Organomercury compounds. XIV. The preparations of bispolychlorophenylmercury compounds by mercuration reactions

1972 ◽  
Vol 25 (8) ◽  
pp. 1645 ◽  
Author(s):  
RJ Bertino ◽  
GB Deacon ◽  
FB Taylor
Keyword(s):  
Thermal Decomposition ◽  
Elevated Temperatures ◽  
Organomercury Compounds

The bispolychlorophenylmercurials R2Hg (R = C6Cl5 2,3,4,5-Cl4H, 2,3,4,6- Cl4C6H 2,3,5,6-C14C6H, 2,3,4-Cl3C6H2, 2,4,6-Cl2C6H2, and 2,5-Cl2C6H3) have been prepared by direct mercuration of pentachlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3,5-tetrachlorobenzene, 1,2,4,5-tetraohlorobenzene, 1,2,3-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4-dichlorobenzene respectively, with mercuric trifluoroacetate at elevated temperatures. Similar syntheses of bispentachlorophenylmercury from mercuric difluoroacetate and fluoroacetate have also been carried out. From merouration of pentaohlorobenzene with mercuric trifluoroaoetate and difluoroacetate under milder conditions, pentachlorophenylmercuric trifluoroacetate and difluoroacetate have been obtained. The former undergoes thermal decomposition into bispenta chlorophenylmercury and mercuric trifluoroacetate.

FREE RADICALS BY MASS SPECTROMETRY: XXXII. THERMAL DECOMPOSITION OF CYCLOPENTYL RADICALS

1965 ◽  
Vol 43 (3) ◽  
pp. 565-569 ◽  
Author(s):  
T. F. Palmer ◽  
F. P. Lossing
Keyword(s):  
Mass Spectrometry ◽  
Thermal Decomposition ◽  
Free Radicals ◽  
Elevated Temperatures ◽  
Bond Rupture ◽  
Low Pressures

At low pressures and elevated temperatures cyclopentyl radicals are found to dissociate mainly by two modes of reaction: about 34% by loss of H atom to form cyclopentene, and about 66% by a C—C bond rupture to form ethylene and allyl radicals. Under the conditions employed no evidence for a third possible mode, the loss of H2 to form cyclopentenyl radical, could be found. It is estimated that an incidence of 2% of the latter could have been detected.

Crystal Structure Stabilization of Gadolinium Aluminum Garnet (Gd3Al5O12) and Photoluminescence Properties

2013 ◽  
Vol 544 ◽  
pp. 245-251 ◽  
Author(s):  
Jin Kai Li ◽  
Ji Guang Li ◽  
Xiao Li Wu ◽  
Shao Hong Liu ◽  
Xiao Dong Li ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Solid Solutions ◽  
Elevated Temperatures ◽  
Particle Morphology ◽  
Mixed Solution ◽  
Photoluminescence Properties ◽  
Hydrogen Carbonate ◽  
Ammonium Hydrogen ◽  
Structure Stabilization

To suppress the thermal decomposition and to stabilize the crystal structure of Gd3Al5O12 (GdAG) garnet, doping GdAG with smaller Ln3+ (Ln=Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, respectively) to form (Gd,Ln)AG solid solutions was proposed in work. Carbonate precursors of (Gd,Ln)AG with an approximate composition of (NH4)x(Gd,Ln)3Al5(OH)y(CO3)z•nH2O were synthesized via coprecipitation from a mixed solution of ammonium aluminum sulfate and rare earth nitrate, using ammonium hydrogen carbonate as the precipitant. The precursors and the calcination derived oxides were characterized using FT-IR spectroscopy, DTA/TG, XRD, BET and FE-SEM. The results showed that smaller Ln3+ doping can indeed stabilize GdAG against its thermal decomposition to a mixture of GdAlO3 (GdAP) and Al2O3 phases at elevated temperatures and at the same time effectively lowers the temperature for garnet crystallization. The carbonate precursors are loosely agglomerated and the resultant (Gd,Ln)AG powders show good dispersion and a fairly uniform particle morphology. The (Gd,Ln)AG solid solutions exhibit decreasing lattice parameters along with decreasing radius of the dopant ions at the same dopant content of 50 at%. Photoluminescence properties of some of the garnet solid solutions are also studied. The materials developed herein may potentially be used for photoluminescent and scintillation applications.

scholarly journals Thermal stability of polyurethane coating prepared by using diphenylolpropane

2020 ◽  
Vol 62 (4) ◽  
pp. 81-87
Author(s):  
Indira N. Bakirova ◽  
Keyword(s):  
Thermal Stability ◽  
Thermal Decomposition ◽  
Weight Loss ◽  
Elevated Temperatures ◽  
Onset Temperature ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Polyurethane Coating ◽  
Urethane Group ◽  
Thermal Stability Of

