Alkyl Halides and Aryl Halides

• What are haloalkanes and haloarenes or Alkyl Halides and Aryl Halides?

These are the organic compounds containing halogen atoms as a substituent . Organic compounds containing C-X bonds are of following types:

1. Alkyl halides or haloalkanes (R—X) : The halogen atom is bonded to an alkyl group (R). They form a homologous series represented by C_nH_2n+1X. 

2. Allylic halides:  The halogen atom is bonded to an sp³-hybridised carbon atom next to carbon-carbon double bond (C=C) i.e. to an allylic carbon.

3. Benzylic halides: The halogen atom is bonded to an sp³-hybridised carbon atom next to an aromatic ring.

4. Vinylic halides: The halogen atom is bonded to an sp² -hybridised carbon atom of a carbon-carbon double bond

5. Aryl halides: The halogen atom is bonded to the sp² - hybridised carbon atom of an aromatic ring.

In this chapter we would focus on alkyl halides and aryl halides only under following subtopics:

• Alkyl Halides 

• S_N1 & S_N2 reactions

• Aryl Halides

• Solved Examples on Alkyl & Aryl Halides

The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds, consisting of alkanes, such as methane or ethane, with one or more halogens linked, such as chlorine or fluorine, making them a type of organic halide. They are a subset of the halocarbons, similar to haloalkenes and haloaromatics. They are known under many chemical and commercial names. As flame retardants, fire extinguishants, refrigerants, propellants and solvents they have or had wide use. Some haloalkanes (those containing chlorine or bromine) have been shown to have negative effects on the environment such as ozone depletion. The most widely known family within this group is the chlorofluorocarbons (CFCs).

• Structure and Nomenclature of Alkyl Halides:

Alkyl halides are commonly designated by the formulas R-X, where R is any simple alkyl or substituted alkyl group. For example,

Substituted alkyl halides undergo, of course, the reactions characteristic of their other functional groups nitration of benzyl chloride, oxidation of ethylene bromohydrin, addition to allyl bromide but as halides they react very much like ethyl or isopropyl or-tert-butyl halides. Compounds in which halogen atom is attached directly to an aromatic ring (aryl halides, e.g., bromobenzene) differ so much from the alkyl halides in their preparation and properties that they will be discussed separately.

• Classification of Haloalkanes and Haloarenes:

Alkyl Halides and Aryl Halides are classified as mono, di, or polyhalogen (tri-,tetra-, etc.) compounds depending on the number of halogen atoms in their structures.

For example

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