108-96-3Relevant articles and documents
Chemistry of ketoacetals: II. β,β′-Ketodiacetal and β,β′-hydroxydiacetals in reactions with amminia and amines
Kharitonova,Panin,Belova
, p. 1113 - 1115 (2005)
β,β′-Ketodiacetal and β,β′-hydroxydiacetals react with ammonium acetate in acetic acid to afford substituted pyridine, and with aromatic amines in the presence of hydrochloric acid form substituted pentamethine salts. 2005 Pleiades Publishing, Inc.
-
Bunton et al.
, p. 3267,3272,3275 (1974)
-
Equilibration of N-(2-cyanoethyl)pyridinium cations with substituted pyridines and acrylonitrile. A change in rate-determining step in an E1cb reaction
Bunting, John W.,Toth, Andrea,Heo, Christina K. M.,Moors, Rodney G.
, p. 8878 - 8885 (2007/10/02)
The rates of equilibration of N-(2-cyanoethyl)pyridinium cations (1) with the corresponding pyridines and acrylonitrile have been measured in aqueous solutions of ionic strength 0.1 at 25 °C. Second-order rate constants (kOH) have been obtained for the hydroxide ion catalyzed elimination reactions of 16 ring-substituted 1 having pyridine leaving groups of pKBH in the range 1.5-9.7. Bronsted plots of log kOH vs pKBH are "concave down" with two distinct linear regions having β1g = -0.30 (for pKBH 1g = -0.93 (for pKBH > 5.8). This observation is consistent with a change in rate-determining step within an E1cb reaction mechanism from rate-determining deprotonation of 1 (i.e., (E1cb)irrev) for pKBH rev) for pKBH > 5.8. This interpretation is supported by 1H NMR spectral observations in basic D2O, which show no incorporation of deuterium into the acrylonitrile product for pKBH BH > 5.8. Rates of nucleophilic attack of pyridines and pyridinone anions (pKBH > 6) upon acrylonitrile have also been measured. These display a linear Br?nsted plot of βnuc = 0.20. Combination of β1g and βnuc gives βeq = 0.13 for the Michael-type addition of pyridinium cations to acrylonitrile to produce 1. Although the rates of the addition of pyridines of pKBH nuc = 0.20 for pyridines of pKBH > 5.8 to rate-determining protonation of the carbanionic intermediate with βnuc = 0.83 for pyridine nucleophiles of pKBH irrev region but is extremely weak under the current experimental conditions.
EFFECT OF THE POSITION OF THE NITROGEN ATOM IN HETERO- AND HOMOAROMATIC HYDROXY COMPOUNDS ON THE CONTENT OF THE HIGHLY POLAR TAUTOMER OF AN ORGANIC AMPHOLYTE IN WATER
Zaionts, V. I.,Korovitskaya, L. A.,Agrest, F. B.,Gutshabach, E. Sh.,Yachkula, S. S.
, p. 1153 - 1158 (2007/10/02)
In the transition from 3-hydroxypyridine to 3-aminophenol the content of the highly polar tautomer is reduced by 1E4 times, while in the transition from 4-hydroxypyridine to 4-aminophenol it is reduced by 1E5 times.In the series of aminophenols the transition from the 3- to the 4-isomer leads to an increase of an order of magnitude in the content of the highly polar tautomer.The results from calculations of the content of the highly polar tautomer in the 3- and 4-aminophenol systems by a method where the acid-base constants of the systems and model compounds were used show that it is large enough at the isoelectric point (1E-3 and 1E-4 mole percent respectively) to be taken into account during discussion of the characteristics of these systems.The content of the highly polar tautomer is determined not only by the acidity of the hydroxy group in the molecule of the low-polarity tautomer and by the basicity of the endo- or exocyclic nitrogen atom in it but also by the stability of the molecule of highly polar tautomer.The latter, in turn, depends on the possibility of conjugation in its molecule.
