Mechanistic studies in strong acids. 15. 4-[(3,4-Dimethoxyphenyl)azo]pyridine: two different pathways in the acid hydrolysis of the two methoxy groups

Protonation Sites of Indoles and Benzoylindoles

“…Experimental and theoretical aspects of this issue have been treated extensively. [20,27,28,[39][40][41][42][43] b) The Vector Analysis Method Medium effects have been treated successfully by characteristic vector analysis (CVA) in the protonation of amides, [28c,42d] hydroxamic acids, [27,28a] pyrimidines, [28d] hydrazones [44] and ketones. [45] This method reduces the experimentally determined absorbance readings into the minimum number of independent components capable of reproducing the spectral curves, from which reliable ionization ratios can be deduced.…”

“…The Cox-Yates and vector analysis methods have been shown to be most efficient and are widely used. [26][27][28]39] a) The Cox-Yates Method This method, developed by Cox [31,40] from an earlier approach, [41] involves introduction of the excess acidity function (or medium parameter) X [Equation (9)] and enables the analysis of a large number of spectral curves over a wide wavelength range, yielding consistent and reliable results. Thermodynamic pK SH + values can only be determined from extrapolation to infinite dilution of the data pairs measured in aqueous solutions, see Equation (10).…”

Acid–base behaviour of organopalladium complexes [Pd(CNN)R]BF4

“…Experimental and theoretical aspects of this issue have been extensively treated. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Evaluation of the X function in 10% ethanol-water at temperatures different from 25 1C, required use of the X function in water 22,23 and the relationship X T = X 298.15 (298.15/T), 24 but the results provided (not shown) agreed only poorly with those from other acidity functions. Under I in Table 1 are listed the pK SH 2+ values provided in 10% ethanol-water at 25 1C; due to the limited capability of the program used, the results may vary with the particular range of wavelengths, hence the constant value was averaged.…”

“…The Cox-Yates method. This method, developed by Cox et al 16 from an earlier approach, 17,18 involves introduction of the excess acidity function X (or medium parameter); X represents the difference between the observed acidity and that of the system if it behaves ideally, 19 and is based on the free energy relationship:…”

The decomposition of aliphatic N-nitro amines in aqueous sulfuric acid. Bisulfate as a nucleophile

“…The results are analyzed using the excess acidity method (l), which has been widely applied to organic reactions in sulfuric acid in recent years, most recently to aromatic hydrogen exchange (12), phenylazo ether cleavage (13), imidazole cyclizations (14), and the hydrations of fluorinated alkyl vinyl ethers (15).…”