Classification And Nomenclature
Classification: Alkyl halides are formed when a hydrogen atom in a hydrocarbon is substituted by a halogen atom. Haloarenes are formed when a hydrogen atom in a benzene group is replaced by a halogen atom. Alkyl halides (haloalkanes) can be classified by the number of halogen atoms in the molecule. Monohaloalkane and chlorobenzene each contains one halogen atom. Dihaloalkanes and Dihaloarenes have two halogen atoms. Tri-haloalkanes and trihaloarenes contain three halogen atoms. Based on the hybridisation of the carbon atom to which the halogen atom is bonded, monohalocompounds are classified as alkyl halides, allylic halides, benzylic halides, vinylic halides and aryl halides. In alkyl, allyl and benzyl halides, the halogen atom is attached to a sp3 hybridised carbon atom. In vinyl and aryl halides, the halogen atom is attached to a sp2 hybridised carbon atom. Alkyl halides (haloalkanes) and benzylic halides can be classified as primary, secondary (or) tertiary. In primary alkyl halides, the halogen atom is attached to a primary carbon atom. Ex: Ethyl chloride is a primary alkyl halide. In secondary alkyl halides, the halogen atom is attached to a secondary carbon atom. Ex: Isopropyl chloride In tertiary alkyl halides, the halogen atom is attached to a tertiary carbon atom. Ex: Tertiary butyl chloride The alkyl halides (or) haloalkanes have the general formula R-X. R represents an alkyl group. In these compounds, the halogen atom is bonded to sp3 hybridised carbon atom. Nomenclature: Haloalkanes can be named as substituted alkanes in IUPAC nomenclature. Select the longest continuous carbon chain. Check whether longest carbon chain is saturated or unsaturated. Identify the location of halogen in the molecule and it should be given least possible number. Ex: Haloarenes can be named as substituted arenes in IUPAC nomenclature. Dihalogenated compounds with the same type of halogen atoms can be classified based on whether the halogen atoms are on the same or adjacent carbons. If the two halogen atoms are bonded to the same carbon atom, then it is called a "geminal dihalide". Geminal dihalides, in the common system are named alkylidene halides. In the IUPAC system, they named as 1, 1 dihaloalkanes. If two halogen atoms of the same type are bonded to adjacent carbon atoms, it is called a "vicinal dihalide". Vicinal dihalides in the common system are also named as alkylene dihalides. In the IUPAC system, they named as 1, 2 dihaloalkanes.

#### Summary

Classification: Alkyl halides are formed when a hydrogen atom in a hydrocarbon is substituted by a halogen atom. Haloarenes are formed when a hydrogen atom in a benzene group is replaced by a halogen atom. Alkyl halides (haloalkanes) can be classified by the number of halogen atoms in the molecule. Monohaloalkane and chlorobenzene each contains one halogen atom. Dihaloalkanes and Dihaloarenes have two halogen atoms. Tri-haloalkanes and trihaloarenes contain three halogen atoms. Based on the hybridisation of the carbon atom to which the halogen atom is bonded, monohalocompounds are classified as alkyl halides, allylic halides, benzylic halides, vinylic halides and aryl halides. In alkyl, allyl and benzyl halides, the halogen atom is attached to a sp3 hybridised carbon atom. In vinyl and aryl halides, the halogen atom is attached to a sp2 hybridised carbon atom. Alkyl halides (haloalkanes) and benzylic halides can be classified as primary, secondary (or) tertiary. In primary alkyl halides, the halogen atom is attached to a primary carbon atom. Ex: Ethyl chloride is a primary alkyl halide. In secondary alkyl halides, the halogen atom is attached to a secondary carbon atom. Ex: Isopropyl chloride In tertiary alkyl halides, the halogen atom is attached to a tertiary carbon atom. Ex: Tertiary butyl chloride The alkyl halides (or) haloalkanes have the general formula R-X. R represents an alkyl group. In these compounds, the halogen atom is bonded to sp3 hybridised carbon atom. Nomenclature: Haloalkanes can be named as substituted alkanes in IUPAC nomenclature. Select the longest continuous carbon chain. Check whether longest carbon chain is saturated or unsaturated. Identify the location of halogen in the molecule and it should be given least possible number. Ex: Haloarenes can be named as substituted arenes in IUPAC nomenclature. Dihalogenated compounds with the same type of halogen atoms can be classified based on whether the halogen atoms are on the same or adjacent carbons. If the two halogen atoms are bonded to the same carbon atom, then it is called a "geminal dihalide". Geminal dihalides, in the common system are named alkylidene halides. In the IUPAC system, they named as 1, 1 dihaloalkanes. If two halogen atoms of the same type are bonded to adjacent carbon atoms, it is called a "vicinal dihalide". Vicinal dihalides in the common system are also named as alkylene dihalides. In the IUPAC system, they named as 1, 2 dihaloalkanes.

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