To compare the rate of displacement of the halide ion varies with respect to the C – X bond. C is the carbon atom and X being the halogen. This is a nucleophilic substitution reaction. Background Knowledge: Halogenoalkanes are alkanes that have one of the H atom replaced with a halogen atom. They are classified according to the number of carbon atoms bonded to the carbon atom which has the halogen atom bonded to. They are primary, secondary and tertiary.
A nucleophile is an electron donor; it has one or more lone pairs of electrons which it donates to the carbon atom which has a slightly positive charge due to the difference in electronegativity between the carbon and the halogen atom resulting in the C atom susceptible to attack by an electron rich species (a nucleophile). This results in the C – X bond breaking and a new bond forming between the carbon and the nucleophile. Hence it is a substitution reaction as the halogen is substituted with a new species.
Halogenoalkanes undergo three main nucleophilic substitution reactions. They react with OH-, NH3 and CN- ions. The hydrolysis of the halogenoalkanes which involves the OH- will be used in this experiment. The rate of the reaction depends on the strength of the C – X bond. Stronger bonds need more energy to be broken; therefore they have a higher bond enthalpy value. From the three main types I have chosen the OH- reaction because. CN- is a very toxic substance which is very dangerous to be used in a laboratory.
The reaction with NH3 will produce a wide range of results because it will constantly substitute the chemicals ending up in a big range of amines. The same reaction can be carried out with water, but the rate is very slow with water, therefore it will not be used. The chemicals are kept away from any source of fire. All handled in a safe manner. Skin and eye protection has to be worn i. e. lab coats, gloves and goggles. All the glassware should be handled safely and any breakages should be notified.