Types of decomposition reaction

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. 

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 ... 

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. 

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. 

One of the original uses of modern EGD was to aid in the interpretation of DTA data. Using simultaneous DTA-EGD. Ayres and Bens (20) found that if an EGD peak was absent, while the DTA curve contained an endothermic or exothermic peak, it could be concluded that some type of phase transition had occurred in the sample. If curve peaks were found over the same temperature region for both EGD and DTA curves, some type of decomposition reaction involving volatile reaction products had occurred. A comparison of EGD and DTA curves is given in Table 8.1. Note that fusion and solid t - ... 

Absence of Induction and Acceleration Stages There are two types of decomposition reactions for which the stages of induction and acceleration cannot exist in principle. The first type includes those decompositions which do not produce low-volatility products, and, hence, in which the reaction interface between two solid phases is absent. The second type includes the decompositions of... 

Usually electropolymerization of these monomers occurs without any problems, and the properties of the subsequent polymers are detailed in Section 18.3.3. However, in very few occasions, the classical electropolymerization reaction does not work. This has been especially demonstrated in the case of tetrazines [121], where probably the too strong electron attracting character of the tetrazine impedes the classical cation-radical coupling, favoring another type of decomposition reaction, e.g., a proton loss. However, while even EDOT functionalized tetrazine does not polymerize, the same tetrazine ring can be incorporated into an ECP with the help of a bithienyl functionalized moiety [97]. 

Most decomposition reactions take place only when energy in the form of electricity or heat is added. Examples of several types of decomposition reactions are given in the following sections. 

We hope that this chapter has provided the reader with a useful overview of the synthesis of NHC-containing complexes, the activation of these complexes to form active catalysts, the types of decomposition reaction to which NHCs are suseeptible and the various methods that can be used to prevent, limit, or harness such reactions. 

The desire to understand catalytic chemistry was one of the motivating forces underlying the development of surface science. In a catalytic reaction, the reactants first adsorb onto the surface and then react with each other to fonn volatile product(s). The substrate itself is not affected by the reaction, but the reaction would not occur without its presence. Types of catalytic reactions include exchange, recombination, unimolecular decomposition, and bimolecular reactions. A reaction would be considered to be of the Langmuir-Hinshelwood type if both reactants first adsorbed onto the surface, and then reacted to fonn the products. If one reactant first adsorbs, and the other then reacts with it directly from the gas phase, the reaction is of the Eley-Ridel type. Catalytic reactions are discussed in more detail in section A3.10 and section C2.8. 

In the iavestigation of the decomposition reaction of aryldia2onium tetrafluoroborates ia nitroben2ene, it was found that ia addition to uoroben2ene, 3,3 -dinitrobiphenyl was formed (67). An ionic type of arylation reaction seems to take place. Decomposition of aryldia2onium tetrafluoro-, tetrachloro-, and tetrabromoborates ia aromatic solvents leads to electrophilic ring arylation (68). 

Enzymes are proteins of high molecular weight and possess exceptionally high catalytic properties. These are important to plant and animal life processes. An enzyme, E, is a protein or protein-like substance with catalytic properties. A substrate, S, is the substance that is chemically transformed at an accelerated rate because of the action of the enzyme on it. Most enzymes are normally named in terms of the reactions they catalyze. In practice, a suffice -ase is added to the substrate on which die enzyme acts. Eor example, die enzyme dial catalyzes die decomposition of urea is urease, the enzyme dial acts on uric acid is uricase, and die enzyme present in die micro-organism dial converts glucose to gluconolactone is glucose oxidase. The diree major types of enzyme reaction are ... 

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... 

Another interesting example is SHMT. This enzyme catalyzes decarboxylation of a-amino-a-methylmalonate with the aid of pyridoxal-5 -phosphate (PLP). This is an unique enzyme in that it promotes various types of reactions of a-amino acids. It promotes aldol/retro-aldol type reactions and transamination reaction in addition to decarboxylation reaction. Although the types of apparent reactions are different, the common point of these reactions is the formation of a complex with PLP. In addition, the initial step of each reaction is the decomposition of the Schiff base formed between the substrate and pyridoxal coenzyme (Fig. 7-3). 

