Ester

Nomenclature

An ester is named according to the two parts that make it up: the part from the alcohol and the part from the acid (in that order), for example ethyl sulfuric acid ester.

Since most esters are derived from carboxylic acids, a specific nomenclature is used for them. For esters derived from the simplest carboxylic acids, the traditional name for the acid constituent is generally retained, e.g., formate, acetate, propionate, butyrate.^[1] For esters from more complex carboxylic acids, the systematic name for the acid is used, followed by the suffix -oate. For example, methyl formate is the ester of methanol and methanoic acid (formic acid): the simplest ester. It could also be called methyl methanoate.^[2]

Esters of benzoates such as methyl benzoate, and phthalates, with substitution allowed in the name.

Physical properties

Esters participate in mass spectrometry. Many esters have distinctive odors, which has led to their use as artificial flavorings and fragrances. For example:

Ester synthesis

"Esterification" (condensation of an alcohol and an acid) is not the only way to synthesize an ester. Esters can be prepared in the laboratory in a number of other ways:

• by transesterifications between other esters
• by Claisen condensation of esters carrying acidic α-protons
• by Favorskii rearrangement of α-haloketones in presence of base
• by nucleophilic displacement of alkyl halides with carboxylic acid salts
• by Baeyer-Villiger oxidation of ketones with peroxides
• by Pinner reaction of nitriles with an alcohol

Ester reactions

  Esters react in a number of ways:

• Esters may undergo salt.
• Esters also react if heated with primary or secondary amides.
• Phenyl esters react to hydroxyarylketones in the Fries rearrangement.
• Di-esters such as malonic ester synthesis after deprotonation.
• Specific esters are functionalized with an α-hydroxyl group in the Chan rearrangement.
• Esters are converted to hydroxamic acids in the Lossen rearrangement.
• Esters with β-hydrogen atoms can be converted to alkenes in ester pyrolysis.

References

1. ^ IUPAC parent groups using traditional names
2. ^ IUPAC naming of esters