Arsenite esters

This was reviewed in CHEC-II(1996) <1996CHEC-II(9)971>. There have been no further studies except deprotonation of the cyclic arsenite esters 40-42 reported in Section 14.18.3.2. 

By analogy to simple carboxylic acid derivatives such as esters [cf. J. F. Liebman and J. S. Chickos, Struct. Chem., 1, 501 (1990)], it is not unreasonable to assume that the vaporization substituent parameter for arsenite esters, b(AsO ), should approximately equal b (As) + 3b (O). From the somewhat more refined observation that simple summation generally overestimates the b of the composite group by some 5kJmol", we conclude that b AsOf) = b (As) + 3b (O) —5 and so b (As) should equal ca 12kJmol"L Indeed, this value reproduces to within IkJmoP the experimentally measured enthalpies of vaporization of both trimethyl and triethylarsine. 

The esterification of AS2O3 with alcohols is a very straightforward method for the synthesis of heterocyclic arsenite esters, i.e. (32) - (33) (Equation (5)). However, a more general approach to the synthesis of 1,3,2-dioxarsinanes is the reaction of 1,3-diols with AsClj or with As(NMc2)3, for example (34) and (35) (Scheme 3) (Section 6.26.5.l.l.i). 

The reaction of R-C(CH20H)j with As(NMc2)3 by cleavage of the As—N bond leads to the bicyclic arsenite esters (231 R = CH2OH, Me) in yields of 75-90% <76ZN(B)307>. c -Cyclohexane-... 

The sodium arsenite product is an article of commerce, although of low value. Petrov et al. (this volume) describe the analogous reaction with sodium alkoxides, which forms trialkyl arsenite esters instead of sodium arsenite. 

AsXs and SbXs react with alcohols (especially in the presence of bases) and with sodium alkoxide to give arsenite and antimonite esters, M(0R)3 (cf. phosphorus, (p. 515) ... 

C. Spontaneous Formation of Esters of Arsenate The Biochemistry of Arsenite... 

Cresylic Acid 13464-37-4 Sodium Arsenite 141-78-6 Acetic Acid Ethyl Ester... 

Catalysts having a very acid nature such as metaphosphoric acid, arsenious acid, boric acid, or salts of these acids have been proposed. The addition of copper as such or as the formate serves to promote the reaction.190 Reaction chambers extremely resistant to corrosion must be tised. Catalysts such as zinc arsenite. or zinc or chromium metaphosphatc having a highly acidic nature are claimed to be effective in the formation of organic acids from carbon monoxide and alcohols at temperatures of about 300° C. and a pressure of 200 atmospheres. Even with such acidic catalysts considerable quantities of esters are stated to be formed.101... 

Oxoalkylarsonic acids, exemplifled by arsonoacetaldehyde and 3-arsonopyruvate, are only moderately stable they release arsenate by hydrolysis, rather than arsenite by elimination. They are presumably hydrolyzed by the mechanism of Fig. 7, but they do not need the added electron attraction of forming the imine E—NH =CR—CH2— AsOgHg 0=CR—CH2—ASO3H2 is fairly easily attacked by water. 2-Oxoalkylphosphonic acids can be hydrolyzed in this way (119), as in the enzyme-catalyzed hydrolysis of phosphonoacetaldehyde (73, 69-71), but with much more difficulty. The lability of 2-oxoalkylarsonic acids presumably reflects the ease with which water can more easily enter the coordination shell of arsenic than that of phosphorus, because of the larger size of the atom, i.e., the same feature expressed in the lability of esters and anhydrides of arsenate. 

Although arsinoacetic acid is readily produced from chloroacetic acid and an excess of sodium arsenite, the analogous reaction does not take place with sodium phosphite. Sodium salts of phosphorous and chloroalkyl acids when brought into contact react with a partial conversion of the phosplioms into the quinquevalent state, and, apparently, the production of an unstable ester-like derivative of glycolhc and phosphorous acids which cannot be isolated. Methyl iodide and sodium phosphite yield the readily hydrolysed methyl phosphite unaccompanied by methylphosphimc acid. 

The formaldehyde formed in a periodate reaction is determined gravimet-rically with Dimedon, or colorimetrically with chromotropic acid, after the excess oxidant is destroyed with ethylene glycol, stannous chloride, sodium arsenite, or sodium bisulfite 221), The formic acid is generally titrated directly. Titration to pH 6.0 will measure all the formic acid present. Titration to higher alkalinities will usually measure any formic acid bound as an ester 222) but also other acidic products the end-point may be indefinite. Sucrose will give 80 to 90 % of the theoretical formic acid, and maltose and lactose similarly low values. Both formaldehyde and formic acid are attacked only extremely slowly by periodate, but light apparently accelerates an oxidation to carbon dioxide and water 223),... 

Threo- and erj/f/ ro-isomers of vicinal dihydroxy esters can be separated on thin layers of silica gel impregnated with boric acid (10 % w/w) as a complexing agent, with hexane-diethyl ether (60 40, v/v) as the developing solvent (the fhreo-isomer migrates more rapidly) the compounds cannot be separated on silica gel alone [618], Sodium arsenite-impregnated layers give even more remarkable separations of isomeric polyhydroxy fatty acids. 

Methylation of Inorganic oxyarsenic anions occurs in organisms ranging from microbial to mammalian methylated and products include arsenocholine, arsenobetaine, dimethylarsinic acid, and methylarsonic acid arsenite methyltransferase and monomethylarsonic acid methyltransferase use S-adenosylmethionine for the methyl donor Boron biochemistry essentially that of boric acid, which forms ester complexes with hydroxyl groups, preferably those adjacent and cis, in organic compounds. Five naturally occurring boron esters (all antibiotics) synthesized by various bacteria have been characterized Exists as Br Ion in vivo, binds to proteins and amino acids... 

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