Hydroquinone monomethyl

The polymeric products can be made to vary widely in physical properties through controlled variation in the ratios of monomers employed in thek preparation, cross-linking, and control of molecular weight. They share common quaHties of high resistance to chemical and environmental attack, excellent clarity, and attractive strength properties (see Acrylic ester polymers). In addition to acryHc acid itself, methyl, ethyl, butyl, isobutyl, and 2-ethylhexyl acrylates are manufactured on a large scale and are available in better than 98—99% purity (4). They usually contain 10—200 ppm of hydroquinone monomethyl ether as polymerization inhibitor. 

Acrylonitrile will polymerize violendy in the absence of oxygen if initiated by heat, light, pressure, peroxide, or strong acids and bases. It is unstable in the presence of bromine, ammonia, amines, and copper or copper alloys. Neat acrylonitrile is generally stabilized against polymerization with trace levels of hydroquinone monomethyl ether and water. 

Photo grade contains 0.01—0.02% of a hydroquinone monomethyl or benzyl ether to prevent the oxidation of the alcohol to benzaldehyde. 

Encouraged by the short synthesis of K vitamins, the chromium-mediated benzannulation was extended to the synthesis of vitamin E 68 [59]. The problem of imperfect regioselectivity of alkyne incorporation - which did not hamper the approach to vitamin K due to the final oxidation to the quinone - was tackled by demethylation of both regioisomeric hydroquinone monomethyl ethers 67 to give the unprotected hydroquinone. Subsequent ring closure yielded a-tocopherol (vitamin E) 68 (Scheme 39). 

Fig. 131.—The reciprocal melting point plotted against the volume fraction of diluent for cellulose tributyrate in benzo-phenone ( ), in hydroquinone monomethyl ether (O), and in ethyl laurate (A). (Mandelkern and Flory. )...

Standard on Explosion Prevention Systems, National Fire Protection Association, 2002). For example, methyl acrylate and ethyl acrylate are commonly stabilized with hydroquinone monomethyl ether. Industry guidance recommends a minimum concentration of 5 vol % 02 in the atmosphere above the acrylate to prevent polymerization (Intercompany Committee for the Safety and Handling of Acrylic Monomers, Acrylate Esters, A Summary of Safety ana Handling, 3d ed., 2002). 

Note Acrylamide may contain the following impurities acetamide, acrylic acid, acrylonitrile, copper, formaldehyde, hydroquinone, methylacrylamide, hydroquinone monomethyl ether, peroxide, propanamide, and sulfate. When acrylamide is produced using a copper catalyt, copper salts may be added to aqueous solutions at concentrations >2 ppm (NICNAS, 2002). Commercial solutions 30-50%) are usually inhibited with copper salts to prevent polymerization. In addition, solutions containing oxygen will prevent polymerization. 

Note Inhibited with 35-45 ppm hydroquinone monomethyl ether to prevent polymerization during storage and transport (Acros Organics, 2002). Commercial grades may contain the following impurities acetone and acetonitrile (300-500 ppm), acetaldehyde and propionaldehyde (300-500 ppm), acrolein, methanol, isopropanol and hydrogen cyanide (300-500 ppm) (NICNAS, 2000)... 

Note Hydroquinone monomethyl ether (0.02 wt %) is added to prevent polymerization (Gillette et al, 1952). 

Note Inhibited with 10 to 20 ppm hydroquinone monomethyl ether to prevent polymerization (Acros Organics, 2002). 

Chivers CP Two cases of occupational leuco-derma following contact with hydroquinone monomethyl ether. Br J Ind Med 29 105-107, 1972... 

Acrylonitrile of 99.5-99.7% purity is available commercially, with the following specifications (ppm by weight, maximum) acidity (as acetic acid), 10 acetone, 75 acetonitrile, 300 acrolein, 1 hydrogen cyanide, 5 total iron, 0.1 oxazole, 10 peroxides (as hydrogen peroxide), 0.2 water, 0.5% and nonvolatile matter, 100. Hydroquinone monomethyl ether (MEHQ) is added as an inhibitor at concentrations of 35-45 mg/kg (ppm) (Cytec Industries, 1994, 1997). Trade names for acrylonitrile include Acritet, Acrylon, Carbacryl, Fumigrain and Ventox. 

Vinylidene chloride is a central ncr ous system depressant. Repeated exposure to low concentrations of vinylidene chloride may cause liver and renal dysfunction (Torkelson Rowe, 1981). Skin contact with vinylidene chloride causes irritation, which may be due partly to the presence of an inhibitor, hydroquinone monomethyl ether (Chivers, 1972). In one study, spirometry, blood clinical chemistry for liver and renal toxicity, haematological parameters and blood pressure measurements did not differ between vinylidene chloride-exposed workers and controls. Measured past time-weighted average vinylidene chloride concentrations ranged from < 5 to 70 ppm [< 20-280 mg/m- ] (Ott et al., 1976). 

Allyl-2-methoxy phenol. (10) Hydroquinone monomethyl ether. 

Calibration Curve Transfer 25.0 mg of hydroquinone monomethyl ether, accurately weighed, into a 100-mL volumetric flask, add Antioxidant-Free Ethyl Acrylate to volume, and shake to effect complete solution (250 p,g/mL). Prepare a series of standards by transferring 1.0-, 5.0-, 10.0-, and 20.0-mL portions of this solution into separate 25-mL volumetric flasks, diluting each to volume with Antioxidant-Free Ethyl Acrylate, and mixing. One milliliter of each of the standards contains 10, 50, 100, and 200 (ig, respectively, of hydroquinone monomethyl ether. Transfer 5.0 mL of each solution into separate 50-mL volumetric flasks, dilute each to volume with isooctane, and mix. Determine the absorbance of each... 

Procedure Transfer 5.0 mL of sample, accurately weighed, into a 50-mL volumetric flask, dilute to volume with isooctane, and mix. Determine the absorbance of this solution in a 1-cm silica cell at 292 nm with a suitable spectrophotometer, using a 1 10 dilution of Antioxidant-Free Ethyl Acrylate in isooctane as the blank. From the previously prepared Calibration Curve read the micrograms of hydroquinone monomethyl ether corresponding to the absorbance of the sample solution, and record this value as w. Calculate the milligrams per kilogram of hydroquinone monomethyl ether (mg/kg HMME) in the sample by the formula... 

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