Diethyl pyrolysis

The only commercially important dialkyl sulfates are dimethyl sulfate and diethyl sulfate. Estimated worldwide production in 1996 for dimethyl sulfate was 90,000 metric tons per year. Dimethyl sulfate was initially made by vacuum pyrolysis of methyl hydrogen sulfate ... 

Dehydrocyanation of diethyl 4-cyano-2,7-dimethyl-4,5-dihydro-1 //-azepine-3,6-dicarboxylate (3, R = Et) occurs at 315-320 C to directly yield the 3//-azepine 4.29 The corresponding dimethyl ester, however, on pyrolysis at 262C yields the 4//-azepine 2, which on further heating in sand at 360 °C rearranges to the 3//-isomer 5. 

Cyclization of 1-ureidopyrroles 88 with a base gave (79JHC833) pyr-rolo[2,l-/][I,2,4]triazines 89. Pyrolysis of 89 (R2 = COOH) afforded 90. Compounds 88 were prepared by treating chloroacetone semicarbazone 85 with the sodium salts of diethyl oxalacetate or oxalylacetophenone 86 to give semicarbazones 87, which were converted to 88 by the action of hydrochloric acid (Scheme 22). 

Pyrolysis of diethyl aluminum azide [(C2H5)2A1N3] at 450-870°C). 

The pyrolysis of aluminum-nitrogen organic complexes, such as diethyl aluminum azide [(C2H5)2A1N3], is also used successfully at low deposition temperatures (450-870°C).0 l Another metallo-organic, hexakis(dimethylamido)dialuminum, reacting with ammonia allows deposition at 200-250°C at atmospheric pressure. 1... 

Pyrolysis of the phosphorodichloridothioate (59) at 550 °C gives mainly dibenzothiophen and a smaller amount of the cyclic phosphonochlorido-thioate (60). Thermal decomposition of di-t-butyl peroxide in triethyl phosphate gives rise to diethyl methyl phosphate in a reaction which may be interpreted as resulting from attack of methyl radical on the phosphoryl oxygen. An extension of this mechanism accounts for the formation of (61) from tri-isopropyl phosphate under the same conditions. 

Cyclohexadienylidenes, disubstituted at the 4-position are expected to be kinetically more stable than the parent carbene, however, the rearrangement to benzene derivatives is still very exothermic. The gas phase chemistry of 4,4-dimethyl-2,5-cyclohexadienylidene Is was investigated by Jones et al.100,101 The gas phase pyrolysis of the diazo compound 2s produces a mixture of p-xylene and toluene, and by crossover experiments it was demonstrated that the methyl group transfer occurs intermolecularly via free radicals. Thus, the pyrolysis of a mixture of the dimethyl and the diethyl derivative 2s and 2t... 

The pyrolysis of diethyl mercury has been studied using a nitrogen carrier flow system87 both in the presence and absence of toluene. The experimental conditions used were total pressure = 10+1 torr with 0.4 torr partial pressure of toluene, alkyl pressure 1-10 x 10 2 torr, decomposition 10-75 % and contact time 0.1-0.3 sec. The presence of toluene had no effect on the rate coefficient, the observed ethane/ethylene ratio ( 1) or the C4/C2 ratio ( 4). These ratios were essentially independent of temperature. 

The mechanism for the photolysis of diethyl mercury is identical to that for the pyrolysis88, 90. The reaction of C2H5 with diethyl mercury, which apparently was of no importance under the conditions used in the pyrolysis studies, is also insignificant over the temperature range 25-75 °C. The photolysis produces ethyl radicals which initially have about 31 kcal.mole-1 excess energy so that the C4/C2 ratio is dependent on the surface/volume ratio and on the total pressure in the system. At 25 °C with essentially thermalized radicals (200 torr Ne added) CJC2 20 while at 20 torr CJC2 3. 

The autocatalytic effect of lead on the rate of reactions (3) and (4) was demonstrated146 by comparing the pyrolysis of mixtures of tetramethyl lead and hexaethyldiplumbane and of hexaethyldiplumbane and diethyl lead in the presence and absence of lead formed by reaction (4). 

Reaction of l,3-bis(methylthio)-2-methoxypropane with 2 moles of lithium diisopropylamide5 (or w-butyllithium) effects (a) the elimination of methanol to form l,3-bis(methylthio)propene and (b) the lithiation of this propene to generate l,3-bis(methylthio)allyllithium in solution. Its conjugate acid, l,3-bis(methylthio)propene, can be regenerated by protonation with methanol, and has also been prepared (a) in 31% yield by reaction of methylthioacetaldehyde with the lithio derivative of diethyl methylthiomethylphosphonate,5 (b) in low yield by acid-catalyzed pyrolysis of l,l-bis(methylthio)-3-methoxypropane,6 and (c) in low yield by acid-catalyzed coupling of vinyl chloride with chloromethyl methyl sulfide.7... 

The presence of an acetoxy group is not a necessary condition for the methoxycarbonyl rearrangement. Thus, the pyrolysis of diene 334 (300-320 °C, 1 h, 97% conversion) gave the diester 335 as the major product (equation 119)174. Dicarboxylates like 334 were suggested to be the intermediates in pyrolysis (420 °C, flow system) of dimethyl and diethyl 2-acetoxycyclohex-3-ene 1,1-dicarboxylates175. 

Pyrolysis of diethyl phthalate in a flow reactor at 700 °C yielded the following products ethanol, ethylene, benzene, naphthalene, phthalic anhydride, and 2-phenylnaphthalene (Bove and Arrigo, 1985). 

Phenanthrene was analyzed directly by fluorescence with excitation at 365 nm and emission at 394 nm and quantified by comparison to a standard curve. 5-Chlorouracil was analyzed directly by absorbance at 270 nm. Attempts to determine 5-chlorouracil as the pyrolysis product of its tetramethylammonium salt (11) were unsuccessful. Hypochlorite was determined by the ferrous-N,N-diethyl-p-phenylenediamine titration method (12). 

CARBENE. The name quite generally used for the methylene radical, CH,. It is formed during a number of reactions. Thus the flash photochemical decomposition of ketene (CH2=C=0) has been shown to proceed in two stages. The first yields carbon monoxide and CHj. the latter then reacting with more ketene to form ethylene and carbon monoxide. Carbcne reacts by insertion into a C- H bond to form a C-CH, bond. Thus carbene generated from ketene reacts with propane to form, i-butane and isobutane. Carbene generated by pyrolysis uf diazomethane reacts with diethyl ether to form ethylpropyl ether and ethylisopropyl ether. 

Isoxazoline-3,5-dicarboxylic acid, 4-oxo-diethyl ester synthesis, 6, 106 Isoxazoline-4,5-dione, 3-methyI-4-oxime pyrolysis, 6, 42 Isoxazolines... 

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