Dimethoxybenzene is an important chemical raw material, widely used in medicine, pesticide, spice and other fields. There are two main manufacturing methods: one is obtained by the reaction between phenol and dimethyl sulfate, and the other is obtained by the methylation reaction between benzene and methanol in the presence of acid catalyst. This article will introduce these two manufacturing methods in detail.
I. Phenol and Dimethyl Sulfate Reaction Method
1. Raw Material Preparation
Phenol: colorless needle crystal with special smell, easily soluble in hot water, ethanol, ether and other organic solvents.
Dimethyl sulfate: colorless transparent liquid, with irritating odor, easily soluble in water and organic solvents.
2. Reaction principle
Under the action of alkaline catalyst, phenol and dimethyl sulfate undergo substitution reaction to produce dimethoxybenzene.
3. Procedure
(1) Mix phenol with alkaline catalyst and heat to a certain temperature.
(2) Slowly add dimethyl sulfate dropwise, control the rate of dropwise acceleration and keep the reaction temperature stable.
(3) After the dropwise addition, continue the reaction for a certain time, and then cool to room temperature.
(4) Adjust the pH to neutral with acid and separate the unreacted phenol and sodium sulfate salt.
(5) The organic phase was washed with distilled water, dried and then distilled to collect the fraction of dimethoxybenzene.
4. Precautions
(1) Dimethyl sulfate is toxic, and the operation requires strict control of the titration rate and avoiding local overheating.
(2) Alkaline environment needs to be maintained during the reaction to promote the reaction.
(3) The temperature needs to be controlled during distillation to avoid the decomposition of dimethoxybenzene.
II. Benzene and methanol methylation reaction method
1. Raw material preparation
Benzene: colorless transparent liquid with special smell, insoluble in water, easily soluble in organic solvents.
Methanol: colorless transparent liquid, with alcohol flavor, soluble in water and organic solvents.
Acidic catalyst: such as sulfuric acid, phosphoric acid, etc.
2. Reaction principle
In the presence of acidic catalyst, benzene and methanol undergo methylation reaction to produce dimethoxybenzene.
3. Procedure
(1) Mix benzene, methanol and acid catalyst and heat to a certain temperature.
(2) Stir continuously during the reaction to maintain the homogeneity of the reaction solution.
(3) After the reaction is completed, cool to room temperature and adjust the pH to neutral with alkali.
(4) The unreacted benzene and methanol were separated and the organic phase was washed with distilled water and dried.
(5) Distillation was carried out to collect the fraction of dimethoxybenzene.
4. Precautions
(1) The selection of acidic catalyst has an important influence on the reaction rate and selectivity, and a suitable catalyst needs to be selected according to the specific conditions.
(2) A certain temperature and pressure need to be maintained during the reaction to promote the reaction.
(3) The temperature needs to be controlled during distillation to avoid the decomposition of dimethoxybenzene.
The above two manufacturing methods can obtain dimethoxybenzene, but each has its own advantages and disadvantages. Phenol and dimethyl sulfate reaction method is easy to obtain raw materials, operation is relatively simple, but dimethyl sulfate is toxic, need to strictly control the operating conditions. Benzene and methanol methylation reaction method is green raw materials, but the reaction conditions are more demanding, requiring higher temperature and pressure. In actual production, the appropriate manufacturing method can be selected according to the specific circumstances.
