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Dichloroethane, decomposition

BrCHi CHjBr. A colourless liquid with a sweet odour, m.p. 10°C, b.p. 132°C. Manufactured by passing ethene through bromine or bromine and water at about 20 C. Chemical properties similar to those of 1,2-dichloroethane when heated with alkali hydroxides, vinyl bromide is formed. Used extensively in petrols to combine with the lead formed by the decomposition of lead tetraethyl, as a fumigant for stored products and as a nematocide. [Pg.134]

Oxychlorination of Ethylene or Dichloroethane. Ethylene or dichloroethane can be chlorinated to a mixture of tetrachoroethylene and trichloroethylene in the presence of oxygen and catalysts. The reaction is carried out in a fluidized-bed reactor at 425°C and 138—207 kPa (20—30 psi). The most common catalysts ate mixtures of potassium and cupric chlorides. Conversion to chlotocatbons ranges from 85—90%, with 10—15% lost as carbon monoxide and carbon dioxide (24). Temperature control is critical. Below 425°C, tetrachloroethane becomes the dominant product, 57.3 wt % of cmde product at 330°C (30). Above 480°C, excessive burning and decomposition reactions occur. Product ratios can be controlled but less readily than in the chlorination process. Reaction vessels must be constmcted of corrosion-resistant alloys. [Pg.24]

The reaction is carried out over a supported metallic silver catalyst at 250—300°C and 1—2 MPa (10—20 bar). A few parts per million (ppm) of 1,2-dichloroethane are added to the ethylene to inhibit further oxidation to carbon dioxide and water. This results ia chlorine generation, which deactivates the surface of the catalyst. Chem Systems of the United States has developed a process that produces ethylene glycol monoacetate as an iatermediate, which on thermal decomposition yields ethylene oxide [75-21-8]. [Pg.433]

Whereas cycHzation of the cu-keto-co -hydroxyamide 1466 in boihng toluene or xylene in the presence of camphorsulfonic acid (CSA) results in decomposition of the starting material 1466, heating of 1466 with excess TMSOTf 20 and N-methyl-morphoHne in 1,2-dichloroethane affords 46% of the desired cycHzation product 1467 [30] (Scheme 9.16). The close relationship of product 1467 to d -oxazolines suggests that reaction of carboxylic acids 11 with free (or C-substituted) ethanola-mines 1468 and HMDS 2/TCS 14 might lead analogously, via the silylated intermediates 1469, to d -oxazolines 1470 and HMDSO 7. As demonstrated in the somewhat related cyclization of 1466 to 1467, combination of TMSOTf 20 with N-... [Pg.223]

Homogeneous gas phase reactors will always be operated continuously whereas liquid phase reactors may be batch or continuous. Tubular (pipe-line) reactors are normally used for homogeneous gas-phase reactions for example, in the thermal cracking of petroleum crude oil fractions to ethylene, and the thermal decomposition of dichloroethane to vinyl chloride. Both tubular and stirred tank reactors are used for homogeneous liquid-phase reactions. [Pg.484]

For convenient preparation and workup of larger amounts of biphenylene, several runs can be combined after the decomposition of the benzenediazonium-2-carboxylate. Thus the submitters obtained 19.1 g. (25%) of air-dried biphenylene by combining four batches. They found that the use of larger amounts of 1,2-dichloroethane resulted in a moderate increase in yield by combining four batches, each prepared in 2.75 1. of 1,2-dichloroethane in a 4-1. beaker, they obtained 22.8 g. (30%) of product. [Pg.9]

So far only a few quantitative data on the thermodynamic stability of arenediazonium salts and crown ethers have been reported. Bartsch et al. (1976) calculated the value of the association constant of the complex of 18-crown-6 and 4-t-butylbenzenediazonium tetrafluoroborate from kinetic data on the thermal decomposition of the complex, Kt = 1.56 x 105 1 mol-1 in 1,2-dichloroethane at 50°C. Compared with the corresponding linear polyether this is at least a factor of 30 higher (Bartsch and Juri, 1979). [Pg.419]

