Introduction of Haloalkens and Haloarenes – Definition, Classification, Uses
In the previous unit we learnt about the chemistry of hydrocarbons. In this unit us learn about organic compounds containing halogens. When one or more hydrogen atoms of aliphatic or aromatic hydrocarbons are replaced by the corresponding number of halogens like fluorine, chlorine, bromine or iodine, the resultant compounds are called either haloalkanes or halo arenes. They serve as starting materials for many organic synthesis.
Halogen substituted organic compounds are widely spread in nature and find application in our day to day life as well as in industry. Certain compounds like chloramphenicol produced by soil microbes are used in the treatment of typhoid; chloroquine is used in the treatment of malaria, halothane is used as an anesthetic, and halogenated solvents like trichloroethylene are used for cleaning electronic equipments.
Haloalkanes are hydrocarbons containing aliphatic alkane with one or more hydrogen atoms replaced by halogens. Haloarenes are hydrocarbons containing aromatic alkane with one or more hydrogen atoms replaced by halogens.
Classification of Haloalkanes
The haloalkanes, also known as alkyl halides, are a group of chemical compounds comprised of an alkane with one or more hydrogens replaced by a halogen atom (fluorine, chlorine, bromine, or iodine). The classification is determined by the number of carbons bonded to the carbon bearing the halide.
Name of Haloalkanes and Haloarenes
IUPAC name – The IUPAC (International Union of Pure and Applied Chemistry) naming system is the standard naming system that chemists generally use.
Reaction of Haloalkanes and Haloarenes
Haloarenes are more stable than the haloalkane that’s why haloarenes are less reactive than the haloalkane. The reasons for being stable are dependent on mainly three factors that are polarity of carbon-halogen bond, hybrid state of the carbon atom in the haloarenes and the presence of resonance.
Halide Functional Group
An acyl halide (also known as an acid halide) is a chemical compound derived from an oxoacid by replacing a hydroxyl group with a halide group. If the acid is a carboxylic acid, the compound contains a – COX functional group, which consists of a carbonyl group singly bonded to a halogen atom.
Functional Group of Haloalkenes
Alkyl halides [haloalkanes] consist of an alkyl group attached to a halogen: F, Cl, Br, I. Chloro, bromo and iodo alkyl halides are often susceptible to elimination and/or nucleophilic substitution reactions. Aldehydes have a hydrogen and an alkyl (or aromatic) group attached to a carbonyl function.
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