Toluene decomposition product

Hydroxyl elimination is necessary for the formation of benzaldehyde and benzoic acid derivatives and, ultimately, benzene and toluene (Fig. 7.46).2 It is proposed that a cleavage between the hydroxyl group and aromatic ring leads to benzenoid species which undergo further cleavage coupled with oxidation to give various decomposition products. 

Typical characterization of the thermal conversion process for a given molecular precursor involves the use of thermogravimetric analysis (TGA) to obtain ceramic yields, and solution NMR spectroscopy to identify soluble decomposition products. Analyses of the volatile species given off during solid phase decompositions have also been employed. The thermal conversions of complexes containing M - 0Si(0 Bu)3 and M - 02P(0 Bu)2 moieties invariably proceed via ehmination of isobutylene and the formation of M - O - Si - OH and M - O - P - OH linkages that immediately imdergo condensation processes (via ehmination of H2O), with subsequent formation of insoluble multi-component oxide materials. For example, thermolysis of Zr[OSi(O Bu)3]4 in toluene at 413 K results in ehmination of 12 equiv of isobutylene and formation of a transparent gel [67,68]. 

Catalyst systems of the type [NiL X + AlEt Xj (where L = PR and X = halide) afford highly active catalysts for olefm dimerisation. However, when complex 11 (Scheme 13.8) is treated with AlEt Cl in the presence of 1-butene, in toluene at 20°C the only products observed were decomposition products, 12,13,14 no butene dimers were obtained [22], At low temperatures (-15°C) and using the complex with 1,3-diiso-propylimidazolin-2-ylidene as the NHC ligand, small amounts of butene dimers were observed. It is apparent from these results that Ni-NHC complexes are capable of olefin dimerisation, however, decomposition of the catalyst via reductive elimination predominates. 

It has been suggested however that isotacticity derives from polymerization occurring on colloidal particles formed by thermal decomposition of the catalysts. As stated previously, in the presence of the monomer even the allyl compounds are stable at 65°C and none of the thermal decomposition products (black to yellow solids) could be detected. As a check on these results a polymerization of propylene was carried out with Zr (benzyl) 4 in toluene at 0°C in a sealed tube. The reaction was very slow and analytical quantities of polymer could be obtained only after 312 hr. NMR analysis showed peaks assignable to isotactic sequences, and these were much stronger than the peaks assignable to syndiotactic diads. It was concluded... 

Analytical identification of monoazo colorants and the other decomposition products requires effective (analytical) methods of concentration, which is made possible by high performance liquid chromatography (HPLC). Prior to HPLC analysis, the pigmented medium was extracted for 20 hours with toluene in a soxhlet extractor. These analytical methods also showed that above 240°C, especially after prolonged exposure of the pigmented polymer material to heat, dichlorobenzidine (DCB) is also formed. 

The low temperature form of the triphosphate, Na6P30io(II), is formed with the loss of residual water from the mixture of decomposition products by raising the temperature to 130-150°C. Direct dehydration to NaBP30io(II) also occurs, partially at least, by simply and directly heating the hexahydrate in vacuum or in boiling toluene (110.8°C) (266, 372). 

Displaying a grasp of chemistry remarkable even among chemical engineers, the authors ascribe the hazardous side reaction consequent upon mono-nitration of toluene in mixed acid, to a decomposition of nitric acid (science has hitherto regarded nitric acid as thermodynamically more stable than conceivable decomposition products). This is favoured by poor mixing in what they describe as a three phase mixture (m/xo-nitrotoluenes being apparently immiscible with toluene). What the calorimetric study described seems to have observed is the transition from nitration to oxidation of the substrate. 