The second type of simple reaction is decomposition. This reaction is also easy to recognize. Typically, only one reactant is given. A type of energy, such as heat or electricity, may also be indicated. This reactant decomposes to its elements, to an element and a simpler compound, or to two simpler compounds. Binary compounds may yield two elements or an element and a simpler compound. Ternary (three-element) compounds may yield an element and a compound or two simpler compounds. These possibilities are shown in Fig. 7.2. 

Rate Expressions for Enzyme Catalyzed Single-Substrate Reactions. The vast majority of the reactions catalyzed by enzymes are believed to involve a series of bimolecular or unimolecular steps. The simplest type of enzymatic reaction involves only a single reactant or substrate. The substrate forms an unstable complex with the enzyme, which subsequently undergoes decomposition to release the product species or to regenerate the substrate. 

Several other types of photochemical reactions involving unsaturated carbohydrates have been reported. One of these is38 photochemical, E -Z isomerization of the groups attached to a double bond (see Scheme 5). A second is the internal cycloaddition between two double bonds connected by a carbohydrate chain.39-41 Although the carbohydrate portion of the molecule is not directly involved in this cycloaddition, its presence induces optical activity in the cyclobutane derivatives produced photochemically. Finally, a group of acid-catalyzed addition-reactions has been observed for which the catalyst appears to arise from photochemical decomposition of a noncarbohydrate reactant.42-44... 

Numerous types of chemical reactions pose potential hazards. Literature and incident data highlight the hazards of common industrial reactions, such as polymerization, decomposition, acid-base, oxidation-reduction (redox), and reactions with water. Polymerization and decomposition can be classified as self-reactions because they often involve just one chemical substance. However, other... 

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. 

In your previous chemistry course, you classified reactions into four main types synthesis, decomposition, single displacement, and double displacement. You also learned to recognize combustion reactions and neutralization reactions. You have now learned to classify redox reactions. In addition, you have also learned about a special type of redox reaction known as a disproportionation reaction. 

Anaerobic. A type of chemical reaction that occurs in the absence of oxygen such as the fermentation of sugars by yeast or decomposition of sewage sludge by microorganisms. 

This type of autocatalytic reaction is a simplification of many biological reactions such as fermentation, where the reaction produces products (species B in the previous example), which accelerates the rate. In fermentation, yeast cells in the solution produce enzymes that catalyze the decomposition of sugar to produce ethanol as a byproduct of yeast reproduction. Since the yeast population increases as the reaction proceeds, the enzyme concentration increases, and the process appears to be autocatalytic. A highly simplified description of fermentation might be... 

There are four types of H2S reactions decomposition, precipitation, oxidation, and organic addition. 

In this part of the chapter, we will briefly outline the main types of CL reactions which can be functionally classified by the nature of the excitation process that leads to the formation of the electronically excited state of the light-emitting species. Direct chemiluminescence is the term employed for a reaction in which the excited product is formed directly from the unimolecular reaction of a high-energy intermediate that has been formed in prior reaction steps. The simplest example of this type of CL is the unimolecular decomposition of 1,2-dioxetanes, which are isolated HEI. Thermal decomposition of 1,2-dioxetanes leads mainly to the formation of triplet-excited carbonyl compounds. Although singlet-excited carbonyl compounds are produced in much lower yields, their fluorescence emission constitutes the direct chemiluminescence emission observed in these transformations under normal conditions in aerated solutions ... 

Chemical vapor deposition (CVD) involves the reaction of gaseous reactants to form solid products. There are two general types of CVD processes (a) the thermal decomposition of a homogeneous gas to form a solid and (b) the chemical reaction of two or more gaseous species to form a solid. Both types of CVD reactions are used industrially to form a variety of important elements and compounds for semiconductor, superconductor, and ceramic coating applications. 

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