Method for synthesizing 3,5-dichlorobenzoic acid

Abstract

The invention discloses a method for synthesizing 3,5-dichlorobenzoic acid, which comprises the following steps: chlorinating benzonitrile used as a raw material to generate 3,5-dichlorobenzonitrile; and then, performing hydrolysis and acidification reaction to obtain 3,5-dichlorobenzoic acid. According to the invention, the benzonitrile is used as the raw material; sodium hypochlorite or a mixture of oxydol and hydrochloric acid is used in the chlorination process; the traditional chlorine gas chlorination process is omitted; the obtained 3,5-dichlorobenzonitrile is high in purity; no diazotization procedure is required; and the process safety is enhanced. The process has the advantages of accessible and cheap raw material, low production cost of the product, high process safety coefficient and short process flow, is simple to operate, is more beneficial to industrial production, is a new process for synthesizing 3,5-dichlorobenzoic acid, and provides a new idea for synthesizing propyzamide.

Description

technical field

[0001] The invention relates to a method for synthesizing 3,5-dichlorobenzoic acid, in particular to a method for synthesizing 3,5-dichlorobenzoic acid using benzonitrile as a starting material. Background technique

[0002] Haloformic acid and its derivatives are a class of important chemical and pharmaceutical intermediates, which are widely used as raw materials for the production of fungicides, insecticides, dyes and drugs. 3,5-Dichlorobenzoic acid is one of them. Used in the preparation of various chemical products such as medicines, pesticides, dyes, and fungicides. In recent years, the demand for this product has been increasing year by year, and the development and research have gradually attracted people's attention.

[0003] The synthetic method of 3,5-dichlorobenzoic acid reported at present has following two kinds by raw material classification:

[0004] One is to use 3,5-diaminotoluene as raw material, first diazotize to generate 3,5-dichloroto...

Examples

Embodiment 1

[0027] Add 300g of chloroform and 100g of ethanol to 100.0g of benzonitrile (content 99%), and then add 1209.4g of sodium hypochlorite (content 13%), use 37% hydrochloric acid to keep the pH of the system at 3.0-4.0, at 55-60 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.5%, then add 30% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 12-13, and keep the reaction at 80-90℃ After 2.5 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 1.0, react at 50-60°C for 1.0h, filter again, and dry at 90-110°C to obtain 182.5g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

Embodiment 2

[0029] Add 1500g chloroform and 500g ethanol to 100.0g benzonitrile (content 99%) respectively, then add 1209.4g sodium hypochlorite (content 13%), use 98% sulfuric acid to keep the pH value of the system at 5.0-6.0, at 60-70 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.4%, and then add 20% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 11-12, and keep the reaction at 80-90℃ After 3.0 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 0, react at 50-60°C for 0.5h, filter again, and dry at 90-110°C to obtain 182.5g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

Embodiment 3

[0031] Add 75g of chloroform and 25g of ethanol to 100.0g of benzonitrile (content 99%), and then add 1209.4g of sodium hypochlorite (content 13%), use 25% hydrochloric acid to keep the pH value of the system at 0-1.0, at 55-70 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.5%, then add 10% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 13-14, and keep the reaction at 80-90℃ After 2.7 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 1.5, react at 50-60°C for 0.6h, filter again, and dry at 90-110°C to obtain 182.3g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

technical field

[0001] The invention relates to a method for synthesizing 3,5-dichlorobenzoic acid, in particular to a method for synthesizing 3,5-dichlorobenzoic acid using benzonitrile as a starting material. Background technique

[0002] Haloformic acid and its derivatives are a class of important chemical and pharmaceutical intermediates, which are widely used as raw materials for the production of fungicides, insecticides, dyes and drugs. 3,5-Dichlorobenzoic acid is one of them. Used in the preparation of various chemical products such as medicines, pesticides, dyes, and fungicides. In recent years, the demand for this product has been increasing year by year, and the development and research have gradually attracted people's attention.

[0003] The synthetic method of 3,5-dichlorobenzoic acid reported at present has following two kinds by raw material classification:

[0004] One is to use 3,5-diaminotoluene as raw material, first diazotize to generate 3,5-dichloroto...

Examples

Embodiment 1

[0027] Add 300g of chloroform and 100g of ethanol to 100.0g of benzonitrile (content 99%), and then add 1209.4g of sodium hypochlorite (content 13%), use 37% hydrochloric acid to keep the pH of the system at 3.0-4.0, at 55-60 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.5%, then add 30% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 12-13, and keep the reaction at 80-90℃ After 2.5 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 1.0, react at 50-60°C for 1.0h, filter again, and dry at 90-110°C to obtain 182.5g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

Embodiment 2

[0029] Add 1500g chloroform and 500g ethanol to 100.0g benzonitrile (content 99%) respectively, then add 1209.4g sodium hypochlorite (content 13%), use 98% sulfuric acid to keep the pH value of the system at 5.0-6.0, at 60-70 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.4%, and then add 20% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 11-12, and keep the reaction at 80-90℃ After 3.0 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 0, react at 50-60°C for 0.5h, filter again, and dry at 90-110°C to obtain 182.5g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

Embodiment 3

[0031] Add 75g of chloroform and 25g of ethanol to 100.0g of benzonitrile (content 99%), and then add 1209.4g of sodium hypochlorite (content 13%), use 25% hydrochloric acid to keep the pH value of the system at 0-1.0, at 55-70 At ℃, react until the content of 3,5-dichlorobenzonitrile is 99.5%, then add 10% sodium hydroxide under normal pressure to keep the pH value of the reaction system at 13-14, and keep the reaction at 80-90℃ After 2.7 hours, acidify the system with 37% hydrochloric acid until the pH value of the system is 1.5, react at 50-60°C for 0.6h, filter again, and dry at 90-110°C to obtain 182.3g of 3, with a content of 99.0%. 5-Dichlorobenzoic acid.

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