Ether thermal decomposition

Handling, Storage, and Precautions use in a fume hood best results are obtained with high-purity copper (I) salts, dry, O2-free solvents, and alkyllithium solutions free of contaminating alkoxides or hydroxides n-BuLi is pyrophoric, and due care must be exercised in its handling the reagent has greater stability in THF than in ether thermal decomposition is minimal at or below —25 °C but is substantial at 0 °C. ... 

Beryllium Hydride. BeryUium hydride [13597-97-2] is an amorphous, colorless, highly toxic polymeric soHd (H = 18.3%) that is stable to water but hydroly2ed by acid (8). It is insoluble in organic solvents but reacts with tertiary amines at 160°C to form stable adducts, eg, (R3N-BeH2 )2 (9). It is prepared by continuous thermal decomposition of a di-/-butylberylhum-ethyl ether complex in a boiling hydrocarbon (10). 

PTMEG is a polymeric ether susceptible to both thermal and oxidative degradation. It usually contains 300—1000 ppm of an antioxidant such as 2,6-di-/ f2 -butyl-4-hydroxytoluene (BHT) to prevent oxidation under normal storage and handling conditions. Thermal decomposition in an inert atmosphere starts at 210—220°C (410—430°E) with the formation of highly flammable THE. In the presence of acidic impurities, the decomposition temperature can be significantly reduced contact with acids should therefore be avoided, and storage temperatures have to be controlled to prevent decomposition to THF (261). 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

Thermal decomposition of LiR eliminates a /6-hydrogen atom to give an olefin and LiH, a process of industrial importance for long-chain terminal alkenes. Alkenes can also be produced by treatment of ethers, the organometallic reacting here as a very strong base (proton acceptor) ... 

Reaction of the glycol, 70, affords an oxazolidinone rather than the expected carbamate (71) on fusion with urea. It has been postulated that the urea is in fact the first product formed. This compound then undergoes 0 to N migration with loss of carbon dioxide reaction of the amino alcohol with the isocyanic acid known to result from thermal decomposition of urea affords the observed product, mephenoxolone (74) this compound shows activity quite similar to that of the carbamate. An analogous reaction on the glyceryl ether, 75, affords metaxa-lone (76). 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

Alcohol sulfates decompose at high temperature. At 100°C they lose any associated water and at 150°C thermal decomposition begins. The organic part of the molecule is completely decomposed at 285 °C. Main decomposition substances of sodium lauryl sulfate are dilauryl ether and sodium pyrosulfate [64]. 

We have studied the thermal decomposition of diaryl ether in detail, since the cleavage of ether linkage must be one of the most responsible reactions for coal liquefaction among the various types of decomposition reaction and we found that the C-0 bond of polynucleus aromatic ethers is cleaved considerably at coal liquefaction temperature. 

The apparent activation energy for the thermal decomposition of phenyl benzyl ether was calculated to be 50 kcal/mole, since the first order rate constants were 1.39x10 at 320°C, 5.19xl0"4 at 340°C and 9.52x10" S at 350°C, respectively. 

The Thermal Decomposition of Aromatic Ethers. According to the results of Table I, the bond scission of oxygen containing polynucleus aromatic structure of coal at liquefaction temperature of 450°C seems to occur mainly at methylene or ether structures. Therefore, it will be very important to study the... 

Thermal decomposition of seven diaryl ethers at various reaction conditions and the composition of reaction products are shown in Table II. 

TABLE II THERMAL DECOMPOSITION OF DIARYL ETHERS IN TETRALIN... 

The thermal decomposition of dibenzyl was not affected by the addition of phenol or p-cresol. In contrast, the decomposition of 2,2 -dinaphthyl ether increases remarkably in the presence of phenolic compounds as shown in Table III, and the effect seems to increase with increasing the electron donating property of substituent on the benzene nucleus. 

TABLE III EFFECT OF PHENOLS ON THE THERMAL DECOMPOSITION OF 2,2 -DINAPHTHYL ETHER AT 450°C FOR 60 MIN (2,2 -Dinaphthyl ether 11 mmole, Tetralin 225 mmole, Additive 150 mmole)... 

Accelerating Effect due to Phenols on the Rupture of Ether Linkages. Phenols are weak acids and polar solvent, and so often observed to enhance the thermal decomposition of covalent bond, but we could not observe any accelerating effect due to phenol on the decomposition of dibenzyl. 

TABLE V EFFECT OF COAL ASH ON THE THERMAL DECOMPOSITION OF DIARYL ETHERS (Ethers 4 mmole, Tetralin 40 mmole)... 

The thermal decomposition of />-nitrotriphenylmethyl hydroperoxide in benzene gives -nitrophenol 32%, phenol 9%, >-nitro-triphenylcarbinol 23%, -nitrobenzophenone 14%, and no benzo-phenone the decomposition in ether plus sulfuric acid gives -nitro-benzophenone 94% and phenol 81%.817 The latter reaction is very probably ... 

Suppose the mechanism for the thermal decomposition of dimethyl ether to methane and formaldehyde... 

Neomycin is insufficiently volatile for direct mass spectrometric analysis. To overcome this problem Inouye- - prepared the volatile N-salicylidene Schiff s base, the M.S. of which, however, did not exhibit a peak for the molecular ion. To observe the molecular ion it was necessary to use the o-trimethylsilyl ether of the N-salicylidene Schiff s base. The spectrum of N-salicylidene neomycin was found to be dependant on the ion-chamber temperature indicating that thermal decomposition plays a significant part in the fragmentation process. 

Thermal decomposition of diethyl ether is postulated by Hinshelwood (Kinetics of Chemical Change, 1941) to proceed by the chain mechanism. 

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). 

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). 

Classical organic chemistry provides a wide variety of potential analytes for electron ionization, the only limitation being that the analyte should be accessible to evaporation or sublimation without significant thermal decomposition. These requirements are usually met by saturated and unsaturated aliphatic and aromatic hydrocarbons and their derivatives such as halides, ethers, acids, esters, amines, amides etc. Heterocycles generally yield useful El spectra, and flavones, steroids, terpenes and comparable compounds can successfully be analyzed by El, too. Therefore, El represents the standard method for such kind of samples. 

The mechanism of pyrolysis reactions of biomass was extensively discussed in an earlier study (Demirbas, 2000). Water is formed by dehydration. In the pyrolysis reactions, methanol arises from the breakdown of methyl esters and/or ethers from decomposition of pectin-like plant materials. Methanol also arises from methoxyl groups of uronic acid (Demirbas and Giillii, 1998). Acetic acid is formed in the thermal decomposition of all three main components of wood. When the yield of acetic... 

---