Arsinic acids arsine oxides

Similar reactions on alkyl or aryl arsonites yield the arsinic acids R2AsO(OH) and Ar2AsO(OH). Arsine oxides are made by alkaline hydrolysis of R3ASX2 (or Ar3AsX2> or by oxidation of a tertiary arsine with KMn04, H2O2 or I2. 

Calcium-binding proteins, 6, 564, 572, 596 intestinal, 6, 576 structure, 6, 573 Calcium carbonate calcium deposition as, 6, 597 Calcium complexes acetylacetone, 2, 372 amides, 2,164 amino acids, 3, 33 arsine oxides, 3, 9 biology, 6, 549 bipyridyl, 3, 13 crown ethers, 3, 39 dimethylphthalate, 3, 16 enzyme stabilization, 6, 549 hydrates, 3, 7 ionophores, 3, 66 malonic acid, 2, 444 peptides, 3, 33 phosphines, 3, 9 phthalocyanines, 2,863 porphyrins, 2, 820 proteins, 2, 770 pyridine oxide, 3,9 Schiff bases, 3, 29 urea, 3, 9... 

The compound is digested with nitric acid and the solution is analyzed for antimony by AA or ICP spectrophotometry (see Antimony). To determine the chlorine content a measured amount of substance is heated at 300°C and the liberated CI2 is passed into an acidic solution of KI and analyzed by iodomet-ric titration using a standard solution of sodium thiosulfate or phenyl arsine oxide and starch indicator. 

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. 

Iodine in aqueous solution may be measured quantitatively by acidifying the solution, diluting it, and titrating against a standard solution of sodium thiosulfate, sodium arsenite or phenyl arsine oxide using starch indicator. The blue color of the starch decolorizes at the end point. The indicator must be added towards the end of titration when the color of the solution turns pale yellow. Prior to titration, iodine in the dilute acidic solution is oxidized to iodate by adding bromine water or potassium permanganate solution. Excess potassium iodide is then added. The liberated iodine is then titrated as above. 

The preparation and properties of 2-substituted isoarsindolines (28) have been examined in some detail. They are prepared from o-xylylene dibromide (32) by the reactions shown in Scheme 8 (50JCS1917). Isoarsindolines have many of the properties of stable tertiary arsines and form arsine oxides, methopicrates and methiodides. With concentrated nitric acid the intermediate arsine oxide is polar enough to react further to give the water soluble hydroxynitrate (33). With boiling hydriodic acid, 2-iodoisoarsindoline (34) is formed. This... 

RAs(OH)2 for arsonic acids and R2A8—OH for arsinic adds. The neutral arsine oxides, R3As—>0, may be considered as derivatives in which all the hydroxyl groups have been replaced by organic residues. 

Arsinic acids and arsine oxides may be prepared by extensions of the t Bart synthesis. Thus, diphenylardnic acid is obtained from benzene- diazonium chloride and disodium phenylarsenite. 

SYNS ARSINE OXIDE, (m-CHLOROPHENYL)-HYDROXY(P-HYDROXYPHENETHYL)- 2-PHENYL-2-HYDROXYETHYL, m-CHLOROPHENYL ARSINIC ACID... 

SYNS ARSINE OXIDE, DIBUTYLHYDROXY- ARSINIC ACID, DIBUTYL-(9CI)... 

SYNS ARSENIC ACID, METHYLPHENYL-(9CI) ARSINE OXIDE, HYDROXYMETHTXPHENYL- METHYLPHENYLARSINIC ACID METHYL-PHENYLARSONIC ACID... 

Oxidation of these compounds by dilute nitric acid yields arsinic acids, whilst oxidation by air results in arsenoxides. The compounds react with alkyl iodides, the resulting products being fully dealt with in the following pages. 

Tertiary arsine oxides containing nitro groups are conveniently isolated by dissohnng the arsine in mixed acid and pouring the mixture into a large bulk of water. In this case the nitro group enters the ring in the meta position to the arsenic. 

The (-h )-enantiomer of the arsino-acetic acid 51 was isolated with use of ( —)-a-methylbenzylamine as resolving agent (Table 2) . The racemic arsine was prepared by permanganate oxidation of allylethylphenylarsine, followed by SO2/HCI reduction of the intermediate arsine oxide. 

Sodium ethylphenylarsenide with carbon dioxide yields crystalline ethylphenylarsino-formic acid (52) after treatment with dilute sulphuric acid . The arsinoformic acid was resolved with (—)-quinine. The less-soluble diastereomer, after three recrystallizations from chloroform, was decomposed with dilute sulphuric acid into (— )-52, which required purification by extraction into benzene to separate it from arsine oxide (Table 2). 

Cyclization of arsinic acid 40 gives arsine oxide 41 by use of phosphoric acid (equation... 

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