Chloroformates, pyrolysis

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6]-, 1,1-dichloroethane cis- and /n j -l,2-dichloroethylenes [156-59-2 and 156-60-5]-, 1,1-dichloroethylene [75-35-4] (vinyhdene chloride) 2-chloroethanol [107-07-3]-, ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5])-, and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of soflds which can foul and clog operating lines and controls (78). 

By-products from EDC pyrolysis typically include acetjiene, ethylene, methyl chloride, ethyl chloride, 1,3-butadiene, vinylacetylene, benzene, chloroprene, vinyUdene chloride, 1,1-dichloroethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane [71-55-6] and other chlorinated hydrocarbons (78). Most of these impurities remain with the unconverted EDC, and are subsequendy removed in EDC purification as light and heavy ends. The lightest compounds, ethylene and acetylene, are taken off with the HCl and end up in the oxychlorination reactor feed. The acetylene can be selectively hydrogenated to ethylene. The compounds that have boiling points near that of vinyl chloride, ie, methyl chloride and 1,3-butadiene, will codistiU with the vinyl chloride product. Chlorine or carbon tetrachloride addition to the pyrolysis reactor feed has been used to suppress methyl chloride formation, whereas 1,3-butadiene, which interferes with PVC polymerization, can be removed by treatment with chlorine or HCl, or by selective hydrogenation. 

Flash vapor pyrolysis of chloroform has been used to effect the... 

Several experimental studies on S-MMA copolymcrization have appeared all suggest predominant combination.181" 83 Ohtani el al.m analyzed the end groups of PSMMA (60°C, AIBN, chloroform) by pyrolysis-gas chromatography to find values for the number of end groups per molecule of between 1.56-1.77 (increasing with polymer M ) which corresponds lo ail overall kjkw of between 0.39 and 0.21. Estimation of kjktc for cross termination requires knowledge of the... 

A number of other symmetric dichalogeno carbamates have been employed in, for example, the deposition of ZnS by a dip-dry method186 from a chloroform solution containing an equimolar mixture of [Zn(S2CNBu2)2] and the thiolate compound [EtZn(SPr )]. Pyrolysis was carried out at 300 °C under N2 and the polycrystalline (cubic phase) films were free from oxide contamination. 

Wentrup and co-workers investigated the flash vacuum pyrolysis of isopropylidene (l-methyIpyrrolidin-2-ylidene)malonate (1261) (86CC369) (Scheme 51). When the pyrolysis was carried out at 450°C (10-4 torr, contact time 10 3 sec), and the product was condensed on a cold finger at -196°C, (pyrrolidinylidene)malonic anhydride (1262) could be identified. Malonic anhydride (1262) in chloroform solution at -20°C lost carbon dioxide to give methyleneketene (1263), which was reacted with a few drops of water or methanol to yield acrylates (1264). Flash vacuum pyrolysis of 1261 at higher temperature (800°C) gave pyrrolopyrrolone (1265). The products were characterized by IR and 13C-NMR data. 

Primary Conversions and Influence of Mobile Phase Yields for the various H-donor and non-donor solvent extractions of Linby coal at 400% are summarised in Table III the conversions for the THF-extracted coal include the extracted material. Surprisingly, pre-extraction with THF significantly increases primary conversions in the polynuclear aromatic compounds (PACs) investigated. These findings appear to be contrary to those of other liquefaction (16) and pyrolysis (17) studies where prior removal of chloroform-extractable material significantly reduced conversions. However, Rincon and Cruz (18) have reported recently that pre-swelling coals in THF increases conversions for both anthracene oil and tetralin. The fact that Point of Ayr (87% dmmf C) coal yielded over 80% pyridine-solubles in pyrene (C.E. Snape, unpublished data) without pre-extraction is consistent with the earlier results of Qarke et al (19) for anthracene oil extraction where UK coals... 