Thermal stability of polyurethane varnish coating prepared by using diphenylolpropane, polyetherpolyol and polyisocyanate with an equimolar ratio of isocyanate and hydroxyl groups was assessed in the air. The polyurethane weight loss thermogram shows three temperature regions: I – (217-275)°С, II – (275-380)°С, and III – above 380°С. For interpreting thermogram of the polyurethane under study the model substances simulating the urethane groups of a polymer were synthesized. The substance containing the urethane group formed by phenolic hydroxyl of diphenylolpropane was shown to demonstrate relatively low thermal stability and gets broken down into isocyanate and bisphenol. Decomposition of the substance containing the urethane group formed by alcoholic hydroxyl occurs at the higher temperature. The data obtained allow interpreting the occurrence of thermal decomposition step I in TGA curve by structural changes in the blocks formed by diphenylolpropane and polyisocyanate being the least stable when exposed to elevated temperatures. The next step can be attributed to decomposition of more thermostable urethane groups formed by functional groups of oligooxypropylenetriol and polyisocyanate. Transition to the step III accompanied by severe sample weight loss due to decomposition of urethane groups is explained by thermal oxidation of oligoether units of polymer. Based on the data obtained the conclusion was made that the presence of urethane groups formed by phenolic hydroxyl of diphenylolpropane in polymer structure results in the decreased thermooxidative decomposition onset temperature of polymer. At the same time, a deceleration of thermooxidative processes due to the stabilizing effect of diphenylolpropane released at the beginning of thermal decomposition of polyurethane is observed in a high-temperature region. The proposed polyurethane coating is inferior to commercial counterparts in thermal decomposition onset temperature but superior to them in the temperature corresponding to a 50% polymer weight loss.

Laser-Processing for Patterned and Free-Standing Nitride Films

1997 ◽  
Vol 482 ◽  
Author(s):  
M. K. Kelly ◽  
O. Ambacher ◽  
R. Dimitrov ◽  
H. Angerer ◽  
R. Handschuh ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Laser Processing ◽  
Elevated Temperatures ◽  
Pulsed Laser ◽  
Nitride Semiconductors ◽  
Free Standing ◽  
Nitrogen Gas ◽  
Buried Interfaces ◽  
Growth Substrates

AbstractFilms of GaN and related materials can be processed by methods that invoke thermal decomposition, induced by intense illumination with a pulsed laser. At elevated temperatures, the nitride semiconductors undergo decomposition, with the effusion of nitrogen gas. We exploit this mechanism as an alternative to etching for the patterning of nitride films and for the opening of buried interfaces. Films of GaN have been etched to a depth of 1 μm in less than three seconds. This interface decomposition allows in particular the separation of nitride films from transparent growth substrates such as sapphire.

Synthesis and Thermal Characteristics of Complex Metal Hydride: NaAlH4

2003 ◽  
Vol 801 ◽  
Author(s):  
Bouziane Yebka ◽  
Gholam-Abbas Nazri
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Alkali Metals ◽  
Elevated Temperatures ◽  
Thermal Characteristics ◽  
Heating Rates ◽  
Complex Metal ◽  
Intermediate Phases ◽  
Initial Evolution ◽  
Decomposition Pathway

ABSTRACTComplex metal hydrides of general formula, ABH4 (A = alkali metals, B = third group elements such as B, Al, Ga) are potential candidates as hydrogen storage media for transportation. Thermal decomposition of complex hydrides generates hydrogen at elevated temperatures. The by -products of the dehydrogenation process can be regenerated using gaseous hydrogen at suitable temperature and pressure. The initial steps of thermal decomposition of NaAlH4 may be more complicated from the decomposition pathway reported in the literature. Close examination using thermal analysis by TGA, DSC and XRD measurements over the temperature range 30–500°C showed that the initial evolution of hydrogen occurred at a slow rate at ∼80°C, prior to fast decomposition at 190°C and at 260°C. Four regions of weight loss and five major endothermic peaks were measured during the thermal analysis. The effect of heating rate on the thermal analysis response showed that a high resolution of the thermal processes could be achieved at higher heating rates. Thermodynamic data was obtained for the various steps in the decomposition process including the formation of intermediate phases Na 3AlH6, and NaH. We also found that the decomposition of NaH is highly pressure dependent probably due to the high compressibility of the diffuse H− anion. The crystal-chemistry of NaAlH4 during decomposition has been established using X-ray diffraction analysis.

