3044-15-3Relevant articles and documents
Rate-limiting formation of diazonium ions in the aqueous decomposition of primary alkanediazoates
Ho, Jian,Fishbein, James C.
, p. 6611 - 6621 (1994)
Rate constants, k0, for the buffer-independent decomposition of four primary (E)-alkanediazoates and one primary (Z)-alkanediazoate in aqueous media at 25 °C, ionic strength 1 M (NaClO4) are reported. Between pH 4 and 12 the plot of log k0 against pH is biphasic with a hydrogen ion-dependent reaction at the high-pH end changing to a pH-independent region at lower pH. The change in absorbance at 235 nm of the relatively stable (E)-trifluoroethanediazoate as a function of pH gives a good fit to a simple titration curve for a monofunctional acid with pKa = 7.00 ± 0.04 that is in good agreement with the kinetic pKa determined from the pH-rate profile between pH 4 and 12. The plot of log k1, the pH-independent rate constant, against σ* for the primary (E)-alkanediazoates, and (E)-methane- and (E)-2-butanediazoates previously reported, yields a common line with a slope ρ* = -4.4. Of the 1-butanol formed from the decomposition of (E)-1-butanediazoate in D2O at pHobs = 10.50,6% contains deuterium, while, of the 1-butanol formed in the presence of 1 M NaOD in D2O, 25% contains deuterium. A total of 96% of the iodotrifluoroethane formed upon decomposition of (E)-trifluoroethanediazoate in a D2O solution that is 1 M in NaI contains at least a single deuterium atom. These data combined with small negative values of ΔS# normal solvent deuterium isotope effects, and the decreases in k1 of between 500- and 1000-fold on change of solvent to ethanol are consistent with a mechanism that involves the rate-limiting unassisted heterolytic bond fission of the diazoic acid to yield the diazonium ion. The decomposition of [16O]-(E)-1-butanediazoate in water containing 47 ± 2% 18O yields 1-butanol of which 49 ± 2% contains 18O. This observation, in combination with the observed pH-dependent deuterium incorporation into 1 -butanol during decomposition of (E)-1-butanediazoate, above, indicates that the 1-butanediazonium ion is a diffusionally equilibrated intermediate. The rate constant for the pH-independent decomposition of the (Z)-trifluoroethanediazoate is 2600 times greater than that for the corresponding (E) isomer. The decomposition of the (Z)-trifluoroethanediazoate, but not its (E) isomer, is catalyzed by buffer acids, and the catalysis by carboxylic acids is characterized by a Bronsted plot with a slope a = 0.41. Catalysis by methoxylammonium ion is comparatively weak, the rate constant falling a log unit below the aforementioned Bronsted line. The solvent deuterium isotope effect for formic acid catalysis is kHA/kDA = 3.1 ± 0.2. It is concluded that the mechanism for general acid catalysis of the decomposition of the (Z)-diazoic acid entails proton transfer to oxygen that is concerted with N-O bond heterolysis to yield the diazonium ion.
3-[1-(2-Benzoxazolyl)hydrazino]propanenitrile derivatives: Inhibitors of immune complex induced inflammation
Haviv,Ratajczyk,DeNet,Kerdesky,Walters,Schmidt,Holms,Young,Carter
, p. 1719 - 1728 (2007/10/02)
3-[1-(2-Benzoxazolyl)hydrazino]propanenitrile derivatives were evaluated in the dermal and pleural reverse passive Arthus reactions in the rat. In the pleural test these compounds were effective in reducing exudate volume and accumulation of white blood cells. This pattern of activity was similar to that of hydrocortisone and different from that of indomethacin. The structural requirements for inhibiting the Arthus reactions were studied by systematic chemical modification of 1. These structure-activity relationship studies revealed that nitrogen 1' of the hydrazino group is essential for activity and must be electron rich, whereas chemical modifications of other sites of 1 had only a modest effect on activity.
