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Investigating the rate of hydrolysis of organic halogen
compounds
Background
Organic halogen compounds react with water to produce an alcohol, halide ions
and hydrogen ions. This is an example of a hydrolysis reaction.
For example – 2- bromo 2-methylpropane
(CH3)3CBr(l) + H2O (l) (CH3)3COH aq) + H+(aq) + Br¯ (aq)
The rate of this reaction can be followed by measuring the amount of hydrogen
ions or bromide ions produced in a given time. This can be carried out by
sampling the reaction mixture and carrying out an appropriate titration.
Practical Techniques
You will need to find out how to make accurate solutions and volumetric analysis
(titration).
Where to start
One way of measuring the rate is to time how long it takes to produce a certain
amount of hydrogen ions.
This can be done by stopping the reaction and titrating the remaining solution
with sodium hydroxide. The hydroxide ions will react with the hydrogen ions that
have been produced.
H+(aq) + OH¯ (aq) H2O (l)
From the amount of hydroxide added the amount of hydrogen ions produced can
be calculated. The extent of the reaction can therefore be determined.
Another method might be to add silver ions to the compound dissolved in ethanol
and time how long it takes for the silver bromide precipitate to form. This could be
by marking a cross on a piece of paper and timing how long it takes to obscure
the cross.
