Phenylarsine oxide

Phenylmagnesium bromide is prepared in the usual manner [Org, Syntheses Coll. Vol. 1, 550 (1941)] from 52 g. (0.33 mole) of bromo-benzene and 7.2 g. (0.30 gram atom) of magnesium. To the solution of the Grignard reagent in ether is added a solution of 38.8 g. (0.2 mole) of anthrone [Org. Syntheses Coll. Vol. 1, 60 (1941)] in dry thiophene-free benzene. Excess ice and dilute hydrochloric acid are added, the ether layer is separated, and the aqueous layer is extracted with ether. The combined ethereal solutions are washed with 12% aqueous alkali solution and water. The ether is evaporated, and the residue is steam-distilled. The residue from the steam-distillation vessel is taken up in ether, and the ether is evaporated. The residual syrup is heated with a mixture of 12% aqueous sodium hydroxide and 10 g. of sodium hydrosulfite. The mixture is cooled and diluted with ether the alkaline aqueous layer is separated and discarded the ethereal layer is washed thoroughly with water and the ether is evaporated. The residual 9-phenylanthracene is reciystallized from acetic acid to give 36 g. (71%) of product, m.p. 152-153°. 

A mixture of 1 part of phenylarsonic acid [Org. Syntheses Coll. Vol. 2, 494 (1943)], 5 parts of methanol, 2 parts of concentrated hydrochloric acid, and a small amount (about 0.1 g.) of potassium iodide dissolved in a small amount of water is treated with sulfur dioxide gas with agitation until the mixture is saturated with sulfur dioxide. Hood.) The mixture is diluted with water, and the oily layer of phenyldichloroarsine is separated and washed thoroughly with water by decantation. 

The phenyldichloroarsine should be handled with extreme caution since it is a powerful vesicant (blistering agent). 

The phenyldichloroarsine is stirred with warm excess 10% aqueous sodium hydroxide until all is in solution. Neutralization of the resulting solution with hydrochloric acid precipitates phenylarsine oxide. This is removed by filtration, washed with water, and dried. There is obtained an 80% yield (based on phenylarsonic acid) of product melting at 144-146°. 

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Use of a pH buffer of 8—9 has been suggested as a substitute for the pH 7 buffer for more accurate analysis. Sodium thiosulfate [10102-17-7] Na2S202, or phenylarsine oxide [637-03-6] C H AsO, are the typical titrants. 

Abbreviations DEPC, diethylpyrocarbonate DCCD, Af.iV -dicyclohexylcarbodiimide EEDQ, N-ethyoxycarbonyl-2-ethoxy-1,2-dihydroquinoline NEM, A-ethylmaleimide PAO, phenylarsine oxide NPM, IV-phenylmaleimide PLP, pyridoxal phosphate DIDS, diisothiocyanostilbene disulfonate PITC, phenylisothiocyanate. 

Kulanthaivel et al. [28] found that the apical Na /H exchanger in human placenta (sensitive-type) was sensitive to phenylarsine oxide, a reagent specific for dithiols that are situated in close proximity (vicinal dithiols). Moreover, the effect of phenylarsine oxide was to decrease without affecting apparent affinity for... 

Urine CVAA Solid phase microextraction headspace sampling, followed by GC/MS with El ionisation Deuterated CVAA Phenylarsine oxide LOD 500 ppt Short window for detection. Lack of validation in human samples. 

It is noteworthy that, unlike the previously described induces of PTPC opening, GD3 is able to exert its effect on mitochondria even in the presence of submicromolar calcium concentration (Kristal and Brown, 1999a), a property shared only by the most potent PT inducers, such as the thiol cross-linking agent phenylarsine oxide and by the peptide mastoparan. This low calcium requirement is important because intracellular calcium concentration during CD95-mediated apoptosis was not described to rise above 0.4 pM (Oshimi and Miyazaki, 1995). 

Phenylarsine oxide (20 [rM 30 minutes) is used as an inhibitor for receptor-mediated (clathrin-mediated) endocytosis (48). 

Water/waste water Measure initial temperature and pH and protect sample from light throughout the procedure. Phenylarsine oxide is used as Amperometric titration 0.5 mg/L No data APHA 1998 (Method 2350-C) (Method 4500-CL02-C) (Method 4500-CL02-E)... 

For APHA Methods 2350-C and 4500-CL02-E, amperometric analyzers are used to measure chlorine dioxide in water. Amperometric analyzers measure the current that is necessary to maintain a constant concentration of titrant as chlorine dioxide reduces the titrant (e.g., phenylarsine oxide). This method is limited by interference from compounds that might react with the titrant (e.g., chlorine and chloroamine) (APHA 1998). 

Chlorine gas may be identified readdy by its distinctive color and odor. Its odor is perceptible at 3 ppm concentration in air. Chlorine may be measured in water at low ppm by various titrimetry or colorimetric techniques (APHA, AWWA and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington DC American Pubhc Health Association). In iodometric titrations aqueous samples are acidified with acetic acid followed by addition of potassium iodide. Dissolved chlorine liberates iodine which is titrated with a standard solution of sodium thiosulfate using starch indicator. At the endpoint of titration, the blue color of the starch solution disappears. Alternatively, a standardized solution of a reducing agent, such as thiosulfate or phenylarsine oxide, is added in excess to chlorinated water and the unreacted reductant is then back titrated against a standard solution of iodine or potassium iodate. In amperometric titration, which has a lower detection limit, the free chlorine is titrated against phenyl arsine oxide at a pH between 6.5 and 7.5. 

