(1) Esterification is a reversible reaction. To increase the yield of esters, the reaction must be directed in a direction favorable to ester formation. This is generally achieved by using an excess of reactants to promote the forward reaction. Under laboratory conditions, an excess of ethanol is typically used. High-concentration ethanol is required; anhydrous ethanol is preferable to 95% ethanol. The amount of concentrated sulfuric acid used for catalysis is very small; generally, 3% of the ethanol mass is sufficient. However, to remove the water generated during the reaction, a slightly larger amount of concentrated sulfuric acid should be used.
(2) The reaction temperature for preparing ethyl acetate should not be too high, ideally maintained at around 60℃～70℃. Excessive temperature will produce impurities such as diethyl ether and sulfurous acid. After the liquid boils, heating should be reduced to a low flame. A few pieces of broken porcelain can be added to the test tube beforehand to prevent bumping.
(3) The gas delivery tube should not be inserted into the Na2CO3 solution to prevent uneven heating from causing the Na2CO3 solution to be drawn back into the test tube containing the reactants.
Concentrated sulfuric acid acts as both a catalyst and a dehydrating agent.
The role of saturated Na₂CO₃ solution is: (1) Saturated sodium carbonate solution condenses ester vapor, reduces the solubility of the ester in water (facilitating layering), removes acetic acid mixed in ethyl acetate, and dissolves ethanol mixed in ethyl acetate. (2) Na₂CO₃ reacts with the volatilized acetic acid to produce odorless sodium acetate, making it easier to smell the aroma of ethyl acetate. (3) Ethyl acetate has low solubility in salt solutions. (4) Salt solutions have a high density, facilitating layering.
To promote the formation of ethyl acetate, the following measures can be taken: (1) When preparing ethyl acetate, the reaction temperature should not be too high, and should be maintained at 60℃～70℃. The liquid should not be allowed to boil. (2) It is best to use glacial acetic acid and anhydrous ethanol. Simultaneously, use an excess of ethanol. (3) The amount of concentrated sulfuric acid used for catalysis is very small, but to remove the water generated in the reaction, the amount of concentrated sulfuric acid should be slightly more than the amount of ethanol. (4) Use inorganic salt Na₂CO₃ solution to absorb the volatilized acetic acid.
