- Oxidation of diols by cetyltrimethylammonium dichromate
-
The oxidation kinetics of some diols have been investigated using cetyltrimethylammonium dichromate as the oxidant in dichloromethane in the presence of acetic acid and a cationic surfactant. A tentative mechanism has been proposed on the basis of (i) observed rate constant dependencies on the reactants, (ii) high negative entropy change and (iii) the kobs dependencies on surfactant concentration.
- Patel, Sabita,Sung, Dae Dong,Mishra
-
scheme or table
p. 1218 - 1221
(2009/03/11)
-
- Synthesis and aqueous chemistry of α-acetoxy-N-nitrosomorpholine: Reactive intermediates and products
-
α-Acetoxy-N-nitrosomorpholine (7) has been synthesized starting by the anodic oxidation of N-acetylmorpholine in methanol. The 55% yield of N-nitrosomorpholinic acid, after cyanide-for-methoxy group exchange and hydrolysis, is an improvement of ~10-fold over our original 10-step method, and this is readily converted to 7. A study of the kinetics of decomposition of 7 in aqueous media at 25 °C and 1 M ionic strength was conducted over the pH range from 1 to 12. The reaction exhibited good first-order kinetics at all values of pH, and a plot of the log of k0, the buffer-independent rate constant for decomposition, against pH indicated that a pH-independent reaction dominates in the neutral pH region whereas acid- and base-catalyzed reactions dominate in the low and high pH regions, respectively. Reaction at neutral pH in the presence of increasing concentrations of acetate ion results in a decrease in the value of kobsd, to an apparent limiting value consistent with a common-ion inhibition by the capture, and competing base-catalyzed hydration of, an N-nitrosiminium ion intermediate The 100-fold smaller reactivity of 7 at neutral pH compared with its carbon analogue, α-acetoxy-N-nitrosopiperidine, is also consistent with the electronic effects expected for such a reaction. The dinitrophenylhydrazones derived from pH-independent and acid-catalyzed reactions are identical in kind and quantity, within experimental error, to those observed in the decay of α-hydroxy-N-nitrosomorpholine. Decay of 7 in the presence of benzimidazole buffer results in the formation of 2-(2-(1H-benzo[d]imidazol-1-yl)ethoxy) acetaldehyde (12) and 2-(1H-benzo[d]imidazol-1-yl)ethanol (13). Independent synthesis and study of 12 indicates that it is stable at 80 °C in 0.1 M DCl, but it slowly decomposes to 13 in neutral and basic media in a reaction that is stimulated by primary and secondary amines, but not by tertiary amines and carbonate buffer. The benzimidazole trapping studies and those of the stability of 12 indicate the possibility that metabolic activation of N-nitrosomorpholine by hydroxylation α to the nitroso nitrogen can result in the deposition of a metastable ethoxyacetaldehyde adduct on the heteroatoms of DNA.
- Zink, Charles N.,Kim, Hyun-Joong,Fishbein, James C.
-
p. 202 - 209
(2007/10/03)
-
- Kinetics and mechanism of oxidation of diethylene glycol by dihydroxyditellutoargentate (III) in alkaline medium
-
The kinetics of oxidation of diethylene glycol (DG) by dihydroxyditelluratoargentate(III) (DDA) is studied spectrophotometrically between 298.2K and 313.2K in alkaline medium. A mechanism involving a one-step two-electron transfer has been proposed The activation parameters and the rate constants of the rate-determining step are calculated.
- Shan, Jin-Huan,Huo, Shu-Ying,Fei-Wang,Shen, Shi-Gang,Sun, Han-Wen
-
p. 674 - 675
(2007/10/03)
-
- AUTOOXIDATION OF DIETHYLENE GLYCOL.
-
The authors studied certain characteristics of the kinetics of accumulation of the products of autooxidation of diethylene glycol. Experiments show that both methylene groups in diethylene glycol exhibit reactivity during liquid-phase oxidation by atmospheric oxygen. During oxidation near the lower limit of the temperature range studied (90-130+ZZproducts whose formation involve cleavage of the C-O ether bond are formed at the higher rate, whereas at higher temperatures the products of conversion of the hydroxyl group predominate.
- Gordienok,Freidin,Proskurina
-
p. 1441 - 1445
(2007/10/02)
-
- Chemoselective Oxidation of the Primary Alcohol Function of Diols Catalyzed by Zirconocene Complexes
-
Zirconocene complexes, Cp2ZrH2 and Cp2Zr2, catalyze the Oppenauer-type oxidation of alcohol functions to the corresponding carbonyl compounds in the presence of an appropriate hydrogen acceptor such as benzophenone.In the oxidation of primary α,ω-diols and of diols containing two secondary alcohol functions, one of the alcohol functions is selectively oxidized to form hydroxy aldehydes and hydroxy ketones, respectively, in substantial yields.The chemoselective oxidation of the primary alcohol function can be achieved in the oxidation of diols containing both the primary and secondary alcohol functions.
- Nakano, Tatsuya,Terada, Takanobu,Ishii, Yasutaka,Ogawa, Masaya
-
p. 774 - 776
(2007/10/02)
-
- KINETICS OF THE HYDROLYSIS OF 1,4-DIOXENE IN AQUEOUS 1-PROPANOL
-
An experimental study showed anomalous behavior of the rate constants for the hydrolysis of 1,4-dioxene in aqueous 1-propanol in the region of relative molar water content from 0.32 to 0.74.A kinetic model was proposed for this reason describing the behavior of the rate constant which is related to the formation of an alcohol-water complex with enhanced nucleophilicity.
- Tsivunin, V. S.,Nasybullin, Sh. A.,Zaripova, V. G.,Ismagilov, R. M.,Zaripov, I. N.
-
p. 1379 - 1382
(2007/10/02)
-