Esterification: the synthesis of isoamyl acetate Objective To develop organic laboratory techniques, to synthesize isoamyl acetate (isopentyl acetate), familiarize ourselves with the reactions of carbonyl compounds, and to gain experience using Fourier Transform Infrared (FTIR) Spectroscopy to characterize the product of a reaction. Background The reaction of an alcohol with a carboxylic acid is a straightforward way to synthesize esters. Often these esters have an interesting aroma. Flavors in wines can be created in this way. Wines are rich in a variety of alcohols and acids. When the various acids and alcohols combine, they can form esters, which can add flavors to the wine. Two issues arise when one attempts to do these reactions in the laboratory. First, the reactions are equilibrium reactions. Second, esterification reactions are not particularly fast. O. + H2O eq. 1 ОН Но To encourage product formation the reaction must be driven to completion. An excess of one reagent is added to drive the consumption of the other reagent. Typically, the reagent that is added in excess is the less expensive reagent or the reagent that is more easily separated from the product. In this case, acetic acid is more easily removed from the oily product since acetic acid has a higher solubility in water. The reaction can also be driven to completion by the removal of one of the products, typically through distillation. The second problem, the low reaction rate, is solved by adding a catalyst. The catalyst is an acid. Since many protic acids can catalyze the reaction, the mechanism by which the catalyst acts is referred to as general-acid catalysis. Adding a proton to the reaction increases the rate of the reaction by making two crucial steps faster. First, the formation of the tetrahedral intermediate is encouraged because the carbonyl carbon of the acetic acid becomes more susceptible to nucleophilic attack. Second, the catalyst aids in the proton transfer steps that generate the leaving group. Н+ н, Н. H. H. -C. Но .C FR %3D C-R Но R'-O R'-O R'-O ОН 0-H R'-OH R'-OH H. H.

Esterification: the synthesis of isoamyl acetate Objective To develop organic laboratory techniques, to synthesize isoamyl acetate (isopentyl acetate), familiarize ourselves with the reactions of carbonyl compounds, and to gain experience using Fourier Transform Infrared (FTIR) Spectroscopy to characterize the product of a reaction. Background The reaction of an alcohol with a carboxylic acid is a straightforward way to synthesize esters. Often these esters have an interesting aroma. Flavors in wines can be created in this way. Wines are rich in a variety of alcohols and acids. When the various acids and alcohols combine, they can form esters, which can add flavors to the wine. Two issues arise when one attempts to do these reactions in the laboratory. First, the reactions are equilibrium reactions. Second, esterification reactions are not particularly fast. O. + H2O eq. 1 ОН Но To encourage product formation the reaction must be driven to completion. An excess of one reagent is added to drive the consumption of the other reagent. Typically, the reagent that is added in excess is the less expensive reagent or the reagent that is more easily separated from the product. In this case, acetic acid is more easily removed from the oily product since acetic acid has a higher solubility in water. The reaction can also be driven to completion by the removal of one of the products, typically through distillation. The second problem, the low reaction rate, is solved by adding a catalyst. The catalyst is an acid. Since many protic acids can catalyze the reaction, the mechanism by which the catalyst acts is referred to as general-acid catalysis. Adding a proton to the reaction increases the rate of the reaction by making two crucial steps faster. First, the formation of the tetrahedral intermediate is encouraged because the carbonyl carbon of the acetic acid becomes more susceptible to nucleophilic attack. Second, the catalyst aids in the proton transfer steps that generate the leaving group. Н+ н, Н. H. H. -C. Но .C FR %3D C-R Но R'-O R'-O R'-O ОН 0-H R'-OH R'-OH H. H.

Organic Chemistry

9th Edition

ISBN:9781305080485

Author:John E. McMurry

Publisher:John E. McMurry

Chapter17: Alcohols And Phenols

Section17.SE: Something Extra

Problem 71AP: A problem often encountered in the oxidation of primary alcohols to acids is that esters are...

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