Pyridazine ionization constant

Pyridazine-3(2//)-thiones exist in the thione form (14), as is evident from an X-ray structure analysis of pyridazine-3(2//)-thione. 6-Mercaptopyridazine-3(2//)-thione is predominantly in the monothiolmonothione form (15) in aqueous solution and in the solid state, 6-hydroxypyridazine-3(2//)-thiones are in the hydroxythione form (16) and 6-aminopyridazine-3(2//)-thiones exist in the aminothione form (17) for further details see (73HC(28)755). Cinnoline-4(l//)-thiones and phthalazine-l(2//)-thione have been shown on the basis of UV data and ionization constants to exist in the thione forms. 

S-N rearrangement, 3, 36 ionization constants, 3, 4 oxidation, 3, 37 quatemization, 3, 17 Pyridazine-3 (2 H) - thiones analysis, 3, 2 tautomerism, 3, 5 Pyridazinium betaine, 3-oxido-photolysis, 3, 11 Pyridazinium betaine, 5-oxido-photolysis, 3, 11 Pyridazinium dicyanomethylide photolysis, 3, 12... 

The ionization constants of different mono- or polyalkylated pyridazines 4is g ow that the number and position of the alkyl groups affect the basicity of these compounds. Alkyl groups cause an increase in the basicity of pyridazine, due to inductive effects. Dipole moments have also been determined. The NMR spectrum of 3-methylpyridazine shows an ABX system in which —... 

Ionization constants of hydroxy- and mercaptopyridazines, ° of amino- and diaminopyridazines and their quaternization products,of methylsulfinylpyridazines," and of pyridazinium ylides have been recorded. The basicities of a series of pyridazines have been determined and correlated with substituent constants using the Hammett free-energy relationship. The magnetic susceptibility of pyridazine was measured, and the rate constant for the reaction of hydrogen atoms with pyridazine was determined. The experimental dipole moment, Kerr constant, and molar Cotton-Mouton constant, obtained at 298 K and 633 nm, are reported. The magnetic circular dichroism spectrum of pyridazine has been measured. ... 

Studies on the tautomerism of pyridazines with potential tautomeric groups have continued. On the basis of recorded ionization constants and UV spectra of 3,4,5-trimercaptopyridazine and its derivatives, it is concluded that the compound exists as 3,4-dimercaptopyridazine-5(2f/)-thione. Tautomerism of hydroxy- and mercaptopyridazines was investigated with the aid of the corresponding anhydro bases as reference compounds. They exist predominantly in the -one or -thione forms. Similarly, the 3-mercapto-pyridazine-6(l/f)-thione structure in aqueous solution has been redeter-... 

Homolytic substitution of pyridazines by N-acyl-pyrrolidines under Minisci conditions i.e. ammonium persulphate, and ferrous sulphate in sulphuric acid), has proved useful for the synthesis of azanicotine analogues, e.g. (198). Measurements of ionization constants and u.v. spectra of the N- and 5-methyl derivatives of 3,4,5-trimercaptopyridazine indicate that it exists as the N(2)-H tautomer (199).On the basis of X-ray and chemical data, the photo-isomers of pyridazine 1,2-dioxides, reported last year, have been re-formulated as 3a,6a-dihydroisoxazolo[5,4-ii]isoxazoles (200). 

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