Chlorophenoxyethoxyethanols From Polychlorobenzenes

Abstract

There are numerous references in the literature to the synthesis of various halophenoxyethanols, or ethylene glycol halophenyl ethers, by the reaction of sodium halophenates with ethylene chlorohydrin (1-4). The corresponding esters have also been reported, including acetates, methacrylates, crotonates, maleates, and cinnamates (4-7).Another procedure used less frequently for the synthesis of halophenoxyethanols involves the condensation of halophenols with ethylene oxide (3, 5). By this method 2-(pentachlorophenoxyethoxy) ethanol and 2-(pentachlorophenoxyethoxyethoxy)ethanol, the analogous derivatives of diethylene glycol and triethylene glycol, respectively, were prepared. In one instance 2-(2,4-dichlorophenoxyethoxy)ethanol was made by the reaction of sodium 2,4-dichlorophenate with diethylene glycol chlorohydrin (8). The acetates of these compounds have also been reported (9). This paper is concerned with the synthesis of chlorophenoxyethoxyethanols and chlorophenoxyethoxyethoxyethanols by the condensation of polychlorobenzenes with diethylene glycol and triethylene glycol, respectively, in the presence of sodium hydroxide and an excess of the glycol.The hydrolysis of 1,2,4,5-tetrachlorobenzene with sodium hydroxide in solution of methanol at 160°in an autoclave (10) yields 2,4,5-trichlorophenol. This phenol is also formed from 1,2,4,5-tetrachlorobenzene when ethylene glycol and propylene glycol are used as solvents at 170-200°at atmospheric pressure (11).Investigation of this reaction using diethylene glycol as solvent at 200°g ave 2,4,5-trichlorophenol (I) as the major product, and a small amount (5 %) of an oil obtained as a steam-distillation residue. Lower reaction temperatures favored the formation of an intermediate compound, 2-(2,4,5-trichlorophenoxyethoxy)ethanol (II). At 125°u sing 1,2,4,5-tetrachlorobenzene and sodium hydroxide in a molar ratio of 1 to 2.5, the maximum alkali consumption was 1.1 moles as determined by titration of hydroxyl ion during the course of the reaction. Onetenth mole of 2,4,5-trichlorophenol was isolated from the reaction mixture corresponding to a yield of 10%. This was subsequently confirmed in a larger scale experiment, in which an 11 % yield of the phenol and 72.5% of 2-(2,4,5trichlorophenoxyethoxy) ethanol were obtained. This compound was esterified with acetic anhydride to give 2-(2,4,5-trichlorophenoxyethoxy) ethyl acetate (III) in 91.6% yield.

Aromatic and Alkaromatic Chlorocarbons

“…In other cases, pentachlorophenol ethers are obtained; for example, boiling potassium hydroxide in ethanol gives a 95% yield of the ethyl ether [74]. Similar results are obtained with sodium hydroxide in triethyleneglycol at 200 0 [230] or in methanol at 120° [186] giving, respectively, the hydroxyphenol ether and pentachloroanisole. It has recently been found that when the reaction with sodium hydroxide is carried out in dimethylsulphoxide (DMSO) at 110-120° a 97% of pentachlorophenol is obtained [231].…”

Carbodiimides

“…The preparation and study of this functional group has been gaining interest because of its application as a condensing agent. Substituted carbo diimides have been applied to the synthesis of amidines, anhydrides, amides, carboxylic acids, sulfonic acids, esters, and other functional groups [2]. Other reviews are also worth considering [2][3][4][5].…”

“…The first review of carbodiimides was published in 1953 [la], and a more recent one appeared in 1967 [lb]. The synthesis of peptide linkages with the aid of carbodiimides has also attracted a great amount of interest [2]. Substituted carbo diimides have been applied to the synthesis of amidines, anhydrides, amides, carboxylic acids, sulfonic acids, esters, and other functional groups [2].…”