Preparation method for 2,4-dichlorophenoxyacetic acid
A technology of dichlorophenoxyacetic acid and dichlorophenoxyacetic acid ester is applied in the field of preparation of 2,4-dichlorophenoxyacetic acid, and can solve problems such as low conversion rate and yield, incomplete reaction, adverse effects and the like , to achieve the effect of improving the conversion rate and yield of the reaction, reducing the reaction time and completing the reaction
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Embodiment 1
[0033] 200g of ethanol, 95g (1mol) of chloroacetic acid and 0.1g of concentrated sulfuric acid were mixed and stirred, and desolvated and dehydrated for 5h to obtain ethyl chloroacetate. 164g (1mol) of 2,4-dichlorophenol, 125g (1mol) of aqueous sodium hydroxide solution with a mass fraction of 32%, and 300g of DMF were mixed and stirred, heated and dehydrated to obtain a DMF solution of sodium 2,4-dichlorophenolate. Add the obtained ethyl chloroacetate to the DMF solution of sodium 2,4-dichlorophenate, stir for 0.5 h, add 200 g of water, separate layers, transfer the upper oil phase to a hydrolysis reactor, and add hydrogen with a mass fraction of 32% Sodium oxide aqueous solution 125g (1mol) was refluxed and stirred for 0.5h, added 130g of 30% hydrochloric acid, crystallized at 10°C for 1h, filtered, and the filter cake was dried to obtain 220g of 2,4-dichlorophenoxyacetic acid as a solid, with a purity of 99.2%, and a yield of 98.8 %.
Embodiment 2
[0035] 200g of methanol, 95g (1mol) of chloroacetic acid and 0.1g of concentrated sulfuric acid were mixed and stirred, and desolvated and dehydrated for 5h to obtain methyl chloroacetate. 164g (1mol) of 2,4-dichlorophenol, 113g (1mol) of potassium hydroxide aqueous solution with a mass fraction of 50%, and 300g of DMAC were mixed and stirred, heated and dehydrated to obtain a DMAC solution of sodium 2,4-dichlorophenolate. Add the obtained methyl chloroacetate to the DMAC solution of potassium 2,4-dichlorophenate, stir for 0.4 h, add 200 g of water, separate layers, transfer the upper oil phase to a hydrolysis reactor, add 130 g of 30% hydrochloric acid, and reflux Dealcoholized for 3 hours, crystallized at 10°C for 1 hour, filtered, and the filter cake was dried to obtain 219 g of 2,4-dichlorophenoxyacetic acid as a solid, with a purity of 99.5% and a yield of 98.6%.
Embodiment 3
[0037] 300g of isooctyl alcohol, 140g (1mol) of bromoacetic acid and 0.1g of concentrated sulfuric acid were mixed and stirred, and desolvated and dehydrated for 4 hours to obtain isooctyl bromoacetate. 164g (1mol) of 2,4-dichlorophenol, 125g (1mol) of 32% sodium hydroxide aqueous solution, 100g of DMSO, and 200g of isopropanol were mixed and stirred, heated and dehydrated to obtain a sodium 2,4-dichlorophenolate solution. Add the obtained isooctyl chloroacetate to the sodium 2,4-dichlorophenolate solution, stir for 0.6h, add 200g of water, separate layers, transfer the upper oil phase to a hydrolysis reactor, add 20g of concentrated sulfuric acid, and reflux dealcoholization 3h, crystallized at 10°C for 1h, filtered, and dried the filter cake to obtain 221g of 2,4-dichlorophenoxyacetic acid as a solid, with a purity of 99.3% and a yield of 99.3%.
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