The thermal decomposition of arenediazonium tetrafluoroborates is slowed down when the salt is complexed by 18-crown-6 (Bartsch et al., 1976). The kinetic data obtained for the 4-t-butylbenzenediazonium salt at 50°C in 1,2-dichloroethane revealed that the rate of complexed to uncomplexed salt is more than 100. Other crown ethers such as dibenzo-18-crown-6 and dicyclohexyl-18-crown-6 exhibited the same effect but smaller molecules such as 15-crown-5 did not influence the rate at all. It is not only the rate of the Schiemann reaction that is affected by the crown ether nucleophilic aromatic substitutions by halide ions (Cl-, Br-) at the 4-positions in arenediazonium salts are retarded or even entirely inhibited when 18-crown-6 is added. This is attributed to the attenuation of the positive charge at the diazonio group in the complex (Gokel et al., 1977). [Pg.420]

Juri and Bartsch (1979) have studied the coupling of 4-t-butylbenzene-diazonium tetrafluoroborate with N,N-dimethylaniline in 1,2-dichloroethane solution. The addition of one equivalent (based on diazonium salt) of 18-crown-6 caused the rate constant to drop by a factor of 10, indicating that complexed diazonium is less reactive than the free cation. Benzenediazonium tetrafluoroborate complexes of crown ethers are photochemically more stable than the free salt. The decomposition into fluorobenzene and boron trifluoride is strongly inhibited but no explanation has been given (Bartsch et al., 1977). [Pg.420]

There are a few reports of poly(naphthalene) thin films. Yoshino and co-workers. used electrochemical polymerization to obtain poly(2,6-naphthalene) film from a solution of naphthalene and nitrobenzene with a composite electrolyte of copper(II) chloride and lithium hexafluoroarsenate. Zotti and co-workers prepared poly( 1,4-naphthalene) film by anionic coupling of naphthalene on. platinum or glassy carbon electrodes with tetrabutylammonium tetrafluoroborate as an electrolyte in anhydrous acetonitrile and 1,2-dichloroethane. Recently, Hara and Toshima prepared a purple-colored poly( 1,4-naphthalene) film by electrochemical polymerization of naphthalene using a mixed electrolyte of aluminum chloride and cuprous chloride. Although the film was contaminated with the electrolyte, the polymer had very high thermal stability (decomposition temperature of 546°C). The only catalyst-free poly(naphthalene) which utilized a unique chemistry, Bergman s cycloaromatization, was obtained by Tour and co-workers recently (vide infra). [Pg.295]

Note 1,2-Dichloroethane may contain alkylamines (0.1 wt %) to inhibit decomposition during storage. [Pg.413]

Another synthetic approach to the octahedral complexes of type (252) is provided by the thermal decomposition of the hydrido complex [ReH7(PPh3)2] in the presence of 2-mercapto-quinoline or 2-hydroxyquinoline in 1,2-dichloroethane solutions. The solvent is source of the chloro ligands and, thus, essential for the formation of the rhenium(III) products. Comparable reactions in THF afford hydridorhenium(V) complexes (see Section 5.3.2.11). [Pg.347]

We are at a loss to explain the discrepancy in the BF3 enthalpies of interaction with the sulfur donors. Steric effects may be operative, but this is far from the whole story for the BCI3 interaction is much larger than BF3 with these donors. Furthermore, using the tentative ( 113)3 parameters to estimate those of ( 2115)3 , we calculate an enthalpy from E and of 11.1 k.cal mole- for the BF3-P( 2H6)3 adduct compared to a measured value of 9.5 k.cal mole i. The authors report much difficulty with the sulfur donor system, but their error estimates could not possibly account for the difference between our calculated and the observed result. The behavior of ( 2115)35 compared to ( 2115)3 is clearly inconsistent with the behavior of these two donors toward ( 2H5)sAl where both enthalpies are correctly predicted with our parameters. It may be that the BF3-( 2115)25 system has an even lower equilibrium constant than reported and is completely dissociated over the temperature range studied. (This would require a very different entropy if the — AH predicted by E and were correct.) A slight impurity (reported to be less than 0.1%) or decomposition product could interact appreciably with BF3 and changing pressure contributions from this adduct with temperature could be attributed incorrectly to the sulfur donor adduct. The actual BF3-sulfur donor adduct would then be a very common example of an adduct which cannot be studied by the vapor pressure technique because it is completely dissociated at the temperatures at which one of the components has appreciable vapor pressure. We have examined the reaction of BF3 ( 2Hs) 2O with large excess of ( H2) 4S in dichloroethane solution at 25 ° and have found the equilibrium constant to be too low to be measured calorimetrically. [Pg.113]

