Introduction to Geometrical Isomerism.pptx

Introduction to Geometrical Isomerism

1. Introduction to Geometrical Isomerism Geometrical isomerism, also known as cis-trans isomerism, is a type of stereoisomerism that arises when a molecule contains a rigid, planar structure with restricted rotation around a carbon-carbon double bond. This results in the possibility of different spatial arrangements of the substituents.

2. Definition of Geometrical Isomerism Geometrical isomerism occurs when two molecules have the same molecular formula and connectivity, but differ in the spatial arrangement of their substituents around a carbon-carbon double bond. This results in distinct physical and chemical properties between the isomers.

3. Conditions for Geometrical Isomerism 1 Rigid, Planar Structure The molecule must have a carbon-carbon double bond with a rigid, planar structure that prevents free rotation. 2 Different Substituents The two substituents attached to each carbon of the double bond must be different. 3 Restricted Rotation The rotation around the carbon-carbon double bond must be restricted, preventing the substituents from switching positions.

4. Types of Geometrical Isomers Cis Isomers In cis isomers, the same substituents are on the same side of the double bond. Trans Isomers In trans isomers, the same substituents are on opposite sides of the double bond. E-Z Isomers E-Z isomerism is a system used to designate the stereochemistry of organic compounds with a carbon-carbon double bond.

5. Cis-Trans Isomerism 1 Cis Isomers In cis isomers, the substituents are on the same side of the double bond. 2 Trans Isomers In trans isomers, the substituents are on opposite sides of the double bond. 3 Interconversion Cis-trans isomers cannot be interconverted without breaking the double bond.

6. E-Z Isomerism Priority Groups E-Z isomerism considers the priority of the substituents attached to the carbon-carbon double bond. Directional Orientation The substituents are assigned E (from the German "entgegen") or Z (from the German "zusammen") based on their relative positions. Double Bond Geometry E isomers have the higher priority substituents on opposite sides, while Z isomers have them on the same side.

7. Factors Affecting Geometrical Isomerism Steric Hindrance Large substituents on the carbon-carbon double bond can cause steric hindrance, favoring the trans isomer. Electronegativity The relative electronegativity of the substituents can also influence the stability and formation of the isomers. Solvent Effects The polarity of the solvent can affect the solubility and stability of the isomers, potentially shifting the equilibrium.

8. Importance and Applications of Geometrical Isomerism Pharmaceutical Industry Geometrical isomerism is crucial in the development of new drugs, as the isomers can have vastly different biological activities. Materials Science Geometrical isomers can exhibit different physical properties, such as melting and boiling points, which is important in the design of new materials. Organic Synthesis Understanding and controlling geometrical isomerism is essential in the synthesis of complex organic molecules with desired properties. Environmental Impact Geometrical isomers can have different environmental impacts, such as toxicity and biodegradability, which is important in environmental chemistry and regulation.