Naming of Alkyl Halides (Halo Alkanes) & Aryl Halides (Halo Arenes)

INTRODUCTION

Alkyl halides or halo alkanes are compounds in which a halogen is bonded to an alkyl group. They have the general formula RX (where R is alkyl group C_nH_2n+1) X is halogen atom.

$\underset{alkane}{\mathrm{RH}}\stackrel{-H,+X}{\to }\underset{alkylhalide}{\mathrm{RX}}$

Alkyl halides are classified as primary, secondary and tertiary alky halides depending on whether the halogen atom is attached to a primary, secondary or tertiary carbon atom respectively.

For example

Aromatic halogen compounds or halo arenes are the halogen compounds which contain atleast one aromatic ring. Halogen derivatives of aromatic compounds are of two types.

1. Aryl halides

In this type of compounds, the halogen atom is directly linked to the carbon of benzene nucleus e.g.

2. Aralkyl halides

In this type of compounds halogen is linked to the carbon atom of the side chain.

NOMENCLATURE OF ALKYL & ARYL HALIDES

In the common system, aliphatic halogen derivatives are named as alkyl halides. The words

n$-$, sec$-$, tert$-$, iso$-$, neo$-$ & amyl are usually used in writing the common names. In IUPAC nomenclature they are named as halo alkanes.

Example:

The dihalogen derivatives having same type of halogen atoms on the same carbon are known as geminal dihalides and are assigned common name alkylidene halides.

The dihalogen derivatives having 2 similar halogen atoms on adjacent carbon atoms are known as vicinal dihalides & are assigned common name alkylene halides.

Tri halo methanes are called haloforms in trivial system.

Example:

Haloarenes are named by prefixing the halogen and its position.

Illustration 1. Write structural formulae of 3 Bromo hexane.

Solution: