Decomposition pyrolytic

Pyrolytic Decomposition. The pyrolytic decomposition at 350—460°C of castor oil or the methyl ester of ricinoleic acid spHts the ricinoleate molecule at the hydroxyl group forming heptaldehyde and undecylenic acids. Heptaldehyde, used in the manufacture of synthetic flavors and fragrances (see Elavors and spices Perfumes) may also be converted to heptanoic acid by various oxidation techniques and to heptyl alcohol by catalytic hydrogenation. When heptaldehyde reacts with benzaldehyde, amyl cinnamic aldehyde is produced (see Cinnamic acid, cinnamaldehyde, and cinnamyl... 

Because of the possibility of focusing laser beams, tlrin films can be produced at precisely defined locations. Using a microscope train of lenses to focus a laser beam makes possible tire production of microregions suitable for application in computer chip production. The photolytic process produces islands of product nuclei, which act as preferential nucleation sites for further deposition, and tlrus to some unevenness in tire product film. This is because the subsuate is relatively cool, and therefore tire surface mobility of the deposited atoms is low. In pyrolytic decomposition, the region over which deposition occurs depends on the drermal conductivity of the substrate, being wider the lower the thermal conductivity. For example, the surface area of a deposit of silicon on silicon is nanower dran the deposition of silicon on silica, or on a surface-oxidized silicon sample, using the same beam geomeU y. 

A third category of syn eliminations involves pyrolytic decomposition of esters with elimination of a carboxylic acid. The pyrolysis of acetate esters normally requires temperatures above 400° C and is usually a vapor phase reaction. In the laboratory this is done by using a glass tube in the heating zone of a small furnace. The vapors of the reactant are swept through the hot chamber by an inert gas and into a cold trap. Similar reactions occur with esters derived from long-chain acids. If the boiling point of the ester is above the decomposition temperature, the reaction can be carried out in the liquid phase, with distillation of the pyrolysis product. 

Norchrysanthemic acid (35) was first synthesized by Staudinger in 1924 [16] as the pyrolytic decomposition product of chrysanthemun dicarboxylic acid (36) (Scheme 6). In the 1970s, Ohno and Elliott independently reported [17] insecticidal norchrysanthemic acid esters and these norchrysanthemic acid esters showed comparable insecticidal activity to the corresponding chrysanthemates (Fig. 3). 

The acid moiety of metofluthrin is (T/ )-norchrysanthemic acid. In this section we describe the development of synthetic studies of Z-rich norchrysanthemic acid. Aforementioned norchrysanthemic acid was first synthesized by Staudinger in 1924 as the pyrolytic decomposition product of chrysanthemun dicarboxylic... 

A third category of syn eliminations involves pyrolytic decomposition of esters with elimination of a carboxylic acid. The pyrolysis of acetate esters normally requires temperatures above 400° C. The pyrolysis is usually a vapor-phase reaction. In the... 

Substantially fewer studies have been published for the reactions of alkyl-substituted heteroaromatics, although these compounds also have implications for coal combustion. Several references discussed in the previous section contain information on methylated heteroaromatic rings. Mackie and coworkers completed experimental and theoretical studies of the pyrolytic decomposition of 2-picoline (2-methylpyridine). They concluded that decomposition proceeded mainly through o-pyridinyl and 2-picolinyl radicals. The former tended to decompose predominantly to yield cyanoacetylene, while the latter favored decomposition to a cyano-functionalized cyclopentadiene (Fig. 16). 

The molten material attacks quartz. Therefore, quartz boats coated with carbon by pyrolytic decomposition of methane should be used in refining the compound to obtain high purity material. 

Thin vitreous silica films are usually formed by vapor deposition or r-f sputtering (see Thin films, film-deposition techniques). Vapor deposition is generally effected by the pyrolytic decomposition of tetraethoxysilane or another alkoxysilane. Silica has been most extensively used in r-f sputtering of... 

Although other methods of preparation, involving the hydrogenation of carbon oxides, the pyrolytic decomposition of formates etc, have been patented, ihey do not appear to have achieved commercial importance... 

Pyrolytic decomposition of cyclic carbonate eaten of 1,2-diols hjus been utilized on occasion for epoxide synthesis. Ethylene Oxide jiml glycidol, for example, have been prepared26 mc from ethylene carbonate and glyceryl carbonate respectively (Eq. 314). 

As very few examples of metal haloxanthates are known, the preparation of copper(II) halo-xanthates is worthy of mention.96 Pyrolytic decomposition of metal xanthates has been found to produce alkenes.97... 

Density functional theory was used to show that unimolecular formation of CO2 and dihydroxycarbene from oxalic acid has a barrier of 31 kcal mol-1.33 The barrier for H-migration in dihydroxycarbene to fonn fonnic acid was shown to be less than 37 kcal mol-1 if an exchange with oxalic acid was involved (23). QRRK analysis of the pyrolytic decomposition of 2-chloro-l,l,l,2-tetrafluoroethane (F3CCFCIH) indicated that the primary route is a-climination of HC1 to form singlet F3CFC .34... 

Silylene SiH2 was directly detected during the pyrolytic decomposition of silane (and ethylsilane EtSiII3) for the first time by intracavity laser spectroscopy in 198865. The high detection sensitivity of this experiment allowed the pyrolysis mechanism to be examined under conditions that optimized film growth rather than spectroscopic conditions. 

A similar insertion reaction is possible with an Si—Si and an Si-C bond, which explains the formation of CH3SiD2SiH3 from the reaction of Si2D6 with me-thylsilane. Because it is easy to form silylene by a pyrolytic decomposition of silane, other similar reactions can be expected to be discovered in the future. 

Using uniform and straight nanochannels of an anodic aluminum oxide (AAO) film as a template, CNTs can be prepared by pyrolytic carbon deposition on the AAO film [109-116]. Briefly, the AAO film was subjected to carbon deposition from the pyrolytic decomposition of propylene at 800°C, which resulted in a uniform pyrolytic carbon coating on the inner wall of the template nanochannels. Then, the AAO template was removed with HF washing, and only carbon was left as an insoluble fraction. The formation process of carbon tubes using this chemical vapor deposition (CVD) technique is illustrated in Figure 3.8. 

The shock tube technique employed in the pyrolytic decomposition of polyfluorohydro-carbons22,27,28 showed that the elimination of molecular hydrogen fluoride is the predominant reaction. Yet, a side process of C—C bond breaking becomes important as the temperature is increased beyond 1300 K. Several fluoroethanes have been found to react by molecular dehydrofluorination in chemical activation process29 and Table 2 summarizes the kinetic parameters for the gas-phase pyrolysis of this type of compound. In the case of 1,1,2-trifluoroethane, three olefin products were obtained (equations 3-5). 

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