Dithioformic acid

Moreover, potential reactions can be written for conversion of dithioformic acid to thioformic acid (Equation 3), and hence COS. 

From molecular weight determinations by cryoscopic methods, the esters of dithioformic acid appear to have a trimeric constitution, for example, (II.CS2Me)3, and it is suggested 3 that the molecule of the acid is similarly constituted and possesses a cyclic structure with alternating carbon and sulphur atoms. 

Unsubstituted phosphino- and arsino-dithioformic acids and their dithioformates have not yet been described. In addition, the monosubstituted primary alkyl and aryl compounds have not been investigated very well. Disubstituted phosphinodithioformates can be prepared easily. Because of the difference in basicity of Ph2PH and Et2PH they react with CS2 in different ways (reactions 14 and 15). By addition of metal ions to the resulting ethyl compound, one CS2 is split off.1 Only the potassium complexes have a second CS2 molecule bonded to the phosphorus atom. 

Tandem mass spectrometric experiments have been used to characterize both ionic and neutral parent dithiirane 3a in the gas phase <1999PCA5123>. Collision activation experiments have established the connectivity of dithioformic acid, dimercaptocarbene, and dithiirane 3a for the ion at miz 78 generated by electron ionization of ethyl carbamoylmethane-dithioate, 5-amino-l,3,4-thiadiazole-2-thiol, rhodanine, and 1,2-dithiacyclopentane, respectively. Theoretical calculation of the CH2S2 isomers and their radical cations at B3LYP/6-31G level have supported experimentally obtained data. 

In this case, other cyclization reagents, such as dithioformic acid, must be used. Although the application of dithioformic acid is superior to formic acid, the reaction may still be incomplete. 

The amino group of 4-amino-3-pyrazolin-5-ones reacts normally. Acylation occurs readily with a wide variety of acylating agents. Amides are formed by reaction with acid chlorides,50,533,984,1414,1473 acids618,984,1471 and esters in the presence of phosphorus pentoxide.1471 Thioformamides have been prepared by reaction with dithioformic acid and its salts.472,556,1374 Sulfonyl chlorides react to form sulfonamides.98,489,984,1249,1504 Chlorophosphates react with 4-amino-3-pyrazolin-5-ones to form phosphoramide derivatives.509,1498... 

The formamides 16 are intermediates. Formamide (Bredereck variant of the Traube synthesis [149]), formamidine, orthoformic ester, diethoxymethyl acetate, Vilsmeier reagent (fi om DMF and POCI3) and dithioformic acid are used as formic acid derivatives. 4,5-Diaminopyrimidines can be obtained from 4-aminopyrimidines 17 by nitrosation with HNO2 followed by reduction of the nitroso compounds 18 ... 

Neither stibino- not bismuthino-dithioformic acid, nor their dithioformates, are known. A triphenyltin complex of diphenylphosphinomonothioformate has been prepared by Schmidt et al. from COS and (97). ... 

Synthesis.— In an attempt to synthesize dithioformic acid by the action of dilute hydrochloric acid on potassium dithioformate (the product of the reaction between chloroform and potassium sulphide ), Gattow and Engler obtained a material consisting mainly of trimeric dithioformic acid. Recently, the same workers have also shown that the polymer of monothioformic acid in aqueous potassium hydroxide may undergo disproportionation, yielding equal amounts of formate and dithioformate anions. 

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