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An Ester is, quite literally, a combination of an alcohol and an organic acid. The combination is a chemical change called an Esterification Reaction; a type of a Dehydrolysis Reaction, meaning that water is removed and appears as a product. As the water comes out, the remaining parts fuse to form an ester. A common type of esterification is the Fischer reaction, an acid catalyzed chemical change. In the Fischer reaction, the acid catalyst donates a proton to the doubly bonded oxygen of the organic acid. This causes a pair of electrons to move away from the carbonyl carbon (the one doubly bonded to oxygen), which places a partial positive charge on the carbon. That carbon attracts and bonds to the electron-rich oxygen of the alcohol, while the proton of the -OH group quickly leaves. Then another proton from the acid attaches to the remaining pair of electrons on the original doubly bonded oxygen. This produces a water molecule, a very stable entity which quickly detaches as free water. The reaction is almost done at this point: The remaining proton of the original -OH group from the carboxylic acid leaves and an ester is formed.
The resulting ester (in the case of longer carbon chain alcohols) has a much lower vapor pressure and, consequently, a higher boiling point than both the organic acid and alcohol, from which it is formed. This is due to greater strength London Dispersion forces vs. those of the alcohol and organic acid. The other interesting property of an ester is its fruity smell, which varies greatly depending on the type of organic acid and alcohol reacted. A diagram, taken from an earlier post, shows two different esters and their differing fruity odors.
The Butyl Acetate from the chart, above, is made from acetic acid and butanol, and the three compounds have boiling points of 126.1, 118.1, and 117.7 degrees Celcius, respectively. The lower boiling points of the reactants allow any excess remaining, upon maximum production of product, to be easily separated out by distillation, leaving pure Butyl Acetate in the reaction vessel.
That's all for this post. As always, thank you for reading!
A Publication of http://www.ExcellenceInLearning.biz
An Ester is, quite literally, a combination of an alcohol and an organic acid. The combination is a chemical change called an Esterification Reaction; a type of a Dehydrolysis Reaction, meaning that water is removed and appears as a product. As the water comes out, the remaining parts fuse to form an ester. A common type of esterification is the Fischer reaction, an acid catalyzed chemical change. In the Fischer reaction, the acid catalyst donates a proton to the doubly bonded oxygen of the organic acid. This causes a pair of electrons to move away from the carbonyl carbon (the one doubly bonded to oxygen), which places a partial positive charge on the carbon. That carbon attracts and bonds to the electron-rich oxygen of the alcohol, while the proton of the -OH group quickly leaves. Then another proton from the acid attaches to the remaining pair of electrons on the original doubly bonded oxygen. This produces a water molecule, a very stable entity which quickly detaches as free water. The reaction is almost done at this point: The remaining proton of the original -OH group from the carboxylic acid leaves and an ester is formed.
The resulting ester (in the case of longer carbon chain alcohols) has a much lower vapor pressure and, consequently, a higher boiling point than both the organic acid and alcohol, from which it is formed. This is due to greater strength London Dispersion forces vs. those of the alcohol and organic acid. The other interesting property of an ester is its fruity smell, which varies greatly depending on the type of organic acid and alcohol reacted. A diagram, taken from an earlier post, shows two different esters and their differing fruity odors.
The Butyl Acetate from the chart, above, is made from acetic acid and butanol, and the three compounds have boiling points of 126.1, 118.1, and 117.7 degrees Celcius, respectively. The lower boiling points of the reactants allow any excess remaining, upon maximum production of product, to be easily separated out by distillation, leaving pure Butyl Acetate in the reaction vessel.
That's all for this post. As always, thank you for reading!
A Publication of http://www.ExcellenceInLearning.biz
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