Aromaticity is a feature of certain planar, fully conjugated ring systems, where the 'whole is more than the sum of the parts' in that the ring is more stable than might be expected by considering the stability of the parts it is made from. Perhaps the prime example of this phenomenon is benzene, a six-membered ring system which has quite a different stability and geometry, and hence chemistry, than expected for cyclohexa-1,3,5-triene, the name for the 'sum of the parts'. As a consequence of this I prefer the symbol: in preference to the symbol: to indicate the benzene ring, though both are acceptable.

I. Monosubstituted Benzene Derivatives

• 1a. For those substituent groups which are named only with prefixes, often the prefix is attached to the parent name in the way we have become used to.

  Examples are:

  ethylbenzene

  t-butylbenzene

  chlorobenzene

  bromobenzene

  nitrobenzene

  ethoxybenzene

• 1.b. Exceptions to this rule are found in that a few derivatives have common names which have been accepted into the IUPAC system. These will have to be learned!

  Examples:

  toluene

  cymene

  anisole

• 2. If the benzene ring is on a carbon chain which is used to form the root name, then the benzene ring uses the prefix: phenyl.

  Examples:

  3-phenyldecane

  5-phenylpentanoic acid

• 3. Most other monosubstituted benzenes have common names which have been accepted into the IUPAC system. And you've guessed it: they must be learned!

  Examples:

  styrene

  aniline

  Simple amides derived from aniline can be named as 'anilides': butanilide

  phenol

  Esters of phenol use the name 'phenyl':
  phenyl ethanoate
  Ethers of phenol can use the prefix 'phenoxy' if necessary:
  3-phenoxyheptane

  acetophenone

  benzophenone

  Other ketones with a benzene ring in them can use the prefix 'phenyl' for the ring: 1-phenylhexan-1-one

  benzaldehyde

  benzamide

  benzoic acid

  Esters of benzoic acid are termed 'benzoates': ethyl benzoate

  phenyl benzoate

Next page : Disubstituted Benzenes

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