what is an ester ?

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In chemistry, esters are organic compounds in which an organic group (symbolized by R' in this article) replaces a hydrogen atom (or more than one) in an oxygen acid. An oxygen acid is an acid whose molecule has an -OH group from which the hydrogen (H) can dissociate as an H+ ion.

The most common esters are the carboxylate esters, where the acid in question is a carboxylic acid. For example, if the acid is acetic acid, the ester is called an acetate. Esters may also be formed with inorganic acids; for example, dimethyl sulfate is an ester, and sometimes called "sulfuric acid, dimethyl ester".

Esters are named similarly to salts; although they don't really have cations and anions, the terminology follows the same pattern: a more electropositive part followed by a more electronegative part.

An ester can be thought of as a product of a condensation reaction of an acid (usually an organic acid) and an alcohol (or phenol compound), although there are other ways to form esters. Condensation is a type of chemical reaction in which two molecules are joined together and eliminate a small molecule, in this case two-OH groups are joined eliminating a water molecule. A condensation reaction to form an ester is called esterification. Esterification can be catalysed by the presence of H+ ions. Sulfuric acid is often used as a catalyst for this reaction. The name ester is derived from the German Essig-√Ąther, an old name for acetic acid ethyl ester (ethyl acetate).
Source(s): http://en.wikipedia.org/wiki/Ester
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Esters are nothing but sweet-smelling organic compounds formed by the reaction between an alcohol and a carboxylic acid in presence of sulphuric acid.

Alcohol + Carboxillic Acid --> Ester + Water

C2H5OH + CH3COOH ---> CH3COOC2H5 + H2O

Ethanol + Ethanoic Acid --> Ethylethanoate + water

The function of sulphuric acid is to absorb the water produced and set the reaction in the forward direction.
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An ester is produced when you mix an organic acid and alcohol.Since there are many acids and many alcohos you cam make many esters. Esters are the flavorings used in foods such as apple(methyl butylate) ,ethyl formate (rum) wintergreen(methyl salicylate), pineapple(ethyl butylate),banana (isopently acetate)orange (octyl acetate) .Water is also produced.
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