REACTION RATES OF HALOGENOALKANES

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REACTION RATES OF HALOGENOALKANES

Introduction

A halogenoalkanes are compounds consisting of Carbon, Hydrogen and halogen atoms such as Fluorine, Chorine, Bromine, Iodine. The general formula of halogenoalkanes is;

CnH2n+1X.

Because of the difference in electronegativity between the carbon atom and the halogens; a Polar Covalent Bond is created.

C?+-X?-

The electron-deficient carbon atom of the polar C?+-X?- bond attracts nucleophiles, permitting a nucleophilic reaction to take place. In this reaction the halogen atom is replaced by the nucleophile.

A nucleophile is an electron-rich species which attacks the electro-deficient carbon atom by donating an electron pair. This process is called nucleophilic substitution.

Bellow is an example of the mechanism for the nucleophilic substitution of bromine in bromobutane by OH¯

(The curly arrows show the direction of movement of electron pair)

Halogenoalkanes are classified into; primary, secondary and tertiary, in respect to their structures.

Primary halogenoalkanes have the halogen atom is covalently bonded to a carbon atom, which has two hydrogen bonded to it.

Secondary halogenoalkanes have the halogen atom is covalently bonded to a carbon atom, which has one hydrogen atom bonded to it and