Chapter 12 Notes | Chemistry 2nd Year
“Aldehydes And Ketones”
- Aldehydes and ketones contain the carbonyl group, C = O as the functional group.
- Both aldehydes and ketones can be prepared by the oxidation of primary and secondary alcohols respectively.
- Both aldehydes and ketones undergo nucleophilic addition reaction. In these reactions, the negative art of the reagent combines with the electrophilic carbon of the carbonyl group whereas the positive part goes to the oxygen atom they are base catalyzed addition reactions.
- Two molecules of the same carbonyl compound condense to form an aldol. Aldehydes and ketones containing α-hydrogen atoms undergo this reaction in the presence of dilute sodium hydroxide.
- Aldehydes that have no α-hydrogen atom undergo Cannizzaro’s reaction in the presence of concentrated sodium hydroxide.
- Acetaldehyde and only methyl ketones react with halogens in the presence of sodium hydroxide to give haloform. It provides a useful method for converting a methyl ketone to a carboxyl acid containing one carbon atoms less than parent methyl ketone. Iodoform test is used for distinguished methyl ketones from other ketones.
- Aldehydes and ketones react with ammonia derivatives, G- NH2 to form condensation products containing the group C=N-G and wither, the reaction in acid catalyzed.
- Aldehydes and ketones are reduces alcohols with sodium borohydride, aldehydes and ketones are also reduced to alcohols with molecular hydrogen in the presence of catalyst like Pd, Pt, or Ni.
- Aldehydes are oxidized to carboxylic acid K2Cr2O7 or KmnO4 in H2SO4 may be used the oxidizing agent. Ketone resist oxidation.
- Aldehydes from silver mirror with Tollen’s reagent. Ketones do not gove this test.
- Aldehydes give a brick red precipitate with Fehling’s solution on boiling.