Some examples of the behavior of unsaturated ketonucleosides under alkaline conditions have also been reported. The enol acetate 61a is more stable than the parent ketonucleoside 36a. In 0.1 M methanolic sodium hydroxide, free theophylline was detected only after 4 h, by which time, loss of the acetyl group was complete a reaction time of more than 18 h was needed for complete cleavage of the glycosylic bond.51 In alcoholic solution, the unsaturated 4 -ketonucleoside 66 was very sensitive to nucleophilic attack, and decomposed rapidly, with elimination of the nitrogenous base.31 Thus, treatment with sodium borohydride at — 70° led to complete decomposition within 10 min but, when sodium borohydride was added to a solution of 66 in 1,2-dichloroethane containing acetic acid, fast reduction occurred, and no degradation was observed.31... [Pg.248]

CuCl-catalyzed decomposition of iodonium ylides prepared from /3-keto esters and diacetoxyiodobenzene, has been developed (equation 151)331. 1-Methylbenzvalene is obtained in a good yield by treating a mixture of lithium cyclopentadienide and 1,1-dichloroethane with butyllithium332. The tandem cyclization substitution in l-selenyl-5-hexenyllithiums derived from corresponding selenacetals via selenium/lithium exchange produces bicyclo[3.1.0]hexane derivatives333. [Pg.308]

Volatile organic compounds (VOCs), especially trihalomethanes, are frequently found in drinking water due to the chlorination of humic acids. When UV irradiation is applied to the pre-ozonation of humic acids, the decomposition of VOC precursors increases (Hayashi et al., 1993). The ozonation rates of compounds such as trichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, 1,2-dichloroethane, and 1,2-dichloropropane were found to be dependent on UV intensity and ozone concentration in the aqueous phase by Kusakabe et al. (1991), who reported a linear relationship between the logarithmic value of [C]/[C0] and [03]f for 1,1,1-trichloroethane, trichloroethylene, and tetrachloroethylene. The other two organochlorines followed the same first-order kinetics with and without UV irradiation (Kusakabe et al., 1991). Thus, the decomposition rate can be expressed as ... [Pg.310]

For several weeks these two dichlorides decomposed at the same rate by the unimolecular mechanism. But one day, without warning, the ethylene dichloride started to decompose much faster than the 1,1-dichloroethane, such that I could obtain the same conversion at 100 °C lower temperature. After reflection, I realized that the ethylene dichloride used had been recovered from the dry ice trap and then redistilled before use. Normally the 1,1- and 1,2-dichloroethanes were purified by careful fractional distillation. Clearly, my recovered sample contained a catalyst, or lacked an inhibitor. The latter seemed more probable, so I treated the 1,2-dichloroethane with chromic acid or potassium permanganate, shaking overnight. After redistillation, the purified dichloride still gave variable results, some days decomposing very fast and some not. The simply distilled material always had a constant rate of decomposition. The rate for 1,1-dichloroethane was always constant and independent of comparable chemical treatment. [Pg.2]

Finally, I identified another factor, a variable air leak. When I eliminated this, both dichloroethanes decomposed slowly by the unimolecular mechanism. When I let in a controlled flow of air (or chlorine), the 1,2-dichloroethane (in contrast to the 1,1-isomer) now decomposed rapidly at a much lower temperature. I had discovered my first new reaction the radical chain decomposition of the dichloride as in Scheme 2. [Pg.3]