Vapor phase pyrolysis of 2-aminobiphenyl in chloroform at 350°C produces carbazole,as does heating at 500-800°C in a high-frequency glow discharge at 25-34 A small amount (11%) of carbazole 280 was formed during the reaction of 281 with copper-potassium carbonate and 1-iodo-naphthalene in nitrobenzene. ... 

Cyclopentanoindole on vapor-phase pyrolysis in chloroform gave carbazole, 3-chlorocarbazole, and 4-chlorocarbazole (28 59 13) in 24% overall yield. ... 

In the case of rhodium, however, it was demonstrated early that in the synthesis of [Rh6C(CO)l5]2 the encapsulated carbon atom originated as chloroform, which had reacted with the rhodium carbonyl anion [Rh7(CO)l6]3- (59). In the cobalt analog, [Co6C(CO)l5]2-, the carbon atom is derived indirectly from carbon tetrachloride [via Co3(CO)9CCl] (60) Both these syntheses are performed under mild conditions, and there are apparently no examples of carbidocarbonyl clusters of cobalt or rhodium prepared directly from the metal carbonyls under pyrolysis conditions. 

The eastern Oklahoma coals were obtained from the Oklahoma Geological Survey Organic Petrography Laboratory where they had been crushed to -20 mesh and analysed on an as received basis (Table I). The whole, crushed coals were extracted for 48 hours with a 1 1 (v/v) mixture of chloroform/methanol using a soxhlet apparatus. Exhaustive extraction ensures that soluble compounds are removed and that the compounds produced during pyrolysis are derived from the organic matrix of the coal. 

A property seemingly unique to microwave chemistry is that the individual phases in multi-phase systems can be heated at different rates owing to differences in the dielectric properties. In some cases, a sizeable temperature difference can be maintained for several minutes. This technique has been applied usefully to produce aryl vinyl ketones batchwise by Hofmann elimination in a two-phase system comprising water and chloroform [77]. Although reactions took place in the aqueous phase, the thermally unstable products simultaneously were extracted and diluted into the cooler organic phase, which could be recycled. Yields were nearly quantitative and twice those obtained by traditional pyrolysis-distillation under vacuum. 

The first step is set up to produce hydrogen fluoride and the second yields trichlo-romethane (chloroform). Chloroform is then partially fluorinated with hydrogen fluoride to chlorodifluoromethane using antimony fluoride as catalyst in the third step. Finally, in the fourth step, chlorodifluoromethane is subjected to pyrolysis in which it is converted to tetrafluoroethylene. The pyrolysis is a noncatalytic gas-phase process carried out in a flow reactor at atmospheric or subatmospheric pressure and at temperatures 590 to 900°C (1094 to 1652°F) with yields as high as 95%. This last step is often conducted at the manufacturing site for PTFE because of the difficulty of handling the monomer.9... 

Pyrrolo 2,3-/ Ipyridine (75) underwent pyrolysis in chloroform to give a separable mixture of 1,8-naphthyridine (76, R=H) and 3-chloro-l,8-naphthyridine (76, R=C1) (vapor phase, 550°C low yields).1145... 

The use of selectivity data as a means of identifying intermediates has been employed effectively. For example, in the dichlorocyclo-propanation of olefins, the selectivity of attack using CC12 generated by different methods (the pyrolysis and a elimination of chloroform) was found to be almost identical (Skell and Cholod, 1969a). This was... 

Addition of aryl tellurium trihalides to cyclohexene produces trails-] -aryldihalotelluro-2-halocyclohexanes when the reactions are carried out in chloroform, and trans-1-aryldihalotelluro-2-methoxycyclohexanes when methanol is used as the reaction medium. Treatment of the 2-chlorocyclohexyl 4-methoxyphenyl tellurium dichloride with terf.-butyl hydroperoxide in acetic acid yielded tram-l,2-dichlorocyclohexane and aryl chloride. Bis[4-methoxyphenyl] tellurium dichloride did not yield any aryl chloride under these conditions1. Pyrolysis of tran.s-2-methoxycydohexyl phenyl tellurium dibromidc afforded Crum- l-bromo-2-methoxycyclohexane1. 

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