Halogenoalkanes (4) Hydrolysis reactions

 #1. What happens in the hydrolysis of halogenoalkanes?

Hydrolysis means splitting a molecule using water (H₂O)

Hydrolysis of haloalkanes is faster with hydroxide ions (:OH^–) than with water itself. 

Hydroxide ions are more effective nucleophiles than water molecules.

The ion is more effective because it is smaller than a water molecule and more labile.

The ion is a nucleophile because of the lone pair of electrons.

The reagent used is aqueous alkali e.g. potassium hydroxide solution KOH(aq)

The reaction is a substitution reaction

RX      +       H₂O       =         ROH      +    HX

R—   represents a generic alkyl group  

X—  represents a halogen group

ROH is a corresponding alcohol  

HX is the generic hydrogen halide

The reaction can also be written:

RX      +      :OH^–     =         ROH      +    X^—

You ought to be able to write any example reaction of the haloalkanes using this kind of structural formula template e.g.

CH₃CH₂CH₂Br        +       :OH^–       =         ?

Or this skeletal formula template:

+    :OH^–    =     ?

Try using different alkyl groups etc…..and different halogen substituents

Then ask yourself:
how would I form pentan-1-ol (or other alcohols) by this method?

In the next haloalkane post I’ll discuss the mechanism of simple nucleophilic substitutions in haloalkanes.