Chapter 16, plane polarized light lec.11

Dr. Tariq Zaman is a chemistry lecturer in Khyber Pakhtunkhwa, Pakistan

1. Optical Activity When a compound rotate the plane Polarized Light than it is said to be optically active and this phenomenon is called optical activity. 1. Dextrorotatory Isomer (+ compound): A compound is said to be dextrorotatory when it rotate plane Polarized Light on right side. Dextro means right hand. 2. Levororatory Isomer (- compound): A compound is said to be levorotatory when it rotate plane Polarized Light on left side. Levo means left hand. Page 139

2. Chirality Optical Activity in Glucose * *

3. Light that vibrates in one plane is called as Plane Polarized Light Light can be divided into two types according to wavelength. Polychromatic Light : Light that composed of many wavelengths are called as polychromatic light. All lights Gamma, X-rays, UV, IR are polychromatic light. Monochromatic Light : Light that composed of a single wavelength is called as monochromatic light. Monochromatic light can be selected for studying of properties of compounds. For example optical activity. Page 139

4. Polarimeter An instrument that is used for the measurement of optical activity of a compound is called as polarimeter Page 139,140

5. Plane polarizer are mostly Nicol Prism made up of calcite (CaCO 3 ) Dextrorotatory Levorotatory

6. 2. Optical Isomerism Optical Isomers : Different compounds that are mirror images of each other and non superimposable are called as optical isomers. These isomers are formed due to rotation of Plane Polarized Light either clockwise Dextrorotatory or anti clockwise Levororatory . These isomers have chiral (asymmetric) carbon atom. Chiral Carbon ( Chiral centre) Carbon that attaches with four different atoms (groups) is called chiral (asymmetric)carbon. Chiral means handedness Page 140

7. Chiral Compounds are mirror images of each other Page 140

8. Chiral means hand like property. As left hand is mirror image of right hand, similarly Chiral molecules are mirror images of each other

9. Two types of Lactic Acids ( Dextrorotatory(d) Levorotatory(l) Optical Isomers are also called as Enantiomers

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