Carbonyl Compounds

In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound.

Course Contents

  • Aldehydes (exemplified by ethanal)
  • (i) oxidation to carboxylic acid
  • (ii) nucleophilic addition with hydrogen cyanide
  • (iii) characteristic tests for aldehydes
  • Ketones (exemplified by propanone and phenylethanone)
  • (i) nucleophilic addition with hydrogen cyanide
  • (ii) characteristic tests for ketones

Learning Outcomes

Candidates should be able to:

  • (a) describe the formation of aldehydes and ketones from, and their reduction to, primary and secondary alcohols respectively
  • (b) describe the mechanism of the nucleophilic addition reactions of hydrogen cyanide with aldehydes and ketones
  • (c) explain the differences in reactivity between carbonyl compounds and alkenes towards nucleophilic reagents, such as lithium aluminium hydride and hydrogen cyanide
  • (d) describe the use of 2,4-dinitrophenylhydrazine (2,4-DNPH) to detect the presence of carbonyl compounds
  • (e) deduce the nature (aldehyde or ketone) of an unknown carbonyl compound from the results of simple tests (i.e. Fehling’s and Tollens’ reagents; ease of oxidation)
  • (f) deduce the presence of a CH3CO– group in a carbonyl compound from its reaction with alkaline aqueous iodine to form tri-iodomethane