Some possible Revision Notes for the chapter "Haloalkanes and Haloarenes" in Class 12 Chemistry are:
Introduction:
• Haloalkanes are organic compounds in which one or more hydrogen atoms have been replaced by halogen atoms (fluorine, chlorine, bromine, or iodine) while in Haloarenes, halogen atoms are attached to an aromatic ring.
• They are used as solvents, refrigerants, and pesticides.
• They can have different physical and chemical properties as compared to their parent alkanes and are, hence, utilized in many industrial processes.
Classification of Haloalkanes:
• They are classified according to the number of halogen atoms present - mono, di, tri, tetra, or polyhaloalkanes.
• They can be further classified as primary, secondary, or tertiary based on the number of carbon atoms attached to the alpha-carbon of the halogen.
• They can also be classified as allylic, benzylic, or vinylic based on where the halogen is attached.
Physical Properties of Haloalkanes:
• They have a higher boiling point than their parent alkanes as they have a higher dipole moment due to the presence of halogen atoms.
• Their melting and boiling points increase with the increase of halogen atoms in the molecule.
• They have low solubility in water but are soluble in non-polar solvents.
Chemical Properties of Haloalkanes:
• They undergo nucleophilic and elimination reactions.
• Nucleophilic substitution reactions occur when a nucleophile attacks the alpha-carbon atom and replaces the halogen atom.
• Elimination reactions occur when a strong base removes a hydrogen atom and a halogen atom from adjacent atoms, leading to the formation of an alkene.
• The rate of nucleophilic substitution reactions is affected by the strength of the nucleophile, the type of halogen, and the type of carbon-halogen bond.
Classification of Haloarenes:
• They are classified according to the number of halogen atoms present - mono, di or polyhaloarenes.
• They can be further classified as ortho, meta, or para depending on the position of the halogen atom on the ring.
Physical Properties of Haloarenes:
• They have a higher boiling point than their parent benzene due to the presence of halogen atoms which increase the dipole moment.
• Their melting and boiling points increase with the increase of halogen atoms in the molecule.
• They are insoluble in water but are soluble in non-polar solvents.
Chemical Properties of Haloarenes:
• They undergo nucleophilic substitution reactions but not elimination reactions due to the stability of the aromatic ring.
• The rate of nucleophilic substitution reactions is affected by the type of halogen and the position of the halogen on the ring.
Uses of Haloalkanes and Haloarenes:
• They are used as solvents, refrigerants, and pesticides.
• Polychlorinated biphenyls (PCBs) are chlorinated hydrocarbons used in electrical insulators.
• Chlorofluorocarbons (CFCs) are used in refrigeration and air conditioning.
Environmental Impact of Haloalkanes and Haloarenes:
• They are persistent organic pollutants and can cause harm to the environment and human health.
• CFCs have been found to contribute to the depletion of the ozone layer and are banned in many countries.
• PCBs have been linked to cancer and other health problems and are also banned in many countries.
Conclusion:
Haloalkanes and Haloarenes have many industrial applications but their persistence in the environment can cause harm to human health and the ecosystem, and hence, their use must be strictly regulated.
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Revision Notes for Alcohol, Phenol and Ether
Revision Notes for Aldehydes, Ketones and Carboxylic Acids
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