Essay On Esters

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Introduction Methyl butyrate or methyl ester of butyric acid is an ester with a fruity odor of pineapple, apple and strawberry. Present in small amounts in several plant products, especially pineapple flavor is produced by distillation from essential oils of vegetable origin. This ester is also manufactured on a small scale for use in perfumes or food flavors. Esters, in general, can be defined as the reaction products of carboxylic acids and organic alcohols. Chemically, an ester is the condensation product that results when a carboxylic acid is reacted with an alcohol1. Esterification of carboxylic acids with alcohols represents a well-known category of liquid-phase reactions of considerable industrial interest due to enormous practical importance of organic ester products. Esters are important fine chemicals used widely in the manufacturing of flavors, pharmaceuticals, plasticizers, solvents of paints, adhesives, pesticides, polymerization monomers and in the preparation of biodiesel from lower quality feedstock. Derivatives of some esters are useful as chemical intermediates and monomers for resins and high molecular weight polymers. They are also used as emulsifiers in the food and cosmetic industries2, 3. Many routes are available for organic esters synthesis. The traditional route for preparing esters is via reaction of the carboxylic acid with an alcohol using homogeneous catalysts such as sulfuric acid or para-toluene-sulfonic acid4,5,6. Esterification can take place without adding catalysts due to weak acidity of carboxylic acids themselves. However, the reaction is extremely slow and requires long time to reach equilibrium at typical reaction conditions7. A common method of operating equilibrium limited reactions is to... ... middle of paper ... ...terification with methanol increases with an increase in temperature over the range of study (323-343 K); passes through maximum with increasing alcohol to acid ratio (1-4); increases with the increase in catalyst loading(0-8.5 % w/w). Conversion was optimum for the stirrer speed of 300 rpm indicating the absence of film diffusion. The conversion of butyric acid was dropped in the presence of added water due to inhibiting effect of water. The maximum conversion of 94.5 % was observed at optimum reaction conditions. Thus, the ion exchange catalyst was found to be very effective for the methyl butyrate synthesis. The Langmuir-Hinshelwood-Hougen-Watson Dual Site (considering reactants and products adsorbed on catalyst surface) heterogeneous model could be successfully applied for representing esterification kinetics for the reaction between butyric acid and methanol.
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