Stereochemistry (Part-1) PDF

Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I Stereochemistry (Part-1) Prof. Dr. Mostafa El-Miligy Professor of Pharmac...

Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I Stereochemistry (Part-1) Prof. Dr. Mostafa El-Miligy Professor of Pharmaceutical Chemistry Faculty of Pharmacy Alexandria University 1 Definition: Stereochemistry is the chemistry of molecules in three dimensions. 2 Stereochemistry (Part-1) 1 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I Isomers: Compounds with the same molecular formula but different structures are called isomers. 3 Example: 1-butene and 2-butene have the same molecular formula, C4H8, but structurally they are different because of the different positions of the double bond. 4 Stereochemistry (Part-1) 2 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I Types of isomer: I-Constitutional (Structural) isomers. II-Stereoisomers. Types of Stereoisomers: A-Conformational isomers: B-Configurational isomers: Configurational isomers include: Enantiomers Optical isomers Diastereomers Geometrical isomers 5 I-Constitutional (Structural) isomers They are compounds have: The same molecular formula. Differ in the nature or sequence of bonding. They are subdivided into 3 classes: a-Chain isomers b-Positional isomers c-Functional group isomers 6 Stereochemistry (Part-1) 3 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I a-Chain isomers They differ in the arrangement of carbon atoms. E.g. n-butane and isobutane n-pentane, isopentane and neopentane 7 b- Positional isomers They differ in the position of substituent. E.g. n-propanol and isopropanol 8 Stereochemistry (Part-1) 4 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I c- Functional group isomers They differ in the functional group. E.g. Ethanol and dimethyl ether 9 II-Stereoisomers They are compounds with their atoms connected in the same order but they differ in the three-dimensional arrangements of groups or atoms in space. 10 Stereochemistry (Part-1) 5 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I II-Stereoisomers A-Conformational isomers: Atoms within a molecule move relative to one another by rotation around single bonds. 11 Visualization of conformers 12 Stereochemistry (Part-1) 6 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I 13 Example: n-Butane Energy changes that arise from rotation about the C2–C3 bond of butane 14 Stereochemistry (Part-1) 7 Prof. Dr. Mostafa El-Miligy Pharmaceutical Organic Chemistry I Exception is 2-fluoroethanol which exists predominantly in gauche conformation due to intra-molecular hydrogen bonding (Restricted rotation). 15 Thank you Happy Studies 16 Stereochemistry (Part-1) 8