Potential Mercapto Groups

In 1951, pyrid-4-thione was concluded from ultraviolet spectral data to exist predominantly as such in ethanolic solution,but no comparisons were made and this conclusion had to be considered as tentative. Pyrid-2-thione has been shown by X-ray crystallography to exist as hydrogen-bonded dimers (201) in the solid state, the posi- 

English and Australian investigators showed simultaneously that the pyrid-2- and -4-thione forms predominate in aqueous solution by factors of ca. 10 (see Table V) by comparative studies of these 

In 1939, the ultraviolet spectrum of 4-methylquinol-2-thione was reported to differ from that of the 2-alkylthio analog, and the former compound was concluded to exist in the thione form. However, other investigators were unable to reach any conclusions from ultraviolet and infrared spectral data concerning the tautomerism of quinol-2- and -4-thione. A definitive pK and ultraviolet spectral investigation by Albert and Barlin has recently established that the thione forms of quinol-2- and -4-thione and of isoquinol-1- and -3-thione (cf. 202) greatly predominate (Table V). The infrared 

3-Mercaptopyridine and 3-mercaptoquinoline have been shown to exist predominantly in the zwitterion form (e.g., 204) by ultraviolet spectral comparisons and pK measurements (cf. Table V). 

Quinolines Caerying a Mercapto Group on the Benzo Ring 

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Few pyrazolopyrimidines with potential mercapto groups have been investigated. l-Methylpyrazolo[3,4-d]pyrimidine-6-thione (308) exists in the... 

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