Unstable product decomposition

Strong acid + carbonate or hydrogen carbonate Unstable product + decomposition Double-replacement -E decomposition Salt + H2O -E CO2 Salt -E H2O -E CO2 H+ + CO32-H+ -E HCO3- H2O + CO2 H2O + CO2... 

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

This intermediate (or its ethyl homologue), produced dining the preparation of phosphoryl dichloride isocyanate from interaction of phosphorus pentachloride and methyl (or ethyl) carbamate, is unstable. Its decomposition to the required product may be violent or explosive unless moderated by presence of a halogenated solvent. 

Vessels for microwave-assisted chemistry are usually made from thermal insulators such as PEEK, quartz, borosilicate glass or PTFE. Thus, the benefits of rapid heating can be diminished if the opportunity for workup is delayed by slow cooling. Decomposition of thermally unstable products also can occur. 

The oxidation of 104 occurs readily with 1 equiv of manganese dioxide in 4 h to give seco-pz (162) (77%). Prolonged reaction times, or the use of an excess of the oxidant, results in reduced yields of 162, along with some second pyrrole cleavage and decomposition. If pz 104 is treated with 2 equiv of manganese dioxide for 24 h, the rather unstable product of overoxidation, diseco-porphyrazine 163 can isolated in up to 41% yield (Scheme 30) (8). 

Searching for ways of getting rid of these products, a method was worked out by which their decomposition was induced under strictly controlled conditions. Decomposition is caused, ifor instance, by pouring the mixture into hot water after nitration. The amount of water and the temperature are coordinated so that a concentration of 50-55% HN03 and a temperature of 70-90°C are maintained. Highly pure cyclonite is precipitated and N02 evolved from the decomposition of all unstable products. This is the so-called degassing process . 

A stability test is made after 2 hours drying at 100 °C hi order to ascertain the drop in active chlorine content. A stable product manufactured in Moore s equipment shows a loss of 3.5 per cent while an unstable product about 14 per cent. From this we can see that although decomposition is suppressed to a considerable extent in the case of a stable product, the active chlorine loss is still noticeable. The so called superstable bleaching powder is prepared by the addition of quick lime to the stable product. A stability test then shows active chlorine loss to be less than 0.75 per cent. 

Now what happens with the carbon atom In the ground state the four L electrons are distributed over a lone pair in the lowest energy state (2s), and one unpaired bonding electron in each of two p levels. Thus one would expect CH2 as a hydrogen compound to have a structure like that of water. Actually methylene exists as a very unstable product formed, among others, in the decomposition of ketene, CH2=C=0, but carbon is nevertheless predominantly quadrivalent. How can this be explained ... 

SeOF4 is prepared by vacuum decomposition of pure sodium pentafluoroorthoselenate (equation 38). The volatile rather unstable product is trapped at —196 °c. ... 

The attacks of heterocyclic A -oxides, e.g. of pyridine, quinoline, isoquinoline, phenanthridine, etc., on activated alkynes (RC CR R = R = COOMe R = Ph, R = COOEt R = Ph, R = CN) pose similar problems . An acyclic intermediate has been postulated but is rarely detected. Some of the possibilities are illustrated in equation (126) . If the open intermediate is formed, then the paths to the ylid and the 2-substituted quinoline in equation (126) seem simple enough, but several possible mechanisms can lead to the 3-substituted products . Other workers regard the reaction of the nitrone (or azomethine oxide) with alkyne as simple cycloadditions - which yield 2,3-dihydro-l,2-oxazoles since these are often unstable, only decomposition products may be found (equation 127). The construction of the indolizine skeleton initiated by a similar process has been reviewed (equation 128). ... 

Various foodstuffs loose their original, beneficial flavor, aroma, taste, and color on processing. It is a common result of evaporation of volatile components or decomposition of certain food components under the influence of oxygen or light. In this manner the quality of foodstuffs decreases. In order to avoid such effects, volatile and unstable products are either protected in processed sources or, after processing, are supplemented by fragrances, colorants, and other components. 

In Runs 10 and 12 the precipitate was very heavy and the total soluble base was quite low. In those two instances the product was apparently insoluble or the lithiated tertiary amine structure too unstable and decomposition resulted. 

Some workers believe that adiabatic compression of interstitial gases is not important [38-40], because the shock sensitivity of some explosives is approximately the same for both vacuum and atmospheric pressure conditions. They consider that when an explosive is placed under vacuum it contains no interstitial gas. However, recent work showed that during the fracture of thermally unstable crystals decomposition products are produced [41,42]. The amount of products depended on the surface area created by fracture, the velocity of the fracture, and the crystal type. With lead azide the gases produced were equivalent... 

Over the whole temperature range that is technically reasonable, the most desired product ethene is thermodynamically unstable against decomposition to the elements C and H2. The same is also true for other technically important alkenes and aromatics. 

Unexpectedly we find that the bromate(V) ion in acid solution (i.e. effectively bromic(V) acid) is a more powerful oxidising agent than the chlorate(V) ion, CIO3. The halates(V) are thermally unstable and can evolve oxygen as one of the decomposition products. Potassium chlorate(V), when heated, first melts, then resolidifies due to the formation of potassium chlorate(VII) (perchlorate) ... 

Pd(II) compounds coordinate to alkenes to form rr-complexes. Roughly, a decrease in the electron density of alkenes by coordination to electrophilic Pd(II) permits attack by various nucleophiles on the coordinated alkenes. In contrast, electrophilic attack is commonly observed with uncomplexed alkenes. The attack of nucleophiles with concomitant formation of a carbon-palladium r-bond 1 is called the palladation of alkenes. This reaction is similar to the mercuration reaction. However, unlike the mercuration products, which are stable and isolable, the product 1 of the palladation is usually unstable and undergoes rapid decomposition. The palladation reaction is followed by two reactions. The elimination of H—Pd—Cl from 1 to form vinyl compounds 2 is one reaction path, resulting in nucleophilic substitution of the olefinic proton. When the displacement of the Pd in 1 with another nucleophile takes place, the nucleophilic addition of alkenes occurs to give 3. Depending on the reactants and conditions, either nucleophilic substitution of alkenes or nucleophilic addition to alkenes takes place. 

Little work has been carried out on thiazole N-oxides. These products are unstable and breakdown by autoxidation to give thiazolium-A -oxide sulfates and other decomposition products (264). They are prepared by direct oxidation with hydrogen peroxide, or by tungstic acid (264, 265) or peracetic acid (265-267). 

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