Slow Decomposition

The diazomethane-ether solution should be dry. If in doubt, it may be dried with A.R. potassium hydroxide pellets. The anhydrous ethereal solution may be stored in a smooth glass flask or bottle in a refrigerator for a week or so since slow decomposition occurs with hberation of gas, the containing vessel should be protected by a calcium chloride (or cotton wool) guard tube. 

The cases of pentamethylbenzene and anthracene reacting with nitronium tetrafluoroborate in sulpholan were mentioned above. Each compound forms a stable intermediate very rapidly, and the intermediate then decomposes slowly. It seems that here we have cases where the first stage of the two-step process is very rapid (reaction may even be occurring upon encounter), but the second stages are slow either because of steric factors or because of the feeble basicity of the solvent. The course of the subsequent slow decomposition of the intermediate from pentamethylbenzene is not yet fully understood, but it gives only a poor yield of pentamethylnitrobenzene. The intermediate from anthracene decomposes at a measurable speed to 9-nitroanthracene and the observations are compatible with a two-step mechanism in which k i k E and i[N02" ] > / i. There is a kinetic isotope effect (table 6.1), its value for the reaction in acetonitrile being near to the... 

Although thiosulfate is one of the few reducing titrants not readily oxidized by contact with air, it is subject to a slow decomposition to bisulfite and elemental sulfur. When used over a period of several weeks, a solution of thiosulfate should be restandardized periodically. Several forms of bacteria are able to metabolize thiosulfate, which also can lead to a change in its concentration. This problem can be minimized by adding a preservative such as Hgl2 to the solution. 

A freshly made solution behaves as a strong monobasic acid. Neutralized solutions slowly become acidic because of hydrolysis to monofluorophosphoric acid and hydrofluoric acid. The anhydrous acid undergoes slow decomposition on distillation at atmospheric pressure, reacts with alcohols to give monofluorophosphoric acid esters, and is an alkylation (qv) and a polymerization catalyst. 

Pure diketene is stable for several weeks if stored at or below 0°C in an aluminum or stainless steel container. Glass should be avoided because of its inherent basicity which favors slow polymerization. Above 15°C slow decomposition occurs and the color becomes progressively darker. Pressure buHd-up Upon prolonged exposure to heat is possible. Heating and contamination of the container, especiaHy by acids, bases, and water, should be avoided. Residual vapors in empty containers are hazardous and may explode on ignition. 

Diketene is a flammable Hquid with a flash point of 33°C and an autoignition temperature of 275°C. It decomposes rapidly above 98°C with slow decomposition occurring even at RT. The vapors are denser than air (relative density 2.9, air air = 1). The explosive limits in air are 2—11.7 vol % (135). In case of fire, water mist, light and stabilized foam, as well as powder of the potassium or ammonium sulfate-type should be used. Do not use basic extinguisher powders and do not add water to a closed container. 

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

Dioxazine Violet. Carba2ole Dioxa2ine Violet is prepared by the reaction of two moles of 2-ainino-A/-ethylcarba2ole with chloranil. This violet may be used in most plastics for shading phthalocyanine blues, because it has comparable light fastness. At relatively high temperatures, it may be subject to slow decomposition. 

Oxaziridines substituted in the 2-position with primary or secondary alkyl groups undergo decomposition at room temperature. In the course of some weeks, slow decomposition of undiluted compounds occurs, the pattern of which is analogous to that of acidic or alkaline N—O cleavage (Sections 5.08.3.1.3 and 4), Radical attack on a C—H bond in (109) effects N—O cleavage, probably synchronously (57JA5739). In the example presented here, methyl isobutyl ketone and ammonia were isolated after two hour s heating at 150 °C. 

Ammonium perchlorate [7790-98-9] M 117.5, d 1.95, pK -2.4 to -3.1 (for HCIO4). Crystd twice from distilled water (2.5mL/g) between 80° and 0°, and dried in a vacuum desiccator over P2O5. Drying at 110° might lead to slow decomposition to chloride. POTENTIALLY EXPLOSIVE. 

Chemical Reactivity - Reactivity with Water No reaction unless in the presence of acids and caustics Reactivity with Common Materials Slow decomposition occurs, but generally the reactions are not hazardous Stability During Transport Stable if cool Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Violent, exothermic polymerization occurs at about 225 of. Acid fumes will also cause polymerization at ordinary temperatures Inhibitor of Polymerization None reported. 

