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Nomenclature of Esters

  • Page ID
    5922
  • Esters are known for their distinctive odors and are commonly used for food aroma and fragrances. The general formula of an ester is RCOOR'.

    Introduction

    Esters are formed through reactions between an acid and an alcohol with the elimination of water. An example of this is the reaction of acetic acid with an alcohol, which yields an acetic ester and water.

    The part enclosed by the red circle represents the ethyl group from the alcohol and the part enclosed by the green rectangle represents the acetate group from the acid.

    Esters can be named using a few steps

    Esters are named as if the alkyl chain from the alcohol is a substituent. No number is assigned to this alkyl chain. This is followed by the name of the parent chain from the carboxylic acid part of the ester with an –e remove and replaced with the ending –oate.

    Example

    Ester2.jpg

    Esters are formed through reactions between an acid and an alcohol with the elimination of water. An example

    1. First, identify the oxygen that is part of the continuous chain and bonded to carbon on both sides. (On one side of this oxygen there will be a carbonyl present but on the other side there won't be.)

    2. Second, begin numbering the carbon chains on either side of the oxygen identified in step 1.

    3. Next, use this format: [alkyl on side further from the carbonyl] (space) [alkane on the side with the carbonyl] - (In this case: [methyl] [methane])

    4. Finally, change the ending of the alkane on the same side as the carbonyl from -e to -oate. (In this case: methyl methanoate)

    When an ester group is attached to a ring, the ester is named as a substituent on the ring.

    Benzenecarboxylic acid (Benzoic acid)

    Other substituents that exist on either side of the ester are named in the same way as they are on regular alkane chains. The only thing you must make sure of is placing the substituent name on the part of the name that corresponds to the side of the ester that it is on.

    1-chloromethyl ethanoate

    methyl 2-chloroethanoate

    CH3COOCH2CH3

    methyl propanoate

    CH3COOCH2CH2CH2CH2CH2CH2CH2CH3

    octyl ethanoate

    References

    1. Leigh, G. J., H. Favre, and Val Metanomski. Principles of Chemical Nomenclature A Guide to Iupac Recommendations (IUPAC Chemical Data Series). Malden: Blackwell Science, 1998.
    2. McNaught, A. D., and A. Wilkinson. Compendium of Chemical Terminology. 2nd ed. Blackwell Science, 1997.
    3. Vollhardt, K. Peter C., and Neil E. Schore. Organic Chemistry Structure and Function. New York: W. H. Freeman, 2007.

    Problems

    Name the following:

    Answer: propyl ethanoate

    Answer: 3-bromopentyl 2-chlorobutanoate

    Answer: ethyl hexanoate

    Answer: ethyl 3-bromopentanoate

    Answer: 4-nitrobenzenecarboxylic acid or

    4-nitrobenzoic acid

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