Stibonous acid

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

Stibonic and Stibinic Acids. The stibonic acids, RSbO(OH)2, and stibinic acids, R2SbO(OH), are quite different in stmcture from their phosphoms and arsenic analogues. The stibonic and stibinic acids are polymeric compounds of unknown stmcture and are very weak acids. lUPAC classifies them as oxide hydroxides rather than as acids. Thus CgH3SbO(OH)2 is named phenyl antimony dihydroxide oxide [535-46-6], the Chemical Abstracts n.2ixn.e is dihydroxyphenylstibine oxide [535-46-6], CgH OgSb. 

Aromatic stibonic acids are readily prepared by the dia2o reaction ... 

Stevia, 12 42-43 Stevia plant, 24 239 Stevioside, 24 239-240 Stibabenzene, 3 72 Stibaboranes, 4 204 Stibiconite, 3 41 Stibine, 3 57-58 Stibine oxides, 3 73-74 Stibnite, 3 41 Stibonic acids, 3 72 Stichtite, 6 471t... 

Reduction with sodium dithionite has been used for conversion of aryl arsonic and aryl stibonic acids to arsenobenzenes [260] and stibinobenzenes in good yields [261]. 

Compounds (p-YC6H4)2SbBr2(acac) (Y = N02, Cl, H, CI[3, CHsO) were prepared from p-YC6H4SbO(OH)2 11, 18h) and p-YC6H4SbCl3(acac) (Y = N()2, H, CH3) were obtained from corresponding stibonic acid (18a, b). HMPA = hexamethylphosphoric triamide DMSO = dimethyl sulfoxide PyO = pyridine iV-oxide 4-CHjPyO = y-picoline JV-oxide TPPO = triphenylphosphine oxide. 

Inspite of these investigations, the structure of polymeric stibonic acids themselves can not be yet considered to be established with definiteness. 

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