Benzothiophene experiments conducted at 375°C for 30 minutes with KCl-NaOH mixtures (70 30 by wt) resulted in no decomposition or desulfurization. Experiments conducted with K2C09-Na0H mixtures (70 30 by wt) resulted in complete decomposition of benzothiophene, yielding o-thiocresol and toluene as products. Relative amounts of the two products were similar to those found in experiments that used the KOH-NaOH mixture. Experiments with the KCl-NaOH mixture were repeated at longer reaction times (1 and 3 hours). After 1 hour, very little decomposition of benzothiophene had occurred. After 3-hour reaction times, the majority of benzothiophene had decomposed to toluene (4>), o-thiocresol (26 ), and tolyldisulfide (23>). While the yield of tolyldisulfide (an oxidation product of o-thiocresol) was somewhat unexpected, the longer reaction times demonstrate that KCl-NaOH mixtures can cause benzothiophene decomposition. Again, the induction or inhibition period may account for the lack of KCl-NaOH reactivity using 30-minute reaction times. 

Significant amounts of several carotenoid decomposition products were also identified in this study. Toluene, a-ionone and B-ionone are well-known decomposition products of carotenoids. In corn grain, the two most abundant carotenoids are lutein and phytoene (10). The formation of isophorone from lutein by a free radical mechanism was reported in an earlier publication (4), and phytoene... 

Thermal degradation of foams is not different from that of the solid polymer, except in that the foam structure imparts superior thermal insulation properties, so that the decomposition of the foam will be slower than that of the solid polymer. Almost every plastic can be produced with a foam structure, but only a few are commercially significant. Of these flexible and rigid polyurethane (PU) foams, those which have urethane links in the polymer chain are the most important. The thermal decomposition products of PU will depend on its composition that can be chemically complex due to the wide range of starting materials and combinations, which can be used to produce them and their required properties. Basically, these involve the reaction between isocyanates, such as toluene 2,4- and 2,6-diisocyanate (TDI) or diphenylmethane 4,3-diisocyanate (MDI), and polyols. If the requirement is for greater heat stability and reduced brittleness, then MDI is favored over TDI. 

Ti-MOR promoted the ring hydroxylation of toluene, ethylbenzene and xylenes with negligible oxidation of the ethyl side chain [59]. In the same study, however, and in contrast to earlier ones, a similar result was also reported for TS-1. No oxidation of benzylic methyls was observed. Cumene yielded mainly the decomposition products of cumyl hydroperoxide. The oxidation of t-butylbenzene was negligibly low. The reachvity order, toluene > benzene > ethylbenzene > cumene, reflects the reduced steric constraints in the large pores of mordenite. Accordingly, the rate of hydroxylation ofxylene isomers increased in the order para < ortho < meta, in contrast to the sterically controlled one, ortho < meta para, shown on TS-1. It is worth menhoning that the least hindered p-xylene exhibited the same reactivity on either catalyst. 

The photodecomposition of benzylamine has recently been investigated. Terenin et reported that the major decomposition products, as analyzed by kinetic mass spectroscopy, are H + PhCH2NH, with only a trace of the species NHj and PhCH2. However, irradiation of A -methylbenzylamine or A, A -dimethylbenzyl-amine in ether, yields toluene (f> = 0.085) and dibenzyl, presumably via C-N cleavage the effective radiation was about 2700 The photodecomposition of A-methyl-l,l-diphenylmethylamine and other derivatives also proceeds via C-N cleavage since the major product is diphenylmethane varying amounts of 1,1,2,2-tetraphenylethane were also detected, depending on the solvent viscosity, viz. 

The bromide is prepared in the same way as the chloride, is insoluble in organic solvents, and melts at 251 C, It reacts "with alkaline sodium stannite solution, yielding a brick-red compound I., which turns brown on exposure to iightl This decomposition product when extracted with hot benzene gives II., the corresponding mercuric compound to I. It melts at 190° C., is insoluble in water, alkalies, dilute acids, or acetone, readily soluble in benzene or toluene, and is decomposed by concentrated liydrochloric acid. With mercuric chloride or picric acid it gives precipitates, but remains unchanged when boiled with potassium hydroxide, cyanide, or iodide. 

