The haloalkanes represent an extremely versatile group of molecules which would be well worth taking with you onto your desert island...should you ever find yourself marooned. The polar bond introduced with the appearance of the halogen atom gives the carbon atom a delta-positive charge...and so invites the attention of a nucleophile, which is quick to effect a substitution reaction so charactersitic of saturated substrates.
The most polar may well be the C-Cl bond, but the most reactive is the C-I, since the latter is the longest and therefore the weakest. This fact is easily proven by the rate of the reaction with hydroxide ion, releasing the halide ion to react with aqueous silver (I) ion and give a ppt of silver iodide.
Remember that the haloalkanes may be prepared by reaction of alkenes with halogen or hydrogen halide [electrophilic addition] or from alkanes via a free radical substitution type of reaction.
Posted by dcox at October 12, 2009 08:32 AM