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation It is caused by removal of conjugation in system or by change of solvent Eg: Aniline shows max. absorbance at 280nm.In acidic solution, blue shift occurs and the max. absorbance is seen at 200nm. Hypsochromic shift

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Hyperchromic shift is usually caused by introduction of auxochrome. Eg: Introduction of methyl group at second position of pyridine increases max. intensity from 2750 to 3560. Hyperchromic shift

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Hypochromic shift is usually brought by groups which are able to distort the geometry of the molecule. Eg: Introduction of methyl group at second position of bi phenyl group produces hypochromic shift which occours due to the distortion of the methyl group. Hypochromic shift

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation As the number of double bonds increases, the absorbance moves to longer wavelength Eg: Butadiene (CH2=CH-CH=CH2)In hexane solution exhibits max.absorbance at 270nm whereas in 1,3,5,7 octatetraene (CH2=CH-CH=CH-CH=CH- CH=CH2 ) in hexane exhibits max absorbance at 296nm. Effect of conjugation

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Important role in the varying the absorbances of different compounds. Thus solvent selection is very important and solvents having the double and triple bonds are to be avoided. Eg: S,Br,I. Typical solvents are to be used.Eg:water, ethanol, hexane, cyclohexane. Solvent effects

Chromophore and their interactions with Electro Magnetic Radiation : 

Chromophore and their interactions with Electro Magnetic Radiation Instrumental methods of chemical analysis. Gurudeep R.Chatwal and sham K. Anand. (pg.no 2.156 to 2.161) Text book of analytical chemistry by Y.Anjaneyulu and chandra sekhar. Introduction to spectroscopy by Pavia. Lampman. Kriz (pg .no 359 to 360). References

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