Acetic acid ions, decomposition

The consistancy of the observed /4-factors, the magnitude of the activation entropies, the a correlations in the substituent effects at the a- and /8-carbon positions, the collective influence of all three substitutable centers on the reaction rates, the importance of charge stabilization in the transition state, and the primary deuterium isotope effects on the alkyl acetic acid ester decomposition, all favor the concerted polar 6-center transition state shown below (IV). However, an alternative possibility involving intimate ion-pair formation has been proposed by Scheer et al.. ... 

When diazomethane is slowly added to excess lactam, the anions formed can interact with unreacted lactam by means of hydrogen bonds to form ion pairs similar to those formed by acetic acid-tri-ethylamine mixtures in nonpolar solvents. The methyldiazonium ion is then involved in an ion association wdth the mono-anion of a dimeric lactam which is naturally less reactive than a free lactam anion. The velocity of the Sn2 reaction, Eq. (7), is thus decreased. However, the decomposition velocity of the methyldiazonium ion, Eq. (6a), is constant and, hence, the S l character of the reaction is increased which favors 0-methylation. It is possible that this effect is also involved in kinetic dependence investigations have shown that with higher saccharin concentrations more 0-methylsaccharin is formed. 

Salts of diazonium ions with certain arenesulfonate ions also have a relatively high stability in the solid state. They are also used for inhibiting the decomposition of diazonium ions in solution. The most recent experimental data (Roller and Zollinger, 1970 Kampar et al., 1977) point to the formation of molecular complexes of the diazonium ions with the arenesulfonates rather than to diazosulfonates (ArN2 —0S02Ar ) as previously thought. For a diazonium ion in acetic acid/water (4 1) solutions of naphthalene derivatives, the complex equilibrium constants are found to increase in the order naphthalene < 1-methylnaphthalene < naphthalene-1-sulfonic acid < 1-naphthylmethanesulfonic acid. The sequence reflects the combined effects of the electron donor properties of these compounds and the Coulomb attraction between the diazonium cation and the sulfonate anions (where present). Arenediazonium salt solutions are also stabilized by crown ethers (see Sec. 11.2). 

Oxidation of the steroidal olefin (XXVII) with thallium(III) acetate gives mainly the allylic acetates (XXXI)-(XXXIII) (Scheme 15), again indicating that trans oxythallation is the preferred reaction course (19). Addition of the electrophile takes place from the less-hindered a-side of the molecule to give the thallinium ion (XXVIII), which by loss of a proton from C-4 would give the alkylthallium diacetate (XXIX). Decomposition of this intermediate by a Type 5 process is probably favorable, as it leads to the resonance-stabilized allylic carbonium ion (XXX), from which the observed products can be derived. Evidence in support of the decomposition process shown in Scheme 15 has been obtained from a study of the exchange reaction between frawr-crotylmercuric acetate and thallium(III) acetate in acetic acid (Scheme 16) (142). 

Ab initio methods, 147-49 Acetate ion, decomposition, 135 Acetylene, interaction with palladium, tunneling spectroscopy, 435,437f Acid-dealuminated Y zeolites catalytical properties, 183 sorption, 175-78 Acid sites, on zeolites, 254 acidification effects, 266 Acoustic ringing, in NMR, elimination, 386 Active sites, nature, 104 Activity measurements, Co-Mo catalysts, 74 Adsorbed molecules,... 

Experiments.—In order to learn, at least qualitatively, the influence of the hydrogen ion concentration on the velocity of decomposition, about 0-5 c.c. of ethyl diazoacetate is dissolved in a little 50 per cent alcohol and the solution is divided into two portions in small beakers to which respectively 1 c.c. of 0-1 AT-hydrochloric acid and 1 c.c. of 0-1 N-acetic acid (prepared in a measuring cylinder from glacial acetic acid) are added. 

The reactions obeyed pseudo-first-order kinetics consistent with a rapid reversible protonation of the substrate, S, at the ester carbonyl followed by a rate-determining decomposition to acetic acid and nitrenium ion according to Scheme 19. In accordance with equation 13, the pseudo-first-order rate constant, k, was shown to be proportional to acid concentration and inversely proportional to the activity of the water/acetonitrile solvent . 

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). 

To understand the significant effect of catalyst nature, a better understanding of the main reactions, peracetic acid decomposition, and its reaction with acetaldehyde was needed. A literature -survey showed that the kinetics were not well studied, most of the work being done at very low catalyst concentration 1 p.p.m.), and there is disagreement with respect to the kinetic expressions reported by different authors. The emphasis has always been on the kinetics but not on the products obtained, which are frequently assumed to be only acetic acid and oxygen. Consequently, the effectiveness of a catalyst was measured only by the rates and not by the significant amount of by-products that can be produced. We have studied the kinetics of these reactions, supplemented by by-product studies and experiments with 14C-tagged acetaldehyde and acetic acid to arrive at a reaction scheme which allows us to explain the difference in behavior of the different metal ions. 

Oxidation of Acetaldehyde. When using cobalt or manganese acetate the main role of the metal ion (beside the initiation) is to catalyze the reaction of peracetic acid with acetaldehyde so effectively that it becomes the main route to acetic acid and can also account for the majority of by-products. Small discrepancies between acetic acid efficiencies in this reaction and those obtained in acetaldehyde oxidation can be attributed to the degradation of peracetoxy radicals—a peracetic acid precursor— by Reactions 14 and 16. The catalytic decomposition of peracetic acid is too slow (relative to the reaction of acetaldehyde with peracetic acid) to be significant. The oxidation of acetyl radical by the metal ion in the 3+ oxidation state as in Reaction 24 is a possible side reaction. Its importance will depend on the competition between the metal ion and oxygen for the acetyl radical. 

Addition of chloride ions (as solid calcium chloride, potassium chloride or sodium chloride) to aqueous solutions containing 40% of peroxyacetic acid and 1 % of acetic acid leads to a violently exothermic decomposition reaction. Chlorine is evolved, most of the liquid evaporates and the residue (often red coloured) deflagrates. 

The only definite borate hydrates of cobalt are the CoO - 3B203 - 8H20 and CoO 3B203 10H2O compounds. The octahydrate is prepared by evaporation of acetic acid from cobalt acetate-boric acid mixtures, or by mixing aqueous solutions of cobalt chloride, borax, and boric acid (206). The 1 3 7.5 borate can form as a solid solution and, in the presence of 3% boric acid, affords the decahydrate (117). The crystal structure determination of this 1 3 10 compound shows it to possess the hexaborate ion (380). The IR spectra (402) and thermal decomposition (396) of these compounds have been determined. 

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. 

It was found impossible to measure the rate of decomposition by the evolution of gases because the release of these gas bubbles is very slow and erratic. The course of the reaction was followed by analyzing samples for the ammonium ion. Small amounts of the decomposing amalgam were forced through a capillary tube into a chilled solution of an iodate. The ammonium reacted with iodate ion to give iodide ion. The solution was then acidified with acetic acid and the iodine distilled out, collected and titrated with sodium thiosulfate. The method was checked with samples... 

Metastable 1- and 2-tetralol ions have been found to lose water by specific 1, 4 and 1, 3 eliminations, respectively. Using a type of internal reference method, an isotope effect of 2.0 on loss of water relative to total metastable ion decompositions was obtained for 1-tetralol [345]. The acetoxy derivatives of 1- and 2-tetralol lose acetic acid by specific mechanisms and no isotope effect was observed in either case [923]. 

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