Dichlorobenzenes pyrolysis

However, bromobenzene and chloroaromatics (chlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene) are inert enough to be used routinely,131 181 222-223 except when the aryl cation generated during dediazoniation is stable enough to arylate the aromatic solvents.137 The advantage of pyrolysis in chlorobenzene over dry decomposition has been illustrated in the synthesis of mono- and difluorobenzo[c]phenanthrenes.230... 

The pronounced differences among the product distributions from the three dichlorobenzenes rule out any extensive scrambling of the chlorine atoms, such as was found for deuterium in deuteriated benzene at high temperatures. That such scrambling of chlorine atoms does not occur is indicated further by our failure to detect mono- and trichlorobenzenes among the pyrolysis products of the dichlorobenzenes alone under the same conditions. 

Pyrolysis products of chlorinated polyethylene contain molecules similar to those found in polyethylene pyrolysates and, in addition, compounds similar to that obtained from vinyl chloride (significant amount of HCI). Chlorosulfonated polyethylene typically contains only about 1.5% sulfur, but sulfur-containing compounds such as SO2 can be detected among its pyrolysis products. The distribution of chlorine atoms in chlorinated polyethylene has been investigated using Py-GC [55, 56]. The polymer was considered equivalent with a terpoiymer poly[ethylene-co-(vinyl chloride)-co-(1,2-dichloroethylene)]. The level of specific degradation products such as aromatic molecules (benzene + toluene + styrene + naphthalene), chlorobenzene, and dichlorobenzenes correlates well with the carbon/chlorine ratio in the polymer. 

If the ratio of chlorine to benzene materially exceeds 1 1, inflammation may occur at the mixing point, but a cyclic operation with recycle of lower chlorinated benzenes allows easy chlorination to tri- and tetrachloroben-zenes. There is little change in the ratio of mono- to dichlorobenzenes at temperature increases above 400 C, but above 500 C pyrolysis and condensation reactions occur, with the formation of carbon, hexachloroben-zene, and chlorinated biphenyls. 

This later position corresponds to the mtheninm maximum diffraction peak as shown by the XRD pattern in Fig. 7. We observed that, on the one hand, an interesting fact is that this pyrolysis in gas phase resembles the XRD results published years before for RuxSCy nanopowders synthesized after 20 h in a non-aqueous solvent, i.e., xylene or 1,2-dichlorobenzene. ... 

The pyrolysis or chemical vapor deposition of a metal precursor, a volatile complex such as FeCp2, CoCp2, or NiCp2, and a carbon source, such as acetylene, toluene, dichlorobenzene, or Cgo, also permits the simultaneous synthesis of CNTs and confined metal nanowires. Encapsulated nanowires of Fe [56,178-181], FeCo [69], and FeNi [182] within CNTs were synthesized using elevated temperatures. When [Co(CO)3NO] was used both as catalyst and the source for CNT growth, the nanowires and the filling yields were poor [183]. 

Benzene, chlorobenzene, dichlorobenzene and trichlorobenzene are four major products formed in the pyrolysis of vinylidene chloride/vinyl chloride copolymer. To make the composition calculation, the first assumption is that all trimer peak intensities generated from the Py-GC after correction for pyrolysis efficiency and detection efficiency accurately represent the triad distribution of the vinylidene chloride/vinyl chloride copolymer. If a close relationship exists between the triad distribution in the polymer chain and the production of trimers in pyrolysis, the composition and number average sequence length can be calculated on the basis of the trimer production in the pyrolysis. Results were in good agreement with those obtained by H-NMR (Table 4.11). Copolymers containing 11 wt% and 5 wt% vinyl chloride and 5% and 89% vinylidene chloride were successfully analysed. 

Where Kn is the combination of pyrolysis efficiency and detection efficiency. Because the trimers CCD, DCC, and CDC all form chlorobenzene, the second assumption must be made that Kn is the same for CCD, DCC, and CDC. The same assumption must be made for dichlorobenzene with the trimers of DDC, CDD, and DCD. The triad distribution in the polymer and the trimer peak intensities from pyrolysis can be written as ... 

B) Pyrolysis - gas chromatography of polyvinylidene chloride, (a) tetradichlorobenzene, (e) trichlorobutadiene, (0 chlorobenzene, (g) vinyldene-chloride. From Denig with permission. Carol Hauser Verlag Munich... 

The unique phenomenon in the pyrolysis of vinylidene chloride/vinyl chloride copolymer is the trimer formation. Under pyrolysis conditions, the polymer will directly undergo the thermal dehydrochlorination to form a conjugated polyene [205]. The polymer will then unzip, followed by a radical cyclisation to form benzene, chlorobenzene, dichlorobenzene, and trichlorobenzene. The mechanism can be expressed as ... 

Figure 1.2 (A) Filament pyrolysis - gas chromatogram of PVC (a) biphenyl, (b) methyl naphthalene, (c) naphthalene, (d) methylindene, (e) tetralin, (f) methyl indene, (g) indene, (h) indane, (i) styrene, (j) o-xylene, (k) ethylbenzene, (1) toluene, (m) benzene. (B) Filament pyrolysis - gas chromatography of polyvinylidene chloride, (a) tetra-chlorostyrene, (b) trichlorostyrene, (c) 1,3,5 trichlorobenzene, (d) w-dichlorobenzene, (e) trichlorobutadiene, (f) chlorobenzene, (g) vinyldene-chloride. [Source Author s own files)...

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