The reaction of alcohols and organic acids catalyzed by acids to form esters is called esterification.
Commonly used catalysts are sulfuric acid, hydrogen chloride, or benzenesulfonic acid.
Since the esterification reaction of organic acids is reversible, to increase the yield of esters, the reaction must be carried out to the right.
One approach is to increase the amount of one reactant to change the composition of the reactant and product when the reaction reaches equilibrium.
Another method is to continuously remove a product from the reaction system to shift the equilibrium to the right. Commonly used are: ① use an azeotropic mixture to remove water, ② add a suitable dehydrating agent to remove the water produced by the reaction.
Details can be found in this official account tweet Preparation of ethyl benzoate.
Recently on the official account, many middle school students have left messages asking us to introduce the experimental projects in the middle school stage. Therefore, this article has selected "Preparation of Ethyl Acetate", an organic synthesis reaction that is also offered in the high school stage. Briefly introduce the difference between the requirements of the same synthesis reaction in the middle school stage and the requirements in the university stage (please bear with me if there is any inaccuracy or incompleteness).
The reaction equation (both high school and college use the same synthetic route):
| Middle school | 1. Learn how to prepare ethyl acetate | 2. Understanding the preparation experiment of ethyl acetate from the principle of equilibrium movement | |
|---|---|---|---|
| College level | 1. General methods for learning esterification reactions: Thinking and learning about measures to improve the yield of esters from esterification reactions | 2. General operations for consolidating the synthesis, separation and purification of liquid compounds: washing, extraction, drying, distillation and purification, etc. | 3. Learn and master the identification and characterization of organic compounds: determination of physical constants such as boiling point determination, characterization of molecular structures such as infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, etc. |
The middle school stage is mainly based on students' observation experience, and no more in-depth requirements are made for the purification of compounds.
Although the preparation experiment of ethyl acetate in the university stage is simple, it basically provides a complete thinking training for the whole process of organic synthesis reaction. Each step of learning such as synthesis route design, synthesis process design, purification operation, and structure characterization is the deepening and application training of knowledge.
People's Education Edition Elective 5 Experimental Installation Diagram
Heating Reflux Unit 1, Distillation Unit 2, Solution Wash Extraction 3 Involved in University Preparation of Ethyl Acetate
| Middle School | University | |
|---|---|---|
| reaction | 1. Feeding: In the test tube, add absolute ethanol first, then concentrated sulfuric acid, and finally glacial acetic acid | 1. Ingredients: Add absolute ethanol (0.2 mol) and glacial acetic acid (0.1 mol) to a round bottom flask, then carefully add concentrated sulfuric acid, add zeolite, and install a condenser |
| 2. Heating: heating simple reflux, steam out ethyl acetate while reacting | 2. Heat on low heat: maintain reflux for 0.5h | |
| Post-processing | Product ethyl acetate collected with saturated sodium carbonate solution | 3. Distillation: Distilled ethyl acetate |
| 4. Solution washing: distillate (crude product) is washed with saturated sodium carbonate solution until no carbon dioxide gas is produced; transferred to a separation funnel to separate the water layer; the organic layer is washed with saturated salt water, saturated calcium chloride solution, and water to separate the underlying liquid | ||
| 5. Drying: Pour the organic layer into a drying cone and dry with anhydrous magnesium sulfate | ||
| 6. Distillation: Transfer the dried liquid to a round bottom flask, distill, and collect the 73-78 ° C fraction |
| Boiling point/℃ | Ethyl acetate | Ethanol | Water |
|---|---|---|---|
| 70.2 | 82.6 | 8.4 | 9.0 |
| 70.4 | 91.9 | / | 8.1 |
| 71.8 | 69 | 31 | / |
1. In the college entrance examination questions in previous years, there have also been experiments on the synthesis of ester compounds, such as the synthesis of isoamyl acetate. For the preparation of general ester compounds, the synthesis and purification ideas can refer to the above-mentioned synthesis process of ethyl acetate. Hope this introduction is helpful to junior high school students.
2. For normal students majoring in chemistry in colleges and universities, they should also analyze and study the connection of relevant chemistry knowledge at the middle school and university levels to improve their disciplinary and business capabilities.
Finally, I wish the country peace and stability! Students have achieved academic success and all the best!
