IB DP Chemistry: SL复习笔记10.1.7 Organic Families - Carbonyls


  • Carbonyl is the collective name for compounds containing the functional group C=O
  • The general formula of a carbonyl is CnH2nO
  • The two sub-families of carbonyls are aldehyde and ketone (known in some countries as alkanals and alkanones)


  • If the carbonyl group is on the end of a chain then it is an aldehyde and has the functional group formula, RCHO
    • the H is written before the O so as not to confuse it with an alcohol
  • The nomenclature of carbonyls follows the pattern alkan + al
  • There is no need to use numbers in the name as aldehyde will always be on the number 1 carbon atom


  • Ketones have a minimum of three carbons and have the general functional group formula, RCOR
  • The nomenclature of ketones follows the pattern alkan + one
  • After butanone, the carbonyl group can have positional isomers, so numbering must be used
    • For example pentan-2-one and pentan-3-one

Aldehyde and Ketone Examples Table


  • As they have a very similar functional group arrangement, aldehydes and ketones show similar chemical reactions
  • Differences in their chemistry are due to the reactions that involve the H on the aldehyde or the nature of the R group
  • The difference in electronegativity between oxygen and carbon means the C=O is polar, leading to dipole-dipole attractions between the molecules which results in:
    • higher than expected boiling points for small molecules
    • solubility in water for the lower members of the families
  • Aldehydes and ketones with the same number of carbons are functional group isomers