Fisher esterification synthesis of ethyl acetate

I. INTRODUCTION
The esterification reaction is a crucial reaction in organic chemistry, through which many ester compounds with practical value can be generated. As a commonly used organic solvent and an important intermediate in organic synthesis, the synthesis method of ethyl acetate has attracted much attention. As a classic way to synthesize ethyl acetate, the Fisher esterification method has unique reaction mechanism and application advantages.

II. EXPERIMENTAL PRINCIPLE
The Fisher esterification reaction is based on a reversible reaction between alcohol and carboxylic acid under the action of acid catalysts. Taking ethyl acetate from ethanol and acetic acid as an example, the reaction equation is: $CH_ {3} COOH + C_ {2} H_ {5} OH\ underset {\ Delta} {\ overset {H ^{+}}{\ rightleft harpoons}} CH_ {3} COOC_ {2} H_ {5} + H_ {2} O $. In this reaction, acid catalysts (such as concentrated sulfuric acid) can enhance the electrophilicity of carboxylic acids, promote the hydroxyl oxygen atom of the alcohol to launch a nucleophilic attack on the carboxyl carbon atom, and undergo a series of intermediate conversions to eventually generate esters and water. Since this reaction is a reversible reaction, in order to increase the yield of ethyl acetate, measures such as increasing the concentration of reactants (such as excessive ethanol or acetic acid) or removing the water generated by the reaction in time can be taken to promote the balance to move in the direction of ester formation.

III. Experimental Materials and Instruments
1. ** Experimental Materials **: anhydrous ethanol, glacial acetic acid, concentrated sulfuric acid, saturated sodium carbonate solution, saturated saline, anhydrous magnesium sulfate, zeolite.
2. ** Experimental Instruments **: round bottom flask, reflux condenser, distillation head, straight condenser, connecting pipe, conical bottle, liquid separation funnel, thermometer, alcohol lamp, iron frame table, asbestos net.

IV. Experimental steps
1. ** Construction of reaction device **: In a dry round-bottom flask, add a certain amount of absolute ethanol and glacial acetic acid in sequence, then slowly add concentrated sulfuric acid, shake while adding, mix well and then put in a few zeolites. Next, connect the round-bottom flask with a reflux condenser pipe to set up a reflux device.
2. ** Reflux reaction **: Use an alcohol lamp to heat the round-bottom flask, so that the reaction mixture is kept in a slightly boiling state and refluxed for a period of time. During the reflux process, closely observe the reaction phenomenon and record the reaction temperature and time. After the reflux is completed, stop heating and wait for the reaction mixture to cool to room temperature.
3. ** Product Separation and Purification **: Pour the cooled reaction mixture into the separation funnel, add an appropriate amount of saturated sodium carbonate solution, and gently shake the separation funnel to neutralize the unreacted acetic acid and reduce the solubility of ethyl acetate in water. After standing for stratification, separate the lower aqueous phase. The organic phase is washed again with saturated table salt water to remove the residual sodium carbonate, and then the aqueous phase is separated. Next, transfer the organic phase to a dry conical bottle, add an appropriate amount of anhydrous magnesium sulfate for drying, and leave it for a period of time to allow the moisture to be fully absorbed.
4. ** Distillation Collection Product **: Transfer the dried organic phase to the distillation flask, set up a distillation device, and heat the distillation. Collect the fraction at 73 - 78 ° C. This fraction is the ethyl acetate product. Record the volume or quality of the product for subsequent calculation of the yield.

5. Precautions for experiments
1. Concentrated sulfuric acid is highly corrosive. When adding concentrated sulfuric acid, it must be added slowly and shaken continuously to prevent local overheating from causing liquid splashing.
2. During the reflux reaction, the reaction temperature should be strictly controlled to avoid side reactions caused by excessive temperature, which will affect the yield and purity of ethyl acetate.
3. When using a liquid separation funnel for liquid separation operation, pay attention to the use of cocks to ensure the smooth progress of liquid separation operation and avoid cross-contamination of organic and aqueous phases.
4. During the drying process, the amount of anhydrous magnesium sulfate should be appropriate. Too little water cannot be fully removed. Too much may adsorb part of ethyl acetate, resulting in a decrease in yield.

VI. RESULTS AND DISCUSSION
1. ** Yield calculation **: The yield of ethyl acetate is calculated based on the mass or volume of the ethyl acetate actually collected, combined with the theoretical yield (calculated according to the amount of reactants and the reaction equation). The yield calculation formula is: yield = $\ frac {actual yield} {theoretical yield} $× 100%.
2. ** RESULTS ANALYSIS **: The experimental results are analyzed to explore the factors affecting the yield of ethyl acetate. For example, factors such as the proportion of reactants, reaction time, reaction temperature, catalyst dosage, and loss during product separation and purification may all affect the yield. By comparing with theoretical values, analyze the shortcomings in the experiment and think about improvement measures to optimize the experimental scheme to improve the yield and purity of ethyl acetate. At the same time, provide a reasonable explanation of the phenomenon observed during the experiment to further deepen the understanding of the principle and operation of Fisher's esterification reaction.