Word of the Day – Weekend Edition



Word of the Day


Clever Clue of the Month

The Cruciverbalist


Daily Email

ESTER (ESS-tuhr)

Any one of a group of organic compounds that are formed by the reaction between an alcohol and an acid
Common clues: Organic compound; Perfume ingredient; Aromatic compound; Banana oil, for one; Chemical compound; Fragrant compound; Any acetate chemically
Crossword puzzle frequency: 4 times a year
Frequency in English language: 39571 / 86800

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.

Esters 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 bonding makes them more water-soluble than their parent hydrocarbons. However, 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 ester molecules cannot hydrogen-bond to each other, which makes esters generally more volatile than a carboxylic acid of similar molecular weight. This property makes them very useful in organic analytical chemistry: unknown organic acids with low volatility can often be esterified into a volatile ester, which can then be analysed using gas chromatography, gas liquid chromatography, or mass spectrometry. Many esters have distinctive odors, which has led to their use as artificial flavorings and fragrances. For example:

allyl hexanoate pineapple

benzyl acetate pear, strawberry, jasmine

bornyl acetate pine tree flavor

butyl butyrate pineapple

ethyl acetate peach, pineapple, raspberry

ethyl butyrate banana, pineapple, strawberry

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ester".