Basic Organic Nomenclature

An Introduction

Dave Woodcock,
Associate Professor Emeritus UBC (Okanagan)
©1996,2000, 2008

6. Aromatic Compouds

I Monosubstituted Benzenes

Index



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

Self Assignment Questions
Review Alkanoates, Esters

Next page : Disubstituted Benzenes

Index


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