Acetate-induced decomposition

Chemical off—on switching of the chemiluminescence of a 1,2-dioxetane (9-benzyhdene-10-methylacridan-l,2-dioxetane [66762-83-2] (9)) was first described in 1980 (33). No chemiluminescence was observed when excess acetic acid was added to (9) but chemiluminescence was recovered when triethylamine was added. The off—on switching was attributed to reversible protonation of the nitrogen lone pair and modulation of chemically induced electron-exchange luminescence (CIEEL). Base-induced decomposition of a 1,2-dioxetane of 2-phen5l-3-(4 -hydroxyphenyl)-l,4-dioxetane (10) by deprotonation of the phenoHc hydroxy group has also been described (34). 

The alkylation of quinoline by decanoyl peroxide in acetic acid has been studied kineti-cally, and a radical chain mechanism has been proposed (Scheme 207) (72T2415). Decomposition of decanoyl peroxide yields a nonyl radical (and carbon dioxide) that attacks the quinolinium ion. Quinolinium is activated (compared with quinoline) towards attack by the nonyl radical, which has nucleophilic character. Conversely, the protonated centre has an unfavorable effect upon the propagation step, but this might be reduced by the equilibrium shown in equation (167). A kinetic study revealed that the reaction is subject to crosstermination (equation 168). The increase in the rate of decomposition of benzoyl peroxide in the phenylation of the quinolinium ion compared with quinoline is much less than for alkylation. This observation is consistent with the phenyl having less nucleophilic character than the nonyl radical, and so it is less selective. Rearomatization of the cr-complex formed by radicals generated from sources other than peroxides may take place by oxidation by metals, disproportionation, induced decomposition or hydrogen abstraction by radical intermediates. When oxidation is difficult, dimerization can take place (equation 169). 

In another study several simple silenes RR Si=CH2 (R, R = Me, Vinyl etc.) were formed by laser-powered pyrolysis and were found to form linear polymers, in contrast to the usual behavior of silenes which yield cyclodimers when formed by conventional thermolysis techniques16. Reactions of the silenes in the presence of several monomers such as vinyl acetate, allyl methyl ether and methyl acrylate were also studied. Laser-induced decomposition of silacyclobutane and 1,3-disilacyclobutane gave rise to silenes and other oxygen-sensitive deposits17,18. 

The mechanism proposed so far takes account of the induction period and initial stages of the reaction only, and it is difficult to see how it can account for the large amount of hydroperoxide decomposed by the sulfur compound. However, Tetralin hydroperoxide is decomposed catalytically by acids (5). Although in the absence of dilauryl thiodipropionate the decomposition of Tetralin hydroperoxide in the presence of acetic acid at 70 °C. was very slow, if the acid species is a much stronger acid than acetic—e.g., a sulfonic acid as seems likely from the nature of the products of the reaction, the rate of acid-induced decomposition may be comparable with the rate of decomposition by the sulfur compound. Some evidence that acid-induced decomposition does occur at some stage in the over-all reaction is found in the presence of an ortho substituted aromatic compound in the solid product of the reaction. The acid catalyzed decomposition of Tetralin hydroperoxide follows the path of Reaction 14 (5) to give y-(o-hydroxyphenyl)butyraldehyde. This forms a brown resin which is mainly the aldol of this aldehyde (cfthe resin obtained in this work). 

The 24 hour photolysis of chlorendic anhydride (III) in acetone in the presence of diethoxyacetophene (IV) yielded at least twelve measurable products as observed by the GC/MS procedure (Table I). Some of the products observed, i.e. 4-methyl-4-hydroxy-2-pentanone, biacetal, 4-methyl-3-pentene-2-one, ethyl acetate, 3-methyl-3-hy-droxy-2-butanone, 4-methyl-2-pentanone, and 2,4-pentane-dlone, are clearly derived from the photochemically induced decomposition of acetone and/or dlethoxyacetophe-none. 

Increases in temperature can also affect the stability of ions, resulting in fragmentation in ways reminiscent of electron impact ionization in MS. The earliest systematic report on such fragmentations was for butyl acetates thermalized ions were heated to induce decomposition, forming carboxylic acid fragments at 100-125°C. There was... 

