Hydroquinone diethyl ether

Obtained (poor yield) by reaction of 2,3,6-trimethoxy-benzoyl chloride with hydroquinone diethyl ether in ethyl ether in the presence of aluminium chloride at r.t. for 2 days (7%) [1172]. m.p. 100-101° [1172] Spectra (NA). 

Also obtained by condensation of hydroquinone diethyl ether with acetyl chloride according to the Friedel-Ciafls method [3007,3008]. 

Obtained (by-product) by Friedel-Crafts acylation of hydroquinone diethyl ether with propionyl chloride or propionic anhydride in the presence of aluminium chloride, first below 5° and short reflux times [7149]. 

A Methylamino)phenol. This derivative, also named 4-hydroxy-/V-methy1ani1ine (19), forms needles from benzene which are slightly soluble in ethanol andinsoluble in diethyl ether. Industrial synthesis involves decarboxylation of A/-(4-hydroxyphenyl)glycine [122-87-2] at elevated temperature in such solvents as chlorobenzene—cyclohexanone (184,185). It also can be prepared by the methylation of 4-aminophenol, or from methylamiae [74-89-5] by heating with 4-chlorophenol [106-48-9] and copper sulfate at 135°C in aqueous solution, or with hydroquinone [123-31 -9] 2l. 200—250°C in alcohoHc solution (186). 

The strongly oxidizing SbCl5 is an effective oxidant for the preparation of cation-radical salts of hexachloroantimonate (SbCl ) from a variety of organic donors, such as para-substituted triarylamines, fully-substituted hydroquinone ethers, tetraarylethylenes, etc.176 For example, the treatment of the hydroquinone ether EA (2 mmol) with SbCl5 (3 mmol) in anhydrous dichloromethane at — 78°C immediately results in an orange-red solution from which the crystalline cation radical salt readily precipitates in quantitative yield upon the slow addition of anhydrous diethyl ether (or hexane)173 (equation 36). 

The commercial product usually contains appreciable quantities of peroxide this should be removed by treatment with an acidified solution of an iron(n) salt or with a solution of sodium sulphite (see under 15. Diethyl ether). The diisopropyl ether is then dried over anhydrous calcium chloride and distilled, the fraction b.p. 68.5 °C/760 mmHg being collected. Di-isopropyl ether should be stored in brown bottles away from the light. A small amount of hydroquinone (2 x 10 5 m) may be added as a peroxide inhibitor. 

Acrylic acid esters can polymerize readily this must be taken into account during their preparation. Thus, attempts to prepare pentafluorophenyl acrylate from acrylo-yl chloride in the presence of pyridine led to extensive polymerization of the product [24], This polymerization can be prevented by using the less nucleophilic 2,6-dimethylpyridine as base and diethyl ether or pentane instead of THF as solvent (Scheme 7.5). Esterifications of acrylic acid under acidic conditions should be conducted in the presence of small amounts of hydroquinone as radical scavenger. Acrylic acid derivatives can also be prepared by acylation with a propionic acid with a leaving group at C-3 followed by/3-elimination. 

Methods involving LLE were developed for determination of phenol and other phenolic compounds. For example, for simultaneous determination of phenol, hydroquinone (66) and catechol (42) in urine, the samples were subjected to acid hydrolysis, saturation with sodium sulfate and LLE with diethyl ether. End analysis was by RP-HPLC on a Ci8 column, elution with sodium acetate-acetic acid buffer-acetonitrile gradients, and ELD. The recovery and reproducibility were generally over 90%. The method appears to be more sensitive than GC or HPLC with UVD. It is proposed for cigarette smokers and refinery workers exposed to low benzene concentrations. Good recoveries of these metabolites was attained at 0.1 to 50 mgL concentrations, with coefficients of variation of a few percent, both for within a day and between day determinations. ... 

Diisopropyl ether, which is occasionally used in the laboratory as a higherboiling ether, is especially liable to peroxide-formation.16 It is advisable to purify it by filtration through aluminum oxide, as for diethyl ether, and to store it over sodium wire or to stabilize it by addition of 0.001% of pyro-catechol, resorcinol, or hydroquinone.17... 

PEG itself is useful as a phase-transfer catalyst because it is an acyclic analog of a crown ether [86]. This property of PEG and its potential as a support for a substrate were combined in a recent synthesis of monoethers of hydro-quinone and resorcinol [87]. In this chemistry (Eq. 17), a dihydroxyl PEG 4,000 (n=ca. 90) 33 was first allowed to react with an excess of oxalyl chloride. The resulting diacid chloride was then allowed to react with the hydroquinone or resorcinol to form a diester, which was easily isolated by solvent precipitation with diethyl ether. Subsequent treatment of this phenolic ester with an alkyl iodide in the presence of K2CO3 in DMF led to the PEG-bound monoether ester. In this reaction, the PEG acted both as a support and as a phase-transfer catalyst. Subsequent hydrolysis generated the monoether of the hydroquinone or resorcinol. 

