Ester

In organic chemistry and biochemistry esters are a functional group consisting of an organic radical united with the residue of any oxygen acid, organic or inorganic. The most common esters found in nature are fats, which are esters of glycerine and fatty acids, oleic, etc.

mainly resulting from the condensation of a carboxylic acid and an alcohol. The process is called esterification[?]:

Naming of esters:

              O
              ||
              C - CH3
             /
  CH3 - CH2-O

    ethyl      acetate/ethanoate 
  (comes from    (comes from
  the alcohol)      the acid)

Physical properties:

Esters can participate in hydrogen bonds as hydrogen bond acceptors, but cannot act as hydrogen bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonds leads them to be more water soluble than their parent hydrocarbons. But the limitations on their hydrogen bonding also make them more hydrophobic than either their parent alcohols or parent acids. Their lack of hydrogen-bond donating ability means that they can't form hydrogen bonds between ester molecules, which makes them generally more volatile than an acid or ester of similar molecular weight.

Many esters have distinctive odors, which leads to their widespread use as artificial flavorings and fragrances. For example:

methyl butanoate smells of pineapple

methyl salicylate (oil of wintergreen) smells of the ointments called Germolene™ and Ralgex™ in the UK

ethyl methanoate smells of raspberry

pentyl ethanoate smells of banana

pentyl pentanoate smells of apple

pentyl butanoate smells of pear or apricot

octyl ethanoate smells of orange

Esters also participate in ester hydrolysis - the breakdown of an ester by water. Esters may also be decomposed by strong acids or bases. As the result they are decomposed into an alcohol and a carboxylic acid, or a salt of carboxylic acid

See also: transesterification