Purpose of the experiment

1. Understand the basic principles and methods of acid-catalyzed synthesis of organic acid esters;

2. Master the basic operations of reflux water separation, washing, drying, etc.

Experimental Principle

The esterification reaction is a typical acid-catalyzed reversible reaction. In order to increase the yield of the esterification reaction, the method of increasing the amount of a reactant or removing the ester or water of the product is usually used to make the reaction proceed in the direction of generating esters. In this experiment, the water in the product is removed to increase the yield of esters.

Equipment and drugs required for experiments

Key steps and operation points

1. Add 11.5 mL of n-butanol and 7.2 mL of glacial acetic acid to a 50 mL round bottom flask, add 2 drops of concentrated sulfuric acid and mix well;

2. Installation of the instrument: Fix the round-bottomed flask based on the heating jacket; install the water separator and the spherical condenser pipe in sequence from bottom to top, and fix 1/2 of the spherical condenser pipe with an iron clip; add water to the branch pipe of the water separator in advance, and the water surface is about 2 mm lower than its branch pipe;

3. The reaction proceeds: first through condensed water and then heated;

After heating for a period of time, there will be a backflow phenomenon at the lower pipe mouth of the spherical condenser, and the reflux speed is controlled to be 1 to 2 drops/second; at the same time, an oil layer will appear above the water surface in the branch pipe of the water separator (the oil layer is colorless and transparent, and it is insoluble with water). As the reaction progresses, the water surface gradually rises and the oil layer gradually becomes thinner (if the water surface has risen to the branch pipe mouth, a few drops of water need to be released from the piston at the lower end of the water separator to ensure that the thickness of the oil layer is maintained at about 2 mm).

When the thickness of the oil layer is basically unchanged, the reaction has reached equilibrium. Remove the heat source and remove the device after the flask cools; combine the oil layer above the water surface of the water separator with the reaction liquid in the flask to obtain a crude product;

4. Washing product: Pour the coarse product into the separation funnel and wash it with 10 mL of water, 10 mL of 10% sodium carbonate solution, and 10 mL of water respectively. The use of the separation funnel is as follows:

• (1) Pour the washing liquid and the liquid to be washed into the separation funnel from the top, and let it stand on the iron ring to wait for delamination;
• (2) Oscillation operation: Hold the upper mouth and neck of the separation funnel with your left hand and press the grinding port plug, hold the cock under the separation funnel with your right hand, and oscillate back and forth several times;
• (3) Outgassing operation: After oscillation, gas will be generated inside the liquid separation funnel. In order to ensure the balance of internal and external pressure, the cock needs to be opened to release the gas. When outgassing, care should be taken to keep the liquid separation funnel tilted, with the lower mouth slightly upward and facing no one in the fume hood. Gently open the cock (remember that the upper mouth of the liquid separation funnel should be tilted downward at this time, and there should be no liquid at the lower mouth);
• (4) Repeat the oscillation and deflation several times, place the liquid separation funnel on the iron ring for a while, and wait for the liquid to divide into two clear layers before separating;
• (5) Separation operation: Remove the upper piston and open the cock, release the lower liquid from the lower port of the separation funnel, and then pour the upper liquid from the upper port.

5. Dry the product: place the coarse product in a clean conical bottle, add a spoonful of anhydrous magnesium sulfate to it, shake it, and let it stand for a while until the liquid is clear and transparent; gently shake the conical bottle to see if there is a solid desiccant at the bottom of the container and can slide freely. If so, it means it has been dried well, otherwise you still need to add desiccant;

6. Distillation products: Slowly pour the dried liquid into a dry 50 mL round bottom flask (be careful not to pour the desiccant!), add zeolite, install an ordinary distillation device, collect the fraction at 124~ 126 ° C, measure the volume, and calculate the yield and yield according to the specific gravity (density).

Precautions

Water separators and separation funnels should be tested for leaks with water before use.