Organomercury compounds. XXII. Syntheses of polybromophenylmercurials by decarboxylation reactions

1977 ◽  
Vol 30 (5) ◽  
pp. 1013 ◽  
Author(s):  
GB Deacon ◽  
GJ Farquharson ◽  
JM Miller
Keyword(s):  
Thermal Decomposition ◽  
Sodium Chloride ◽  
Mass Spectra ◽  
Mercuric Acetate ◽  
Similar Treatment ◽  
Phenylmercuric Acetate ◽  
Pyridine Complexes ◽  
Organomercury Compounds ◽  
Mercuric Halides

The mercuric polybromobenzoates, (C6Br2CO2)2Hg, (XC6Br4CO2)2Hg (X = p-F, p-Cl, p-Me, o-Me, p-MeO or m-MeO) and (2,6-Me2C6Br3CO2)2Hg, and phenylmercuric pentabromobenzoate have been prepared by reaction of mercuric acetate or phenylmercuric acetate with the appropriate polybromobenzoic acids. Thermal decomposition of (C6Br5CO2)2Hg, (XC6Br4CO2)2Hg, (X = p-F, p-Cl or p-MeO) and C6Br5C02HgPh in boiling pyridine gave the new polybromophenylmercurials (C6Br&Hg, (XC6Br4)2Hg and C6Br5HgPh respectively, but similar treatment of (XC6Br4C02)2Hg (X = p-Me, o-Me or m-MeO) and (2,6-Me2C6Br3C02)2Hg yielded pyridine complexes of the mercuric carboxylates. Mercuric p-methyltetrabromobenzoate underwent decarboxylation in boiling nitrobenzenelpyridine giving (p-MeC6Br4),Hg, but the method could not be extended to (0-Mec~Br~C0~)o~r H(2g,6 -Me2C6Br,C02)2Hg. Decarboxylation of XC6Br4C02H (X = o-Me or m-MeO) was effected in molten mercuric trifluoroacetate giving, after treatment of the products with sodium chloride, the corresponding tetrabromophenylmercuric chlorides. All mercurials underwent cleavage with iodine or triiodide ions in hot dimethylformamide to give the corresponding iodopolybromobenzenes, and (C6Br5)2Hg was converted into C6Br5HgX (X = C1 or Br) by the corresponding mercuric halides in hot xylene/nitrobenzene. Thermal symmetrization of C6Br5HgX (X = C1, Br, or Ph) is detectable prior to melting, but (C6Br5),Hg is stable to at least 400'. The mass spectra of the polybromophenylmercurials are discussed.

THE REACTION OF CYCLOPENTANE VAPOR WITH Hg 6(3P1) ATOMS AT ELEVATED TEMPERATURES: THE RECOMBINATION, DISPROPORTIONATION, AND DECOMPOSITION OF CYCLOPENTYL RADICALS

1964 ◽  
Vol 42 (2) ◽  
pp. 357-370 ◽  
Author(s):  
Harry E. Gunning ◽  
Richard L. Stock
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Elevated Temperatures ◽  
Arrhenius Plot ◽  
New Products ◽  
Reaction Vessel ◽  
Rate Data ◽  
Kcal Mole ◽  
Low Light ◽  
Ethylene Propylene

The static reaction of Hg 6(3P1) atoms with cyclopentane vapor (c-C5H10) has been studied with temperatures from 26 to 376°, at constant c-C5H10 concentration and at low light intensities.From 26 to 250°, the only important products are hydrogen, cyclopentene, and bicyclopentyl. Above 250° new products appearing are ethylene, biallyl, and allyl cyclopentane, together with smaller yields of propylene, ethane, propane, and methane. To 250°, the reaction can be explained in terms of a 5-step paraffinic sequence, involving initial C—H scission to form H atoms and cyclopentyl (c-C5H9) radicals. The Arrhenius plot of a function equal to kdisp/kcomb for c-C5H9 radicals showed that Edisp−Ecomb = 0. Above 250° c-C5H9 radicals decompose into C2H4 and C3H5 radicals. The activation energy for this process was determined from a number of product functions to be 36.9 ± 1.2 kcal/mole. Evidence was also found for scission of c-C5H9 into cyclopentene and H atoms, above ca. 300°.A brief examination was also made of the thermal decomposition of c-C5H10 up to 457° in a quartz reaction vessel. The substrate is unstable above 350° forming ethylene, propylene, cyclopentene, cyclopentadiene, and hydrogen. The rate data can be satisfactorily explained by two intramolecular decompositions of the substrate into (a) ethylene and propylene and (b) cyclopentene and hydrogen with the cyclopentene further dehydrogenating to cyclopentadiene. From the data Ea = 49.6 ± 2.0 kcal/mole and Eb = 44.0 ± 2.0 kcal/mole.

