Sodium arsenite, reduction

Methylene bromide (CHjBfj) and methylene iodide (CHjIj) are easily prepared by the reduction of bromoform or iodoform respectively with sodium arsenite in alkaline solution ... 

Azoxybenzene is readily prepared by reduction of nitrobenzene in an alkaline medium with dextrose or sodium arsenite ... 

Where X is Br or Q, the free acids may be obtained by acidification of the alkaline solution, but where X is I, the acids must be isolated as salts to avoid reduction of the arsonic acids by HI. Rather than using alkyl haUdes, alkyl or dialkyl sulfates or alkyl arenesulfonates can be used. Primary alkyl haUdes react rapidly and smoothly, secondary haUdes react only slowly, whereas tertiary haUdes do not give arsonic acids. AHyl haUdes undergo the Meyer reaction, but vinyl hahdes do not. Substituted alkyl haUdes can be used eg, ethylene chlorohydrin gives 2-hydroxyethylarsonic acid [65423-87-2], C2H2ASO4. Arsinic acids, R2AsO(OH), are also readily prepared by substituting an alkaU metal arsonite, RAs(OM)2, for sodium arsenite ... 

Azoxy compounds can be obtained from nitro compounds with certain reducing agents, notably sodium arsenite, sodium ethoxide, NaTeH, NaBH4—PhTeTePh, and glucose. The most probable mechanism with most reagents is that one molecule of nitro compound is reduced to a nitroso compound and another to a hydroxylamine 119-42), and these combine (12-51). The combination step is rapid compared to the reduction process. Nitroso compounds can be reduced to azoxy compounds with triethyl phosphite or triphenylphosphine or with an alkaline aqueous solution of an alcohol. ... 

Toluenesulfinic acid and its salts have been prepared by three general methods (1) The reduction of the sulfonyl chloride. The reagents which have been used for this arc sodium amalgam,1 zinc dust in alcohol or water,2 sodium sulfite,3 sodium sulfide,4 potassium hydrosulfide 5 (the thio acid being first formed) and sodium arsenite.6 (2) From toluene by the Friedel and Crafts reaction, using either sulfur dioxide and hydrogen chloride 7 or sulfuryl chloride.8 (3) From -toluidine by diazotization and... 

A special use of sodium arsenite (applied in aqueous alkaline solutions) is partial reduction of trigeminal halides to geminal halides [220] and reduction of aromatic nitro compounds to azoxy compounds [221]. 

Geminal dihalides undergo partial or total reduction. The latter can be achieved by catalytic hydrogenation over platinum oxide [512], palladium [512] or Raney nickel [63, 512], Both partial and total reduction can be accomplished with lithium aluminum hydride [513], with sodium bis(2-meth-oxyethoxy)aluminum hydride [514], with tributylstannane [503, 514], electro-lytically [515], with sodium in alcohol [516] and with chromous sulfate [193, 197]. For partial reduction only, sodium arsenite [220] or sodium sulfite [254] are used. 

Azoxybenzene was synthesized in 85% yield by reduction of nitrobenzene with sodium arsenite [221]. Nitrotoluenes and 2,5-dichloronitrobenzene were converted to the corresponding azoxy compounds by heating to 60-90° with hexoses (yields up to 74%) [316. Some ring-substituted nitrobenzenes were converted to azoxy compounds, some other to azo compounds by sodium bis 2-methoxyethoxy)aluminum hydride [575]. 

A detailed procedure for the reduction of nitrobenzene with sodium arsenite according to Eq. (41) has been published [46] (Eq. 41). 

The bimolecular reduction of aromatic nitro compounds, depending on reaction conditions, may produce azoxy compounds, azo compounds, hydrazo compounds (1,2-diarylhydrazines), benzidines, or amines. Whereas the reduction with zinc and sodium hydroxide leads to azo compounds, zinc and acetic acid/acetic anhydride produces azoxy compounds. Other reducing agents suggested are stannous chloride, magnesium with anhydrous methanol, a sodium-lead alloy in ethanol, thallium in ethanol, and sodium arsenite. 

The reduction of iodoform by means of sodium arsenite,6 described both by V. Auger and A. Gutmann, gave such successful results that the other methods were disregarded. The reaction is extremely simple and in the course of a few hours several pounds of pure methylene iodide may be prepared. 

The marine facultative anaerobe bacterium Serratia marinoruhm and the yeast Rhodotoruhi rubra both methylate arsenate ion to methylarsonate, but only the latter produces cacodylic acid (258). Human volunteers who ingested 500 fig doses of As as sodium arsenite, sodium methylarsonate, and sodium cacodylate excreted these compounds in their urine (259). Of these three, approximately 75% of the sodium arsenite is methylated, while 13% of methylarsonate is methylated. Rat liver subcellular fractions methylated sodium arsenate in vitro, providing the first direct evidence for possible mammalian methylation independent of symbiotic bacteria (260). Shariatpanahi el al. have reported kinetics studies on arsenic biotransformation by five species of bacteria (261). They found that the As(V)-As(IIl) reduction followed a pattern of two parallel first-order reactions, while the methylation reactions all followed first-order kinetics. Of the five species tested, only the Pseudomonas produced all four metabolites (arsenite, methylarsonate, cacodylate, trimethylarsine) (261). 

A variety of reducing agents have been used hut the usual ones are -sodium methoxide in MeOH or sodium arsenite. The azoxy compd results from the condensation of the nitroso and the hydroxylamine compds produced during the reduction. The nitroso and hy-droxyi amine compds can be prepd separately and condensed together to give the azoxy compd. Even when the nitroso and the hydroxylamine compds contain different substituted groups, with only one or two exceptions sym azoxy compds (R = R ) are formed, and not the unsym azoxy compd, as expected. Another method for prepg azoxy compds is by the oxidn of azo compds ... 

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. 

Additional reduction methods reported in the literature but seldom used include the use of sodium bisulphite sodium sulphide, sodium arsenite , titanous chloride tin-hydrochloric acid and sodium-ethanol . 

D) Reduction of Iodoform to Methylene Iodide. To 1 g of iodoform add 5 ml of sodium arsenite solution (made by dissolving 2.5 g of arsenic oxide and 5.5 ml of sodium hydroxide in 25 ml of water). The test tube is warmed for 5 minutes at 60-65° in a water bath and the mixture diluted with water. The oily drops which separate are methylene iodide. Look up the density and refractive index of the iodide. 

Drinking water, sea water Reduction of sample with SnCI2 in H2S04 oxidation with KMn04 addition of Cd(IV), sodium arsenite, iodide, and H2S04 to thermometric cell inject sample Kinetic thermometry 2 g/L No data Mateo et al. 1988... 

The fact that the Simmons-Smith reaction is regio- and stereoselective enabled the preparation of tritium containing cyclopropane derivatives useful for biological studies. The tritiated diiodomethane was prepared by reduction of iodoform with sodium arsenite in the presence of tritiated water. The carbene generated from tritiodiiodomethane and triisobutylaluminum in chloroform underwent regioselective addition to the unhindered double bond in perillyl alcohol (34). ... 

Benzo[c]cinnolines are often found as by-products of diazotization reactions of 2,2 -diaminobiphenyls. Reduction of the bisdiazonium salts from the diamines with sodium arsenite" or hypophosphorous acid ° increases the amounts obtained, although yields are usually low e.g., 10 is formed from 9 in 22% yield by this method. Alternative ionic and homolytic" mechanisms have been suggested for the process, each involving elimination of one of the diazonium groups as nitrogen. However, recent work by Rees and his co-workers has shown that at least part of the benzo[c]cinnolines... 

---