17333-85-6Relevant articles and documents
Spectroscopic and thermal properties of newly mixed azocalix[4]arene ester derivatives
?zkinali, Sevil
, p. 81 - 89 (2014/05/06)
The mono-, di-, tri-, and tetra-acryloyl esters of p-chloroazocalix[4]arene which include the first examples of mixed azo ester dyes were synthesized by reacting acryloyl chloride with sodium salts of p-chloroazocalix[4]arene in tetrahydrofuran with inert atmosphere. Diazonium salt of p-chloroaniline was synthesized by using n-amlynitrite and coupled with calix[4]arene in anhydrous condition. This is the diazo coupling reactions used for the first time for synthesized azocalix[4]arene. The characterization of synthesized compounds by spectroscopic methods revealed that azocalix[4]arenes adopt a cone conformation if they contain at least one free phenolic group. The structures of these compounds have been characterized by infrared (IR), ultraviolet-visible (UV-VIS), proton nuclear magnetic resonance (1H NMR) and carbon nuclear magnetic resonance (13C NMR). Differential thermal analysis (DTA), thermogravimetry (TG) and derivative thermogravimetry (DTG) were used to determine the thermal behaviors of the compounds.
Substituent effects on the thermal cis-to-trans isomerization of 1,3-diphenyltriazenes in aqueous solution
Chen, Nan,Barra, Monica,Lee, Ivan,Chahal, Navjot
, p. 2271 - 2277 (2007/10/03)
The thermal cis-to-trans isomerization of some symmetrically p,p′-disubstituted 1,3-diphenyltriazenes has been studied by means of laser-flash photolysis techniques. The geometric isomerization is catalyzed by general acids and general bases as a result of acid/base-promoted 1,3-prototropic rearrangements. Acid catalysis becomes more prominent as the electron-donating character of the para substituent increases, while base catalysis becomes more important as the electron-withdrawing character of the para substituent increases. In addition, the rate ascribed to the interconversion of neutral cis rotamers through hindered rotation around the nitrogen-nitrogen single bond is found to decrease as the electron-withdrawing character of the para substituent increases. Rates of interconversion of neutral cis rotamers are also found to decrease with decreasing solvent polarity, which is indicative of the involvement of a polar transition state. On the other hand, kinetic investigations of the acid-catalyzed decomposition of target triazenes are consistent with an A1 mechanism.
Mechanism of the Oxidation of NADH by Quinones. Energetics of One-Electron and Hydride Routes
Carlson, Brian W.,Miller, Larry L.
, p. 479 - 485 (2007/10/02)
The kinetics of NADH oxidation by 7 o-benzoquinones and 14 p-benzoquinones were studied by using buffered aqueous solutions and UV/vis spectroscopy.For each quinone the rate law was first order in NADH and first order in quinone.The rate constants varied from 0.0745 to 9220 M-1s-1.Variation of the pH from 6 to 8 gave no change in rate.The use of 4-D and 4,4-D2NADH revealed kinetic isotope effects.The dideutero data gave kH/kD in the range 1.6-3.1 for p-quinones and 4.2 for 3,5-di-tert-butyl-o-quinone.When p-quinones were used, the log k was a linear function of Eo for the quinone/hydroquinone monoanion (Q/QH(1-)) couple with a slope of 16.9 V-1. o-Quinones reacted about 100 times more rapidly, but the same linear relationship with a slope of 16.4 V-1 was observed.Comparisons to data for one-electron-transfer reactions indicate that such mechanisms are not involved.A hydride-transfer mechanism accommodates all the data, and rate-limiting hydrogen atom transfer followed by electron transfer cannot be ruled out.