Effects of CO2 on Carbon Nanotube Formation from Thermal Decomposition of Ethylene

2015 ◽  
Vol 1747 ◽  
Author(s):  
Chuanwei Zhuo ◽  
Fariba Khanshan ◽  
Richard West ◽  
Henning Richter ◽  
Yiannis A. Levendis
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Vapor Deposition ◽  
Elevated Temperatures ◽  
Chemical Vapor ◽  
Tubular Structures ◽  
Ethylene Decomposition ◽  
Model Predictions ◽  
Simulation Results

AbstractCatalytic chemical vapor deposition (CVD) is a popular method to synthesize carbon nanotubes (CNTs). At the presence of catalysts (usually trasition metals), the hydrocarbon feedstock decomposes controllably at elevated temperatures and can form tubular structures. It has been suggested that trace amounts of weak gas-phase oxidants, such as CO2, can enhance the CNT synthesis by extending the catatlyst life. It is not clear, however, how such additives affect the CVD reaction environment. In this study, ethylene gas was introduced to a preheated furnace/CVD reactor where meshes of stainless steel were placed. Therein ethylene was thermally decomposed in nitrogen mixed with different amounts of carbon dioxide. The meshes served as catalytic substrates for the CNT growth. The compositions of the ethylene pyrolyzates were analysed both with and without the presence of catalysts, to explore the possible contributions of CO2 addition to the CNT formation. The latter compositions were compared with kinetic model predictions of the thermal decomposition of ethylene. Both experimental and simulation results indicated that 1,3-butadiene (C4H6) was the most abundant hydrocarbon species of ethylene decomposition (at 800 °C) and that decomposition was inhibitted at the presence of CO2. A commesurate effect on CNT formation was observed experimentally, whereas the quality of CNTs got improved.

Reactivity of Isoprenic and Analogous Hydrocarbons towards Thiocyanic Acid and Dithiocyanogen

1946 ◽  
Vol 19 (1) ◽  
pp. 34-35
Author(s):  
Ralph F. Naylor
Keyword(s):  
Thermal Decomposition ◽  
Hydrogen Sulfide ◽  
Hydrogen Cyanide ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Amorphous Powder ◽  
Hydrogen Halides ◽  
Potential Source ◽  
Thiocyanic Acid ◽  
Methyl Thiocyanate

Abstract By analogy with hydrogen halides and hydrogen sulfide it is reasonable to expect thiocyanic acid to react with olefins, and it has been reported by Kharasch, May, and Mayo that it will add to isobutylene at room temperature to give a mixture of tert.-butyl thiocyanate and isothiocyanate. Under similar conditions in the present work, the only product that was obtained from cyclohexene and thiocyanic acid was a small quantity of an amorphous powder, probably mainly a perthiocyanic acid, formed by elimination of hydrogen cyanide from three molecules of thiocyanic acid. This tendency towards decomposition of the reagent prevented the use of elevated temperatures, and when methyl thiocyanate (a potential source of SCN and Me radicals by thermal decomposition) was heated at 170° with 1-methylcyclohexene and a little benzoyl peroxide (as catalyst), it underwent but slight reaction, the drop or two of product giving analytical values which suggested that it might be an impure adduct. Attempts to catalyze the addition of thiocyanic acid to, rubber included the use of ultraviolet irradiation, and of aluminum chloride or ferric chloride as catalyst. The most successful of these attempts was with ultraviolet light, but even then the product contained only 1.95% of sulfur, which represented 6% addition to the double bonds of rubber.

Organomercury compounds. XVIII. Thermal decomposition reactions of mercuric arenesulphonate pyridinates

1973 ◽  
Vol 26 (9) ◽  
pp. 1893 ◽  
Author(s):  
PG Cookson ◽  
GB Deacon
Keyword(s):  
Thermal Decomposition ◽  
Decomposition Reactions ◽  
Organomercury Compounds

The mercuric arenesulphonate pyridinates, Hg(O3SR)2,(py)2 (R = C6X5, p- HC6X4, o-HC6X4, or m-HC6Cl4; X = Cl or F) and Hg(O3S-m-HC6F4)2,(py)3, have been prepared by treatment of the appropriate mercuric arenesulphonate dihydrates with pyridine. Thermal decomposition of the compounds Hg(O3SR)2,(py)2 (R = C6X5, p-HC6X4, or m-HC6Cl4) and Hg(O3S-m-HC6F4)2,(py)3 at c. 120-240� under vacuum gave the corresponding diarylmercurials (yields: 45-90%) and the complex (py),SO3 in all cases, together with (- m-HgC6F4SO3-)n, and low yields of polyfluorobenzenes and/or polyfluorobenzenesulphonic acids. Similar decomposition of the compounds Hg(O3S-o-HC6X4)2,(py)2 gave (-o-HgC6X4SO3-)n, (py),SO3, o- HC6X4SO3H, and o-H2C6X4, and there was some evidence for formation of a trace of o-(o-HC6Cl4- SO3Hg)C6Cl4SO3HgO3S-o-HC6Cl4. The derivatives (- HgC6X4SO3-)n, were identified by established degradation procedures.

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