The further oxidation of benzaldehyde to benzoic acid is complicated also by the numerous condensations and polymerizations that occur. At 350° C. benzaldehyde decomposes to benzyl benzoate with the formation of some benzene and carbon monoxide.128 At the same temperature benzyl benzoate decomposes to benzoic anhydride, toluene, and benzalde-hyde. At temperatures of 700° C. carbon monoxide and benzene are the chief decomposition products of benzaldehyde and some diphenyl and triphenyl also form. In the presence of catalysts aud oxygen further reactions lead to the formation of complicated gums and tars which involve losses, make separation of the product difficult and effectively destroy the activity of the catalyst by coating it over. 

Enormous quantities of coal are subjected to destructive distillation to obtain its numerous and valuable decomposition products, of which gas, tar, ammonia and its salts, coke, and gas carbon are made on a huge scale and all consumed. The gas provides light and heat, whilst the tar, useful in many ways in the crude state, gives, when distilled, benzene, toluene, solvent naphtha, carbolic acids, naphathalene, anthracene, and many other substances, which in their turn yield, in the hands of the technologist, a host of further useful bodies, including explosives, dyes, disinfectants, and drugs. Pitch, the residue of tar distillation, is... 

Both freshly metalated TMED and aged product contain an active Li-CH2N structure shown by ethylene polymerization activity and trans-metalation reactions. For example metalated TMED reacts slowly with toluene to produce TMED LiCH2. Hydrogenation of 0.5M TMED LiBu complex in n-heptane aged one week at 25 °C gave an 82% recovery of TMED and 18% decomposition products. These experiments also demonstrated that the rearrangement observed by NMR did not involve the skeletal structure of TMED. 

Other phosphonmm salts which may be obtained from the chloride in the usual manner are as follows, the compounds in brackets being the decomposition products formed when the salts are heated to a high temperature bromide (almost totally decomposed only resembles the chloride to a slight extent) hydroxide (triethylphosphine oxide, toluene), carbonate and acid carbonate (triethylphosphine oxide, toluene, carbon dioxide) sulphate (2 mols. trietfylphosphine oxide, stilbene, carbon dioxide) acetate (triethylphosphine oxide and methyl tolyl ketone, and to a smaller extent triethylphosphine and the methyl ester of toluic acid) oxalate (triethylphosphine oxide, toluene, carbon monoxide, carbon dioxide). 

The energy of activation for isomerization of norbornadiene itself is considerably largeThe reaction is mechanistically complex, and yields toluene and decomposition products as well as cycloheptatriene. Under the conditions used, part of the toluene is formed by isomerization of the cyclo-heptatriene , possibly via norcaradiene. In the gas phase the energy of activation for formation of cycloheptatriene from norbornadiene is about 51 kcal.mole and log is about 14.8 (refs. 24, 190). Activation parameters for the formation of toluene directly from norbornadiene in the gas phase are Ecf = 53 kcal.mole and log A — 14.2. These reactions probably involve initial cleavage of the C-1, C-7 bond in norbornadiene to yield an allylic diradical which can cyclize to norcaradiene (a precursor for both cycloheptatriene and toluene) as well as undergo other reactions. 

The dry crude product can be used immediately for the preparation of Fe(N03)(CO)3. However, there may arise a need to purify it, especially to remove excess nitrite and decomposition products. In this case, the crude product is extracted (in the absence of air and light) in a Soxhlet apparatus with 200 ml. of ether until the reflux is colorless. Evaporation of the extract under reduced pressure yields a bright-orange mass. Addition of toluene or xylene to the ether solution gives the salt as fine crystals. Yield 60 g. of crude product, which on careful workup yields 45 g. of pure substance. 

There is a rich literature associated with studies of the breakdown or formation of specific chemical compounds and classes of chemical componnds during burning processes. A study of the thermal decomposition of pentachlorobenzene, hexachlo-robenzene, and octachlorostyrene in air contained many such citations. In this study, nearly pure 10- to 20-mg samples of the cited chemicals were decomposed in a vertical combustion furnace and the decomposition product trapped on cooled X AD-4 resin followed by charcoal tubes. The adsorbed components were desorbed with toluene and analyzed using capillary GC and GC/MS. The decomposition products formed depended upon the applied temperature, the oxygen concentration, and the residence time in the hot zone of the combustion chamber. 

---