These compounds contain the -OH functional group. There is a school of thought that includes water in this category, since this too contains the -OH group. I leave it to you to decide whether to subscribe to this ideal, but you can guess my conclusion!
They are often prepared by a nucleophilic substitution reaction on a haloalkane. The reagent for this is often aqueous sodium hydroxide, and the reaction mixture is heated under reflux.
Alcohols will burn, but this destructive oxidation is of no use...unless you happen to want to enjoy the energy stored in the bonds to cook on.
Oxidation is best described as the addition of oxygen or the removal of hydrogen [as water]. These statements describe exactly what happens to the molecules.
Oxidation that preserves the carbon skeleton is effected using potassium dichromate (VI) in dilute sulphuric acid. This is a delightful orange colour, and if it does its job it will end up green.
Alcohols are classified as primary, secondary or tertiary. This is determined by looking at the alcoholic carbon atom and counting how many other carbon atoms this is bonded to...and making the connection! That's fine except for methanol..but this is always classified as primary.
Oxidation of primary alcohols yields firstly the aldehyde and then subsequently the carboxylic acid. To stop at the aldehyde, add the oxidant to the warm alcohol and distill out the aldehyde as quickly as it is formed. The acid is obtained by arranging to heat the mixture under reflux.
Secondary alcohols will give ketones. Tertiary alcohols are resistant since the alcoholic carbon atom does not carry the hydrogen atom necessary for the first step of the reaction.
Posted by dcox at May 15, 2010 08:30 PM