Nitrile spices are new spices developed in the past 20 years. In the perfume industry, the aroma and performance of nitrile compounds are better than those of corresponding aldehyde compounds. In addition, nitrile compounds are stable in nature, do not decompose and change color during application, are safe, non-toxic, and have no irritating effect on the skin. They are aldehyde perfumes. ideal substitute. p-Methoxybenzonitrile, commonly known as aniseonitrile, is an important new spice. The traditional synthesis method is to prepare anisaldehyde oxime from anisaldehyde, and then use acetic anhydride to catalyze dehydration to generate anisonitrile. The main shortcomings of this method are: acetic anhydride consumption is large, the purification process is complicated, and the dehydration conversion rate is low. .
Perfluorosulfonic acid resin Nafion NR5O (NR5O for short) has the advantages of high thermal stability (<280°C), chemical inertness and super acidity, and is widely used in the field of catalysis. The solid acid Nafion/SiO2 produced by DuPont shows good catalytic performance for many important chemical reactions. Experimental results show that the solid acid Nafion/SiO2 has many unique advantages: the product has good color, high purity, and is less corrosive to equipment. , has little environmental pollution, uses less catalyst and can be reused, but it is rarely reported in the catalytic synthesis of nitrile spices. Research in recent years has shown that microwave technology has special advantages in organic synthesis and is widely used in nucleophilic substitution, Diele-Alder, elimination reactions, condensation reactions, esterification reactions, alkylation reactions and other organic synthesis. The reaction rate under microwave action is several times or even thousands of times faster than traditional experimental techniques, but its use in nitrile synthesis is rarely reported. This article uses the solid acid Nafion/SiO2 to catalyze dehydration under microwave conditions to synthesize aniseonitrile.
Synthesis of anise aldehyde oxime
In a 250 mL three-necked flask equipped with a thermometer, dropping funnel, and stirrer, first add 100 mL of water, then add an appropriate amount of hydroxylamine hydrochloride in a certain proportion, start stirring and slowly Add sodium carbonate. Powder, when the water bath is heated to 40°C, start adding anisaldehyde dropwise and stir vigorously. 21.3 g (0.15 mol) of anisaldehyde will be dropped in 10 minutes. Then the temperature was raised to about 50°C and stirred vigorously for 2 hours. After the reaction was completed, it was neutralized with acetic acid to about pH=6, and the mixture was cooled to room temperature during stirring until anise aldehyde oxime became a granular solid and then stopped. Stir and let sit for a few hours before filtering. The obtained anisic aldoxime solid is heated in a water bath, vacuum distilled and evaporated to remove the water contained in the aldoxime until the liquid in the bottle no longer bubbles.
Dehydration of anise aldehyde oxime to prepare anise nitrile
Add the anise aldoxime prepared in the previous step into a 150mL polytetrafluoroethylene reaction tank, add an appropriate amount of solid acid Nafion/SiO2 catalyst and solvent benzene, stir well and tighten The jar lid is placed in a microwave oven and reacts with radiation under a certain microwave power. After the reaction is completed, wait for the reaction tank to cool down, open the tank lid, pour out the product and filter, wash the benzene layer (2 × 40 mL) with water, separate the aqueous layer, dry the benzene layer with anhydrous magnesium sulfate, and recover the solvent benzene by distillation under reduced pressure. The remaining After the material is cooled and air-dried, crude aniseed nitrile is obtained.
Refined
Carry out vacuum fractionation of the air-dried crude anisonitrile in a fractionation device. Collect the distillate until the distillate becomes yellow. Melt the distillate and put it into a pot containing acetone. Recrystallize it in a container, heat it until it is completely dissolved, let it cool down and let it stand overnight, filter it under reduced pressure to remove the acetone, and let the crystals air-dry naturally to obtain the product. Its melting point was measured to be 59.3 ~ 6O. 2°C, chromatographic analysis showed that the aniseed nitrile content was 97.8%.
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