N-butyl ether, also known as dibutyl ether, is not only an important fine organic synthesis chemical product, but also a good solvent. N-butyl ether has strong solubility to many natural synthetic oils, resins, rubber, organic esters, alkaloids and hormones, and is an excellent solvent for their extraction and purification. The mixed solution of n-butyl ether and butyl phosphate can be used as a solvent for the separation of rare earths. Because n-butyl ether is an inert solvent, it can also be used as format reagent, reaction solvent for pesticide synthesis, reagent and extractant for the determination of bismuth.
The molecular structure of n-butyl ether is CH3CH2CH2CH2-O-CH2CH2CH2CH3, and the basic structure of the target compound is an ether structure, with ether bonds in the molecule and the basic properties of ether.
Methods for Preparing n-Butyl Ether
There are two main methods for the preparation of n-butyl ether, which are alcohol dehydration and Williamson synthesis, both of which are more practical methods for the synthesis of ether, but the first method is more suitable for the synthesis of monoether and the second method is suitable for the synthesis of mixed ether.
1. Alcohol Dehydration Method
Under acid catalysis, intermolecular dehydration can occur when alcohols are heated to form ethers.
Intermolecular dehydration of alcohols is a common method for the synthesis of monoether, but it is only suitable for the synthesis of primary alcohols. The yield of secondary alcohols is low, while tertiary alcohols mainly undergo intramolecular dehydration to olefins.
2. Williamson Synthesis Method
Sodium alcohols or sodium phenols react with halogenated hydrocarbons to form ethers, which is called Williamson synthesis.
Williamson synthesis is a good method for the synthesis of mixed ethers, but attention should be paid to avoid the use of tertiary haloalkanes when selecting raw materials, because sodium alcohol is a strong base, and tertiary haloalkanes mainly produce olefins by elimination reactions under the action of strong bases.
Synthesis of n-Butyl Ether
Take the synthesis of n-butyl ether by dehydration of alcohol under acid catalysis as an example.
1. Preparation of Instrument and Reagent
1) Instrument
250mL round bottom flask, spherical condensing tube, water separator, thermometer, 120mL liquid separation funnel, 50mL distillation flask, electric sleeve, iron frame platform.
2) Reagent
N-butanol, concentrated sulfuric acid, 5% sodium hydroxide, anhydrous calcium chloride, saturated calcium chloride solution.
2. Experimental Device Construction
The synthesis device can be built with reference to the following figure.
Diagram of reaction equipment for synthesis of n-butyl ether
The main points for installation of the device are as follows.
1) Clamp and fix the three-neck flask first, then connect the water separator and the spherical condensing tube and fix it on the iron platform.
2) The whole experimental device should be installed correctly to ensure that the water separator and the spherical condensing tube are perpendicular to the table, so as to ensure a better separation effect.
3) The mercury ball part of the thermometer should be inserted below the page to observe and control the real-time temperature of the reaction solution.
4) Plug the unused one of the three-port flasks, so as not to affect the yield because of the poor sealing.
5) Check whether the valve of the water divider is sealed in advance to ensure that there is no leakage during the reaction.
Experimental Procedure
1. Operation Steps
The schematic diagram of the operation flow for the synthesis of n-butyl ether is shown in the figure.
Schematic diagram of operation flow for synthesis of n-butyl ether
1) In a 250mL three-necked flask, first add 31mL of n-butanol, and then add 4.5mL of concentrated sulfuric acid into the flask in batches. Each batch is fully shaken. After adding, shake vigorously and fully, and then add several zeolites. An oil-water separator is installed in the middle of the three-port flask, and a thermometer is installed at one side. The thermometer is inserted below the liquid level.
2) Install the three-port flask on the iron stand, and add water carefully along the inner wall opposite the branch pipe mouth of the oil-water separator. Be careful not to let the water flow into the three-port flask until the water surface rises to just flush with the lower edge of the branch pipe mouth. Carefully open the piston, drain 4mL of water, and install the return condensate pipe at the upper end of the oil-water separator.
3) Heat the three-port flask with asbestos screen until it is slightly boiling. After the reaction liquid boils, the steam enters the reflux condensate pipe, and is condensed into a mixed liquid and then drops into the oil-water separator. The water layer sinks and the oil layer floats on the water surface. When the oil level rises to the branch pipe, it will return to the three-port flask. The reaction can be stopped when the reflux is stable until it is flush with the lower edge of the branch pipe mouth. After about 1.5h, the temperature of the reaction solution in the three-necked bottle is 135~137 oC. If the heating is continued, the reaction liquid may become black and there will be more by-product olefins.
4) After slightly cooling, open the piston, drain the water in the oil-water separator, pour the reaction liquid into the separating funnel containing 50mL of water, shake it fully, and then discard the lower liquid after standing for layering. The upper crude product is washed with 25mL of water, 15mL of 5% sodium hydroxide solution, 15mL of water and 15mL of saturated calcium chloride solution in turn, and finally the water layer is separated. The crude product is poured into a clean and dry small conical flask from the top of the funnel, and 1~2g of anhydrous calcium chloride is added, and the bottle mouth is closed and dried for more than 0.5h.
5) Pour the dried crude product into a 50mL round bottom flask, distill and collect the fraction at 140~144 oC, weigh and calculate the yield. The product is a colorless transparent liquid with a yield of about 7~8g and a yield of 31.9%~40%.
2. Calculate Yield
3. Precautions
1) According to the theoretical calculation, the water loss volume in this experiment is 3mL, but the actual volume of water separated is slightly larger than the calculated volume, so about 4mL of water will be discharged first after the water separator is filled with water.
2) The optimum temperature for preparing n-butyl ether is 130~140 oC, but it is difficult to reach this temperature at the beginning of reflux, because n-butyl ether can form a azeotrope with water (boiling point 94.1 oC, water content 33.4%); In addition, n-butyl ether can form a ternary azeotrope with water and n-butanol (boiling point 90.6 oC, water content 29.9%, n-butanol 34.6%), and n-butanol can also form an azeotrope with water (boiling point 93 oC, water content 44.5%), so it should react between 100~115 oC for 0.5h to reach above 130 oC.
3) In the process of alkali washing, do not shake the separating funnel too violently, otherwise it will generate emulsion, which will cause separation difficulties.
4) N-butanol is soluble in saturated calcium chloride solution, while n-butyl ether is slightly soluble.
4. Detection and Identification of Product
The appearance and state of n-butyl ether were observed and the refractive index of n-butyl ether was determined.