The reaction described here is probably responsible for the slow decomposition of many oxaziranes at room temperature, 2-fert-Alkyl-oxaziranes are stable at room temperature for unlimited periods radical attack on the a-C-atom of the iV-alkyl group is not possible. By contrast, oxaziranes containing a C—H group which is alpha to the N-atom are unstable at room temperature on keeping they are largely decomposed within a few weeks. 

The sequences of radioactive decays that lead to lead are well-known and the rates of decay have been carefully measured. We shall consider the sequence based upon the relatively slow decomposition of the most abundant uranium isotope, mass 238 (natural abundance, 99%) ... 

Before dealing with these, it is necessary to refer briefly to the stability of thiosulphate solutions. Solutions prepared with conductivity (equilibrium) water are perfectly stable. However, ordinary distilled water usually contains an excess of carbon dioxide this may cause a slow decomposition to take place with the formation of sulphur ... 

Li, Z., and Meighen, E. A. (1994). The turnover of bacterial luciferase is limited by a slow decomposition of the ternary enzyme-product complex of luciferase, FMN, and fatty acid. J. Biol. Chem. 269 6640-6644. 

K.K. Andreev, Slow Decomposition of Explosives and Tests of Chemical Stability , ComptRendCongrlnternChimlnd 31, Liege... 

Caesium azide melts with a little decomposition (<1%) at 598 K. There is slow decomposition of the solid when large amounts of NiO are present [714], Observations on the photolyses of RbN3 and CsN3 have been discussed [715] with reference to the pyrolyses of other alkali azides. 

Similar mechanisms of course can be written for the reaction with the other hydrogen halide acids, and indeed for the relatively slow decomposition of N-chloroacetanilide in solutions of other strong acids15, viz. 

A second crystallization from dichloromethane-pentane is sometimes necessary to achieve material having this melting point. Styrene glycol dimesylate must be stored in a refrigerator, since slow decomposition takes place at room temperature. 

Similar divergences are found for lithium poly-2,4-hexadiene solution (1 10-3 M in living polymers) for which a sixfold decrease of viscosity upon protonation corresponding to a degree of association of 1.7 was reported 113), whereas only a threefold decrease, i.e. a degree of association of 1.4 was indicated earlier 1,8). The difference between the 1.7 and 1.4 values was tentatively attributed to a slow decomposition of the active ends over a period of two weeks U8) notwithstanding their reported good... 

A more detailed investigation of the thermal behavior of the exploding [ ]rotanes by differential scanning calorimetry (DSC) measurements performed in aluminum crucibles with a perforated lid under an argon atmosphere revealed that slow decomposition of exp-[5]rotane 165 has already started at 90 °C and an explosive quantitative decomposition sets on at 150 °C with a release of energy to the extent of AH(jecomp = 208 kcal/mol. Exp-[6]rotane 166 decomposes from 100°C upwards with a maximum rate at 154°C and an energy release of AH(jg on,p=478 kcal/mol. The difference between the onset (115°C) and the maximum-rate decomposition temperature (125-136°C) in the case of exp-[8]rotane 168 is less pronounced, and AHjecomp 358 kcal/mol. The methy-... 

The formal cyclodimer of o-iodoethynylbenzene, diyne (7), was prepared in 1974 by Sondheimer s group using analogous bromination/dehydrobromina-tion chemistry [13]. The highly strained molecule was comparatively stable, decomposing around 110°C on attempted melting. Slow decomposition of the solid was observed after 2 days, when unprotected from light and air. 

Slow decomposition of a chemical of limited stability. Eor example, the slow decomposition of 98-100% formic acid to gaseous carbon monoxide in a full 2.5 litre bottle would produce 7 bar pressure during one year at 25 °C if unvented ... 

Deflagration. In high explosives, a relatively slow decomposition accompanied by fumes but not normally by flame. 

This compound, readily formed by iodine oxidation of azidodithioformic acid or its salts, is a powerful explosive. It is sensitive to mechanical impact or heating to 40°C, and slow decomposition during storage increases the sensitivity. Preparative precautions are detailed. 

A 70 g sample, sealed into a brown glass ampoule, exploded after storage at ambient temperature for 17 years. This was attributed to slow decomposition and gas generation (perhaps initiated by traces of alkali in the ampoule glass). 

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