By comparison to peroxides, the azo compounds are generally not susceptible to chemically induced decompositions. It was shown,however, that it is possible to accelerate the decomposition of a,a -azobisisobutyronitrile by reacting it with bis(-)-ephedrine-copper(II) chelate. The mechanism was postulated to involve reductive decyanation of azobisisobutyronitrile through coordination to the chelate. Initiations of polymerizations of vinyl chloride and styrene with a,a -azobisisobutyronitrile coupled to aluminum alkyls were investigated. Gas evolution measurements indicated some accelerated decomposition. Also, additions of large amounts of tin tetrachloride to either a,a -azobisisobutyronitrile or to dimethyl-a,a -azobisis-obutyrate increase the decomposition rates. Molar ratios of [SnCl4]/[AIBN]= 21.65 and [SnCl4]/[MAIB] = 19.53 increase the rates by factors of 4.5 and 17, respectively. Decomposition rates are also enhanced by donor solvents, like ethyl acetate or propionitrile in the presence of tin tetrachloride. ... 

Ethylene oxide also stabilizes against alkali-induced decomposition. Cyclic acetals or, for example, dimethyl formal are also good stabilizers against alkali attack ... 

Phenylphosphonic acid (1.58 g, 10 mmol) is added to a diluted solution of 40% tetrabutylammonium hydroxide (13 mL, 20 mmol) in water (100 mL) then a solution of H2W2O11 (21 mL, 20 mmol of tungsten), prepared as above, is added dropwise to the clear solution. The flaky solid that forms is collected, rinsed with cold water, and dried under vacuum at 40°C (heating above 60°C may induce decomposition of the peroxo salt). Yield 7.23 g (62%). An analytical sample was recrystallized from a mixture of 1,2-dichloroethane and ethyl acetate. 

Infrared spectroscopy and thermogravimetry have been used in polymer analysis for many years. By coupling the effluent of thermogravimetry to an infrared gas cell, TG/IR (sometimes known as evolved gas analysis) has been used to examine the thermally induced decomposition products a variety of polymers including of poly(vinyl chloride) (7), polyacrylamide (2), tetrafluoroethylene-propylene (3) and ethylene-vinyl acetate (4) copolymers, as well as styrene-butadiene composite (5). 

In this paper, the thermally induced decomposition of ethylene-vinyl acetate copolymers is examined. The analysis of the trapped effluents by GC/FT-IR is significantly different than that reported by other authors (4). These authors noted the formation of acetic acid and a polyolefin at 360 0 to 450 C, as is observed in... 

Acyl-aryl-nitrosamines decompose in benzene by a radical and an ionic path, and the relative efficiency of a series of alkenes in promoting the ionic path has been considered. This is illustrated by the decomposition of N-nitrosoacetanil-ide (169) and benzenediazonium acetate by two competing routes to give benzyne (by acetate-induced elimination), which can be trapped as the furan adduct (170), and phenyl radicals by a chain reaction (Scheme 26). 

The diazo function in compound 4 can be regarded as a latent carbene. Transition metal catalyzed decomposition of a diazo keto ester, such as 4, could conceivably lead to the formation of an electron-deficient carbene (see intermediate 3) which could then insert into the proximal N-H bond. If successful, this attractive transition metal induced ring closure would accomplish the formation of the targeted carbapenem bicyclic nucleus. Support for this idea came from a model study12 in which the Merck group found that rhodi-um(n) acetate is particularly well suited as a catalyst for the carbe-noid-mediated cyclization of a diazo azetidinone closely related to 4. Indeed, when a solution of intermediate 4 in either benzene or toluene is heated to 80 °C in the presence of a catalytic amount of rhodium(n) acetate (substrate catalyst, ca. 1000 1), the processes... 

Fell and Bari (89) also studied the rhodium-catalyzed reaction. A rho-dium-N-methylpyrrolidine-water catalyst system was very effective for producing the propane-1,2-diol acetate directly. The best yields (>90%) of product of about 9 1 alcohol aldehyde ratio were obtained in the region of 95°-l 10°C. This range was very critical, as were other reaction parameters. Rhodium alone gave the best yield of aldehyde (83%) at 60°C. Triphenylphosphine as cocatalyst induced the decomposition of the aldehyde product. 

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