Types of decomposition

In the absence of air, TEE disproportionates violently to give carbon and carbon tetrafluoride the same amount of energy is generated as in black powder explosions. This type of decomposition is initiated thermally and equipment hot spots must be avoided. The flammability limits of TEE are 14—43% it bums when mixed with air and forms explosive mixtures with air and oxygen. It can be stored in steel cylinders under controlled conditions inhibited with a suitable stabilizer. The oxygen content of the vapor phase should not exceed 10 ppm. Although TEE is nontoxic, it may be contaminated by highly toxic fluorocarbon compounds. 

Thermal stability tables are available for the various amines, but they are of little practical value because decomposition products vary, depending on specific operating conditions. Morpholine is an exception, as the breakdown products are first DEA and then MEA, which is a particularly effective amine in some nuclear power plant facilities (PWRs). Thermal stability and the types of decomposition by-products only become important in boiler plants with superheaters operating in excess of 1,000 °F. 

The effect of structure of the alkyl group on the stability of monoalkyl-thallium(III) compounds can best be understood by reference to the different mechanisms by which these compounds undergo decomposition. A number of authors have attributed the instability of monoalkylthallium(III) compounds to facile C—T1 bond heterolysis and formation of carbonium ions [Eq. (25)] (52, 66, 79). This explanation is, however, somewhat suspect in cases where primary carbonium ions would be involved and either the two-step sequence shown in Eqs. (26), (27), or the fully synchronous 8 2 displacement shown in Eq. (28), is more compatible with the known facts. Examination of the oxythallation reactions that have been described reveals that Eq. (27) [or, for concerted reactions, Eq. (28)] can be elaborated, and that five major types of decomposition can be recognized for RTlXj compounds. These are outlined in Scheme 8, where Y, the nucleophile... 

Thus, we see that CCA forms a canonical analysis, namely a decomposition of each data set into a set of mutually orthogonal components. A similar type of decomposition is at the heart of many types of multivariate analysis, e.g. PCA and PLS. Under the assumption of multivariate normality for both populations the canonical correlations can be tested for significance [6]. Retaining only the significant canonical correlations may allow for a considerable dimension reduction. 

We have studied the thermal decomposition of diaryl ether in detail, since the cleavage of ether linkage must be one of the most responsible reactions for coal liquefaction among the various types of decomposition reaction and we found that the C-0 bond of polynucleus aromatic ethers is cleaved considerably at coal liquefaction temperature. 

In such decompositions the rate of decomposition mainly depends on the intensity and wave length of radiation and not much on temperature. Solvent plays an important role in this type of decomposition as it controls the intensity of the radiation incident on the initiator molecule. 

On pyrolysis, in addition to the expected C5 olefins, ethylcyclopropane also yields butadiene and methane (this constitutes an important reaction path, the yield of butadiene being about 20% of the total products). This type of decomposition is probably general for ethyl-substituted cyclopropanes, since 1,1-diethylcyclopropane yields 2-ethylbutadiene and methane as well as C7 olefins (Frey and Marshall, 1965). It is possible that the decomposition to the butadiene is also a simple unimolecular process via a transition state such as shown below. 

This is a major route of decomposition of ethyl 2-furyldiazoacetate (%) (R = H, = C02Et) when heated in dichloromethane or methanol (74JOC2939). The same type of decomposition has been observed with other 2-furylcarbenes which were generated by decomposition of the sodium salts of tosylhydrazones at 3(X)°C (78JA7927). Thermolysis of the diazo compound 96 (R = R = H) in cyclooctane or styrene gave, besides the open-chain acetylene 97, products of intermolecular carbene insertion. This led the authors to favor the carbene mechanism of ring-opening (path A in Scheme 7). 

Hydrolytic decomposition has already been discussed. A different type of decomposition of nitric esters occurs at elevated temperatures. More detailed information concerning this type of decomposition will be included in the descriptions of the individual esters properties, in particular those of nitroglycerine and nitrocellulose. 

A probable mechanism for the thermal decomposition of nitrocellulose has been suggested by Desmaroux [73] who assumed the occurrence of three types of decomposition reaction ... 

Another type of decomposition of metallanorbornadienes can arise in the case of derivatives incorporating certain substituents, in particular C=0 or CF3. They decompose by rearrangement with formation of stable Si—O or Si—F bonds123. These rearrangement reactions give several products depending on the solvent used. 

