Fischer Esterification

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Fischer Esterification of (1,3-Dimethylbutyl) Acetate from 4-Methyl-2-Pentanol

Alison Evans
Anne Richards
TA: Dylan Kahl
Tuesday
11:30am - 2:20pm
81807

Abstract:
An ester was synthesized during an organic reaction and identified by IR spectroscopy and boiling point. Acetic acid was added to 4-methyl-2-pentanol, which was catalyzed by sulfuric acid. This produced the desired ester and water. After the ester was isolated a percent yield of 55.1% was calculated from the 0.872 g of ester recovered. This quantitative error was most likely due to product getting stuck in the apparatus. The boiling point of the ester was 143° C, only one degree off from the theoretical boiling point of the ester 1,3-dimethylbutyl, 144 ° C. The values of the major peaks on the IR spectrum also corresponded to the theoretical values of the ester 1,3-dimethylbutyl. Therefore, it was concluded that this was the ester formed and the experiment was a success, because even though there was error, this was only in the amount of the ester, not in its identity. Introduction

Fischer Esterification is the simplest means of synthesizing an ester and requires the reaction of a carboxylic acid and an alcohol. The general reaction of Fischer esterification is, CH3CO2H + ROH ↔ CH3CO2R + H2O (reaction 1)

An alcohol (ROH in reaction 1) is a functional group containing a hydrogen, oxygen bond. Carboxylic acids (CH3CO2H in reaction 1) are characterized by a carbon, oxygen double bond, with one alcohol group and an alkyl or aromatic side chain. Esters (CH3CO2R in reaction 1) are identified by a carbon, oxygen double bond and an oxygen alkyl or aromatic group. Carboxylic esters often have pleasant odors and are used in foods and beverages to create flavors mimicking fruit. Depending on the ester synthesized smells such as banana, pineapple, or orange can be obtained. Reaction one is a double displacement reaction. The carboxylic acid donates its hydrogen atom to the to the alcohol group, which accounts for water as a product. The ester is formed by the carboxylic acid gaining the alkyl side chain of the alcohol. A catalysis is added to the reaction in order to accelerate the process. The catalysis used in reaction 1 is sulfuric acid, H2SO4. The reaction also occurs in reflux, meaning it is boiled at a high temperature, also accelerating the process. The reaction of a carboxylic acid and an alcohol, like in reaction 1, is in equilibrium. A reaction in equilibrium means the net change of the products and reactants is zero. The equilibrium is dynamic because the reaction is still occurring but the amount of reactants and products is no longer changing. In order to create more ester, the reaction must be shifted to the right, the product’s side. The reaction can be shifted to the right most easily by adding more reactants, specifically an excess of the carboxylic acid. The reaction will adjust to the right because of added reactant by creating more products, i.e. more ester. Considering that the reaction has an excess of the carboxylic acid, the alcohol will be the limiting reactant. The amount of ester yielded will depend upon the amount of alcohol in the reaction. The alcohol being used in this specific Fischer esterification is 4-methyl-2-pentanol. The specific reaction is, CH3CO2H + CH3CH(CH3)CH2CH(OH)CH3↔CH3CO2(CH2)3CH + H2O (reaction 2) Sulfuric acid is used as a catalysis in reaction 2, similar to reaction 1. The reaction occurs by the carboxylic acid donating a proton in the form of hydrogen to the alcohol. The oxygen of the carboxylic acid is now able to bond with the alkyl group of the alcohol creating the ester. The reaction will occur in reflux, meaning it will be boiled at a high temperature for a significant amount of time. Reflux gives the ability to isolate the ester from the other components of the reaction and therefore purifies the ester. The water is removed from the ester with the aid of sodium bicarbonate. The...
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