The silylation of amino acids with BSTFA was studied in detail by Gehrke and coworkers [254—256]. BSTFA—acetonitrile (1 1) was applied first and fourteen amino acids were silylated at 135°C for 15 min. Glu, Arg, Lys, Trp, His and Cys, however, require up to 4 h, in order for measurable peaks to be obtained in the chromatogram. Despite such a long reaction, Gly and Glu gave two peaks and also it was difficult to separate the tris-TMS derivative of Gly from the derivatives of lie and Pro. The influence of polar and non-polar solvents was demonstrated later and was decisive mainly with respect to uniformity of the products. Only the bis-TMS derivative was produced in hexane, methylene chloride, chloroform and 1,2-dichloroethane bis- and tris-derivatives were produced in six more polar solvents. On the other hand, Arg did not provide any peak in the less polar solvents that were used and only one peak in the six more polar solvents. The best and most reproducible results were obtained when silylating seventeen amino acids with BSTFA—acetonitrile (1 1) at 150°C for 15 min 2.5 h at 150°C were necessary for the reproducible derivatization of Gly, Arg, and Glu. These reaction conditions were recommended for the analysis of all twenty amino acids. The TMS derivatives of amino acids were found to be stable on storing them in a sealed vial at room temperature for 8 days, with no decomposition. [Pg.138]

The course of trialkylaluminum-induced cyclization of unsaturated aldehydes was reported to be profoundly influenced by the solvent and temperature. For instance, unimolecular decomposition of the 1 1 complex of citronellal-MesAl at -78 °C to room temperature afforded the acyclic compound 42 in hexane, whereas isopregol (43) was obtained exclusively in 1,2-dichloroethane. Moreover, the cyclization-methy-lation product 44 was formed with high selectivity by use of excess MesAl in CH2CI2 at low temperature (Sch. 24) [48]. [Pg.205]

Yates and Hughes photochemically stimulated the radical-chain decomposition of 1,2-dichloroethane to vinyl chloride and hydrogen chloride. They obtained an overall activation energy of 12.5 kcal.mole from which they deduced an activation energy of 23.0 kcal.mole" for the step... [Pg.194]

The mercury resonance line at X 2537 A, corresponding to the transition 6(3Pi) 6(1 So), has been used in most studies and monoisotopic photosensitisation has been specifically employed to examine the possible isotopic enrichment of the mercury compounds produced in these reactions. Thus, in the Hg monoisotopic photosensitised decomposition of methyl chloride " - the main products are methane, ethane, dichloroethane and hydrogen chloride together with calomel enriched with the ° Hg isotope. The following mechanism has been proposed " for the decomposition... [Pg.201]

The decompositions were carried out in a 50 ml thermostated glass flask equipped with a condenser and magnetic stirrer. Typically a solution of cyclohexenyl hydroperoxide (2 mmol), n-decane (internal standard) and catalyst (0.02 mmol metal) were stirred (1000 rpm) in 10 ml chlorobenzene at 80 °C for 5 h. The cyclohexenyl hydroperoxide conversion was determined by iodometric titration. Typically, 3.0 g of reaction mixture was diluted with 30 ml acetic acid/chloroform (2 1 v/v), 2.5 ml of saturated aqueous KI solution was added and the solution was allowed to stand for 1 h in fhe dark before adding 50 ml of deionized wafer and titration with a 0.1 M sodium thiosulfate solution. The reaction products were analysed by GC (CP Sil 5 CB column) after destroying remaining cyclohexenyl hydroperoxide by the addition of an excess of triphenylphosphine as a solution in 1,2-dichloroethane (24 g / 1). [Pg.706]

Besides the synthesis of 1-chloroalkyl carbonates, this method is general enough to be used for the preparation of 1-fluoroalkyl, 1-bromoalkyl or 1-iodoalkylcarbonates as shown in table 3-7. However, the method gives poor results or even failed when the haloformate is too unstable in presence of the catalyst (see section 3-2-1). For example, attempts to prepare 1-chloroethyl ethyl carbonate (CEEC) itself in 1,2 dichloroethane at 60°C with 0.05 equ. pyridine, gave almost total decomposition of ethyl chloro-formate. [Pg.133]


See other pages where Dichloroethane, decomposition is mentioned: [Pg.499]    [Pg.499]    [Pg.184]    [Pg.80]    [Pg.366]    [Pg.219]    [Pg.540]    [Pg.295]    [Pg.479]    [Pg.181]    [Pg.423]    [Pg.246]    [Pg.423]    [Pg.724]    [Pg.300]    [Pg.266]    [Pg.146]    [Pg.289]    [Pg.238]    [Pg.211]   
See also in sourсe #XX -- [ Pg.2 , Pg.5 , Pg.99 ]




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1,2-dichloroethane

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