The energy of activation, calculated from the influence of temperature on the rate of the thermal decomposition, is estimated as 68,500 calories.30 If this value is correct there is ample energy available in the radiation to effect the same type of decomposition... 

These three examples all have the leaving group taking both electrons from the old O bond. This type of decomposition is sometimes called heterolytic fission or simply heterolysis and is the most common in organic chemistry. There is another way that a G bond can break. Rather than a pair of electrons moving to one of the atoms, one electron can go in cither direction. This is known as homolytic fission as two species of the same charge (neutral) will be formed. It normally occurs when... 

The substances that are produced in a decomposition reaction can be elements or compounds. In the simplest type of decomposition reaction, a compound breaks down into its component elements. One example is the decomposition of water into hydrogen and oxygen. This reaction occurs when electricity is passed through water. Figure 4.8 shows an apparatus set up for the decomposition of water. 

The same type of decomposition in the presence of NO yields substantial amounts of GeHsOGeHs, lending further support to the idea that reaction 32 is the main process . While the mercury photosensitized reaction is generally accepted to proceed primarily via Ge—H bond cleavage , a different process (equation 33) involving the initial formation of germylene, lGeH2, becomes the most important primary reaction under direct photochemical and thermal decomposition. 

Decomposition reactions have the opposite effect from combination reactions. In a decomposition reaction, a single compound can decompose to two elements, to an element and a simpler compound, to two simpler compounds, or (rarely) to another combination of products. Ternary componnds, compounds containing three elements, do not decompose into three uncombined elements. Decomposition reactions are easy to identify because there is only one reactant. Table 8.1 summarizes the most common types of decomposition reactions. 

Energy is provided to this endothermic reaction by the conduction, convection, and radiation from the furnace walls. This type of decomposition can also be caused on a hot substrate to produce a ceramic film. This process is called chemical vapor decomposition (CVD). 

From a chemical point of view, the AB decomposition in solution may allow one to adjust the type of decomposition product obtained after dehydrogenation and thus may influence the recycling strategy to be applied. Furthermore, benefits from improved kinetics can also be expected. Of course, the fundamental prerequisite is a high solubility and the stability of ammonia borane in the solvent in question. Corresponding data are given in Section 8.2. 

When polymerization is carried out at relatively high temperatures (t > 40° G.), thermally unstable compounds are frequently used as a source of free radicals. The persulfate ion, for example, decomposes with formation of two sulfate ion radicals 804 , a reaction which is strictly first-order at least in the absence of soap. In addition, another type of decomposition occurs at low pH where the H+ ion reacts with persulfate (37). Also soap is known to influence the rate of decomposition of persulfate. These last reactions, however, do not produce radicals (2, 38,63). 

While the products from the Tl(III) oxidation are entirely consistent with a simple heterolytic splitting of the Tl(III)-carbon bond in the oxythallation intermediate, the products of the Pd (II) oxidation are not consistent with this type of decomposition of the oxypalladation intermediate. If heterolytic splitting of the Pd (II)-carbon bond were taking place in aqueous solution, some glycol products would be expected yet none is ever found, even when a hydride shift is impossible— e.g., the oxypalladation adduct obtained by normal Markovnikov addi-... 

The third possibility involves solvolysis of a Pd(II)-carbon bond (Reaction 52). Although, as mentioned above, this type of decomposition does not seem to occur in simple Pd(II) alkyls, the presence of an a-hydroxyl would be expected to increase solvolysis rates greatly. However, the fact that the reaction of ClHgCH2CH20H with PdCl2 in non-aqueous solvent gives acetaldehyde (34) suggests that adduct decomposition does not occur by solvolysis. However, the decomposition of II could occur by removal of hydrogen by Pd(II) from the a-hydroxyl. 

In this section we examine various ways in which dmgs in both liquid and solid formulations can lose their activity, so that we can be aware of those chemical groups which, when present in dmg molecules, can cause stability problems. We will later see how to prevent or minimise the chemical breakdown for each type of decomposition process. Although each decomposition scheme is considered separately, it should be noted that with some drug molecules more than one type of decomposition may be occurring at the same time this, of course, complicates the analysis of the system. 

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