Halogen Derivatives Preparation and Properties
Introduction :
→ The replacement of one or more hydrogen atoms of a aliphatic or aromatic, hydrocarbon by an equal number of halogen atoms results in the formation of haloalkane (or alkyl halide) and haloarene (or aryl halid) respectively.
- Haloalkane : RX where R is alkyl group
- Haloarne : ArX where Ar ja aryl group.
X is halogen atom (P, Cl, Br, I).
Thus, haloalkanes and haloarenes are halogen derivatives of aliphatic and aromatic hydrocarbons.
The general formula of haloalkane is Cn H2n+1X or RX,
where X = halogen atom (F, Cl, Br, I) and n = 1, 2, 3
Haloalkanes contain halogen atom(s) attached to the sp3 hybridised carbon.
Summary of the chapter and glossary
→ Classification of halogen derivation:
- Due to difference in electronegativity of carbon and halogen, C-X bond is polar (C-X) in halogen derivatives.
Main reactions of alkyl halides are nucleophilic substitution reactions which are classified as SN1 and SN2. - Aryl halides mainly gives electrophilic and nucleophilic substitution reactions.
- Due to resonance in aryl halide there is partial double bond character in C-X bond. Therefore, nucleophilic substitution reaction does not take place easily.
- In electrophilic substitution reactions of aryl halides, halogen atom is ortho (o-) and para (p.) directing.
- Most of the polyhalogen compounds like freon, DDT, BHC have main industrial applications but they do not decompose easily therefore they are harmful for environment also.
- In chlorai hydrate yet there are two —OH group on one carbon only yet it is stable due to intramolecular hydrogen bonding.
→ Main chemical reactions of alkyl halides are as follows:
→ Main chemical properties of chloroform are as follow:
→ Main chemical properties of halobenzene can be explained by taking example of chioro benzene.
