Chemical Reactions
Chapter Name : Haloalkanes And Haloarenes |
Sub Topic Code : 102_12_10_06_01 |
Topic Name : Chemical Reactions |
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Sub Topic Name : Reactions Of Haloalkanes |
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Introduction
• The reactions of haloalkanes may be divided into the following categories: • (i) Nucleophilic substitution - In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen. • A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction. • (ii) Elimination reactions - When a haloalkane with b-hydrogen atom is heated with alcoholic solution of potassium hydroxide, there is elimination of hydrogen atom from b-carbon and a halogen atom from the a-carbon atom. • As a result, an alkene is formed as a product. Since b-hydrogen atom is involved in elimination, it is often called b-elimination. • (iii) Reaction with metals - Most organic chlorides, bromides and iodides react with certain metals to give compounds containing carbon-metal bonds. • Such compounds are known as organo-metallic compounds.
Pre-Requisites:
Elements, bond, halides
Activity:
• Synthetic halogen compounds, viz. • chloroquine is used for the treatment of malaria; • Halothane is used as an anaesthetic during surgery.
Real Life Question:
What are haloarenes and haloalkanes?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| - Haloalkanes - Haloarenes | • Haloalkanes contain halogen atom(s) attached to the sp3 hybridised carbon atom of an alkyl group. • Haloarenes contain halogen atom(s) attached to sp2 hybridised carbon atom(s) of an aryl group. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| • Chlorine containing antibiotic, chloramphenicol, produced by soil microorganisms is very effective for the treatment of typhoid fever. |
Real life uses :
• Synthetic halogen compounds, viz. ? chloroquine is used for the treatment of malaria; ? Halothane is used as an anesthetic during surgery..
Places to visit :
Pharmacy.
Practical examples around us
| Examples | Explainations |
|---|---|
| • Synthetic halogen compounds, viz. ? chloroquine is used for the treatment of malaria; ? Halothane is used as an anesthetic during surgery. |
What you learn in Theory:
• The reactions of haloalkanes may be divided into the following categories: • (i) Nucleophilic substitution - In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen. • A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction. • (ii) Elimination reactions - When a haloalkane with b-hydrogen atom is heated with alcoholic solution of potassium hydroxide, there is elimination of hydrogen atom from b-carbon and a halogen atom from the a-carbon atom. • As a result, an alkene is formed as a product. Since b-hydrogen atom is involved in elimination, it is often called b-elimination. • (iii) Reaction with metals - Most organic chlorides, bromides and iodides react with certain metals to give compounds containing carbon-metal bonds. • Such compounds are known as organo-metallic compounds.
What you learn in Practice:
• Haloalkanes and Haloarenes are classified based on the number of halogen compounds contained in them.