The reactivity of alcohols can be understood by examining the electron distribution within the C-OH group. It is similar to that of the haloalkanes but the result is very different. Why?
Alkyl Halide
The halogen atom is very electronegative and heavily polarizes the C-X bond.
Furthermore, the halide is a very good leaving group and can be expelled by a good nucleophile.
THIS DOES NOT HAPPEN TO ALCOHOLS.
Alcohol
The electronegative oxygen polarizes the C-O bond in a similar way the halogen does.
But, on the contrary to the halogen, the hydroxide is an extremely bad leaving group.
Hence, alcohols don't directly react with nucleophiles.
In addition, alcohols display acidity, a property not shown by the corresponding halides.
The weak acidity of the OH group makes alcohols give reactions not possible with the alkyl halides.
Alkyl Halide
Alcohol
