Ethanol ions, decomposition

Concentration of an ethanolic solution of dimethylglyoxime, cobalt(n) chloride and benzotriazole results in deposition of crystalline complex 68. The product is stable at room temperature however, it slowly decomposes upon heating. Thermal analysis reveals that the compound releases first the chlorine atom and 50% of the benzotriazole content to form a new complex that is stable to 225 °C. Probably in this new form, the benzotriazole moiety coordinates two cobalt ions simultaneously. Further heating to 350 °C removes the benzotriazolyl moieties completely <2003JPY699>. The first step of decomposition can be summarized as follows ... 

Hexabutyldistannane, which is an important reagent in many organic syntheses, can be prepared very conveniently by reducing bis(tributyltin) oxide with sodium borohydride in ethanol at room temperature. After 5 min, the only tin species present is tributyltin hydride, but in 2 h, its decomposition is catalyzed by the ethoxide ion that is formed to give the distannane in 83% yield.444 Hexaalkyldistannanes, R3SnSnR3 (R = Et, Pr, or Bu), are obtained in ca. 50% yield when the corresponding trialkyltin halides are treated with zinc powder in THF.445... 

The mechanism of the acid-catalyzed decomposition of 1-alkyltriazolines has been studied <93JOC2097>. The hydrolytic decomposition of these triazolines in aqueous buffers leads predominantly to 1-alkylaziridines with lesser amounts of 2-(alkylamino)ethanol, alkylamines, and acetaldehyde. The rate of hydrolysis of 1-alkyltriazolines is about twice as fast as that of the analogous acyclic 1,3,3-trialkyltriazenes and varies in the order t-butyl > isopropyl > ethyl > butyl > methyl > propyl > benzyl <92JOC6448>. The proposed mechanism, involving rate-limiting formation of a 2-(alkylamino)ethyldiazonium ion, is shown in Scheme 65. A theoretical study ab initio calculation) of the acid-induced decomposition of 4,5-dihydro-l,2,3-triazolines has also been reported <91JA7893>. 

Alcohols. In a reaction reminiscent of diazonium ion chemistry, 26 is reduced by ethanol to 13 (R = H). The ethanol is oxidized to acetaldehyde (72UP1). Like water, decomposition of 26 in f-butanol gives nitrogen in quantitative yield, but the other product is intractable. 

Macrae and Wright (96) demonstrated that visible light irradiation of xanthene dyes (eosin, erythrosin, rhodamine B, or RB) in ethanolic solutions of 4-(N,N-diethylamino)benzene-diazonium chloride (as the zinc chloride double salt) resulted in decomposition of the diazonium salt. Electron transfer from the dye excited state(s) to the diazonium salt was postulated and dye-diazonium salt ion pair formation in the ground state was shown to be important. Similar dyes and diazonium salts were claimed by Cerwonka (97) in a photopolymerization process in which vinyl monomers (vinylpyrrolidone, bis(acrylamide)) were crosslinked by visible light. Initiation occurs by the sequence of reactions in eqs. 40-42 ... 

The reaction chemistry of simple organic molecules in supercritical (SC) water can be described by heterolytic (ionic) mechanisms when the ion product 1 of the SC water exceeds 10" and by homolytic (free radical) mechanisms when <<10 1 . For example, in SC water with Kw>10-11 ethanol undergoes rapid dehydration to ethylene in the presence of dilute Arrhenius acids, such as 0.01M sulfuric acid and 1.0M acetic acid. Similarly, 1,3 dioxolane undergoes very rapid and selective hydration in SC water, producing ethylene glycol and formaldehyde without catalysts. In SC methanol the decomposition of 1,3 dioxolane yields 2 methoxyethanol, il lustrating the role of the solvent medium in the heterolytic reaction mechanism. Under conditions where K klO"11 the dehydration of ethanol to ethylene is not catalyzed by Arrhenius acids. Instead, the decomposition products include a variety of hydrocarbons and carbon oxides. 

As mentioned earlier, at 500° C and 34.5 MPa supercritical water has a small dielectric constant, a very low ion product, and behaves as a high temperature gas. These properties would be expected to minimize the role of heterolysis in the dehydration chemistry. As shown in Table 1, the conversion of ethanol to ethylene at 500° C is small, even in the presence of 0.01M sulfuric acid catalyst. The appearance of the byproducts CO, C02) CH i+ and C2H6 points to the onset of nonselective, free radical reactions in the decomposition chemistry, as would be expected in the high temperature gas phase thermolysis of ethanol. 

The decomposition of trichloroacetate ion in NMA has been found119 to follow pseudo-first order kinetics. The activation energy for the reaction was found to be intermediate between Verhoek s values for the activation energy of the decomposition in ethanol and in aniline245. ... 

Similar findings were obtained for the alkaline decomposition of triarylsulfonium halides with ethoxide ion in aqueous ethanol at 120 °C [71], The results indicate that the decomposition rate is decreased about 10 -fold by increasing the water content from 2.3 to 98.2 cmol/mol [71]. 

The early work on diazoamino rearrangements has been well summarized by Shine 3,244) Briefly, all the previous evidence supported an intermolecular, specifically acid-catalyzed process, the so-called Friswell-Green mechanism, postulated in 1884(1). Under certain conditions, particularly when not water, but the corresponding amine is used as solvent, a modification of this mechanism can occur. Thus Goldschmidt et al. found in 1924 that the decomposition of the protonated diazoamino compound to amine and diazonium ion can be catalyzed by the anion of the acid when the latter is weak, for example, nitrobenzoic acid. With mineral acids the anion is a weak nucleophile and no evidence was found for such a pathway, but it was postulated that here the amine itself can catalyze the fission of the protonated diazoamino compound. Neither of these processes has been observed in aqueous or partially aqueous solution, for example, in 95 % aqueous ethanol... 

Figure 7-14A). The base peak at m/z 305 might arise from the neutral loss of a 2-vinylamino-ethanol. The product ions formed by the neutral loss of 73 (2-methyleneamino-ethanol) and 44 (Ethenol) Da from the precursor ion of m/z 392 were also consistent with the proposed structure (Figure 7-15A). The production spectra of impurities D and E were similar in two ways. Both have a base peak at m/z 88 which was produced when an A-(2-hydroxyethyl) aminoethyl group was cleaved from the molecule. Both produce a less intense product ion that was 61 Da less than the precursor ion (Figure 7-15 m/z 278 in D, and m/z 263 in E). This 61-Da loss was found to be the loss of a 2-aminoethanol neutral. Further studies suggested that impurities D and E are photo-decomposition products of DuP 941[87]. Based on the LC/MS/MS data,... 

A method for the preparation of undoped ZnO films is by spray pyrolysis, using Zn(acac)2 H20 between 100 and 400 °C either with a dry solvent or in the presence of excess water. Above 200 °C, a change in the decomposition mechanism occurs and the films became more consolidated, transparent, have larger grains and are more conductive. Ultrafine ZnO particles of size less than 9 nm with a narrow size distribution were prepared by Zn(acac)2 and NaOH in ethanolic solution . The formation of stable ZnO nanoparticles is attributed to the stabilization of surface Zn + ions chelated by acac ligands and the presence of only a small amount of H2O. 

When 8-[(4-Cyanophenyl)imino]-87f-quinazolino[3,2-c][l,2,3]benzotriazine (13) is subjected to decomposition in ethanol, acetic acid, mineral acids, or acetic acid containing iodide, bromide, or azide ions, and 2-naphthol, 4-(4-cyanoanilino)-2-[2-(substituted)phenyl]quinazolines 14 are obtained. ... 

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