General methods of preparation of aldehydes and ketones

(a) By oxidation of alcohols: primary alcohols are oxidised to aldehydes, and secondary alcohols to ketones (this reaction itself was covered in Chapter 11); the oxidant used has to be a MILD, carefully controlled one, since a stronger oxidant would carry the aldehyde on further, all the way to the carboxylic acid. By dehydrogenation of alcohols: passing the vapours of a primary or secondary alcohol over hot copper powder gives, respectively, an aldehyde or a ketone (again, see Chapter 11); this dehydrogenation route has real industrial application, since it avoids needing a separate oxidising reagent at all. (b) From hydrocarbons: by OZONOLYSIS, an alkene first reacts with ozone to form an unstable ozonide, which is then decomposed with zinc dust and water to give the corresponding aldehyde(s) and/or ketone(s), depending on how substituted each alkene carbon was (covered fully in Std. XI Chemistry, Ch. 15). By HYDRATION OF ALKYNES, an alkyne reacts with water in the presence of 40% sulfuric acid and 1% m …