To the solution of barium hydroxide (275 g) in distilled water (500 ml), MDP (83 ml) was added over a period of 30 min with constant stirring. The reaction was carried for more than 3 h, while the temperature was maintained below 30 C. After the completion of the reaction, the reaction mixture was acidified with Cone. HCl till the pH of the solution was reduced to 2.0. The compound OC -chloroacrylic acid was then extracted with several portions of a solution containing 1 g of hydroquinone for every 200 ml of diethyl-ether. The ether extract was then dried over anhydrous magnesium sulfate overnight. The product was then isolated by evaporating the ether under reduced pressure. The crude product was recrystallized from hexane at low temperature to get 60 g of -chloroacrylic acid (MP 64-65°C). 

Diethyl ether should be inhibited against peroxide formation in storage and use with an inhibitor of which pyrogallol (0.2% w/w), hydroquinone or other phenols and diphenylamine are possible choices. Storage under nitrogen is very desirable. Samples should be stored in brown bottles with a minimum of ullage. Since all the inhibitors are very much less volatile than diethyl ether, newly distilled material will be iminhibited and should be treated without delay. 

A further consideration is whether the solvent is likely to interfere with the analysis. Toluene is a poor first choice for a method that is to quantify the drug by ultraviolet detection. It is difficult to remove all traces of the solvent, and even a small residual amount can affect the detection limit seriously. Similarly, chlorinated solvents are best avoided if radioactive scintillation counting or electron-capture detection is to be used. Some solvents may not be suitable because they would react with the analyte, for example a ketone such as ethyl methyl ketone would react with primary amines. Solvent impurities and additives may be unknown to the analyst. Antioxidants such as hydroquinone and pyrogallol are added to diethyl ether to limit peroxide formation. These highly electroactive molecules can affect electrochemical detection methods adversely, particularly if they have been concentrated by solvent evaporation. Freshly distilled diethyl ether may be used, but it should not be stored as this is not only potentially dangerous, the peroxides that form may decompose the analyte. Methyl /-butyl ether (boiling point 55°C) is supplied without antioxidants and is a useful alternative to diethyl ether. Chloroform and dichloro-methane may be stabilized with ethanol although pentene is used by at least one manufacturer and may... 

Methacrylic acid (MAA) was obtained from Aldrich Chemicals with 250 ppm inhibitor of methyl ethyl hydroquinone (MEHQ) without further purification. Styrene also came from Aldrich and was double distilled and inhibited with hydroquinone (HQ) before use. Diethyl ether (DEE) from Aldrich Chemicals was used as it is. Poly(methacrylic acid) (PMAA) made by the FRRPP process in our lab with different molecular weights and polydispersity indices (PDI) was used in the experiments. Polystyrene was bought from Pressure Chemicals Co. with different molecular weights and the same PDI of 1.06. The products through the FRRPP process in our lab were also used to determine the phase envelope. 

Into a round bottom flask equipped with nitrogen inlet and mechanical stirrer were added equimolar quantities of the non-cyclic bis(amide-1,3-diene) and bis(4-maleimidylphenyl) methane. Hydroquinone was added as a radical scavenger and 1,1,2,2-tetrachloroethane was added to afford an approximate 30 % (w/w) solution which was stirred at room temperature under a nitrogen atmosphere for 24 h. The reaction temperature was then increased to 140°C and maintained for 24 h. As the viscosity of the solution increased during these reaction periods, small aliquots of the solvent were added to improve stirring. The polymer solution was cooled to room temperature, precipitated by dropwise addition of the reaction mixture into stirred diethyl ether, filtered, and dried under vacuum. Reprecipitation from a chloroform solution into diethyl ether afforded the polyimide. 

The presence of antioxidants in eluents and extraction solvents Antioxidants can be readily oxidized electrochemically and generate high background currents or interfering broad peaks. Thus, eluents and extraction solvents containing such compounds should be either avoided or purified before use. For example, ethers, such as diethyl ether, diisopropyl ether, and tetrahydrofuran are likely to contain up to 0.1% (w/v) pyrogallol or quinol (hydroquinone) as stabilizer. If the stabilizer is removed, peroxides will form and their concentration will increase with time unless the solvent is stored under nitrogen. Not only do peroxides present a hazard from explosion, but they may also oxidize susceptible analytes. Methyl f-butyl ether (MTBE), on the other hand, is stable to oxidation. 

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