The total free chlorine in wastewaters as measured by colorimetric techniques constitutes both the dissolved molecular chlorine, hypochlorite ion, OCl, and hypochlorous acid. An equilibrium exists between these species, the concentrations of which depend on the temperature and pH of the waste-water. Concentration of the hypochlorous acid may be estimated from the K value or from the ratio (33% of the measured concentration of free chlorine). The free chlorine may be measured by amperometric titration after the addition of a phosphate buffer solution to produce a pH between 6.5 and 7.5. The sample is titrated against a standard solution of phenylarsine oxide. Alternatively, the syringaldazine (3,5-dimethoxy-4-hydroxybenzaldazine) colorimetric test may be performed. This color-forming reagent in 2-propanol yields a colored product with free chlorine, the absorbance of which may be... 

Lenartowicz, E., Bernardi, P., and Azzone, G. F., 1991, Phenylarsine oxide induces the cyclosporin A-sensitive membrane permeability transition in rat liver mitochondria, J. Bioenerg. Biomembr. 23, pp. 679-688... 

Redox titrations find numerous applications in environmental analysis. Iodo-metric titration involving the reaction of iodine with a reducing agent such as thiosulfate or phenylarsine oxide of known strength is a typical example of a redox titration. This method is discussed separately in the next section. Another example of redox titration is the determination of sulfite, (S032-) using ferric ammonium sulfate, [NH4Fe(S04)2]. 

Periodic acid or periodate solutions are standardized by adding an excess of potassium iodide and then titrating the liberated iodine against a standard solution of sodium thiosulfate, phenylarsine oxide, or sodium arsenite. One mole of periodate liberates an equimolar amount of iodine as per the following reaction ... 

Redox titrations are often performed for metal analysis. Metals in their lower oxidation states are common reducing agents. This includes Fe2+, Sn2+, Mo3+, W3+, Ti3+, Co2+, U4+, and V02+. Sodium thiosulfate, (Na2S203) is one of the most widely used reductants in iodometric titrations. Other reducing agents include sodium arsenite and phenylarsine oxide. Iodometric titration is discussed separately in the next section. 

Phenylarsine oxide, C6H5As = O, is as effective as sodium thiosulfate in reducing iodine. It is more stable than thiosulfate. An advantage is that it is stable even in dilute solution. This substance is, however, highly toxic and is a suspected carcinogen. Because of its toxicity, its application is limited. One such application is in the amperometric titration of residual chlorine. The oxidation-reduction reaction of PAO is similar to thiosulfate. Its equivalent weight in iodine reaction is 168. 

Dissolve 1 g of KI in the above solution. Add 10 mL of 1 4 H2S04. Allow the solution to stand in the dark for 5 min. Titrate this solution with standardized sodium thiosulfate or phenylarsine oxide solution, using starch indicator. Add the indicator when the solution becomes pale straw following the addition of Na2S203 or PAO. At the end point, the blue color disappears. Disregard any reappearance of blue color. Run a distilled water blank. 

The excess iodine (unreacted surplus iodine) is back titrated with standard sodium thiosulfate solution using starch indicator. Phenylarsine oxide may be used as a titrant instead of sodium thiosulfate. 

Phenylarsine oxide may also be used as the reducing agent in the titration, instead of sodium thiosulfate. 

Preparation and standardization of sodium thiosulfate/phenylarsine oxide solution 0.025 M dissolve 6.205 g sodium thiosulfate (Na C 5 H20) or 4.200 g phenylarsine oxide (C6H5 As = 0) [PAO] in distilled water. Add 0.5 g NaOH solid and dilute to 1 L. Standardize against potassium bi-iodate (potassium hydrogen iodate) solution as described below. 

Sims, C., and Harvey, R. D. 2004. Redox modulation of basal and beta-adrenergically stimulated cardiac L-type Ca2+ channel activity by phenylarsine oxide. Br. J. Pharmacol. 142 797-807. 

Clathrin-mediated endocytosis can be blocked by several pharmacologic inhibitors, including the antipsychotic drug chlorpromazine (Thorazine), the natural product ikarugamycin, and the antiviral drug amantadine. The metabolic poisons phenylarsine oxide and sodium azide also block CMF but additionally inhibit protein synthesis. Culture of cells under conditions that deplete potassium or calcium, treatment of cells with hypertonic sucrose, or acidification of the cytoplasm by addition of... 

Although ethylmethylphenylphosphine oxide was the first tetrahedral phosphorus compound to be resolved , only negative results were obtained when attempts were made to resolve methyl(a-naphthyl)phenylarsine oxide (142) by protonation and separation of (-i-)-a-bromocamphor-jc-sulphonate salts, or (c>-carboxyphenyl)methylphenyl-arsine oxide (143) or its anhydride 144 after protonation and use of (—)-brucine or (-l-)-morphine . The reversible combination of a tertiary arsine oxide with water was recognized at the outset and it is this property that is responsible for the racemization - ... 

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