Compound thermal dissociation

Other, less common methods that have been used to generate sulphonamidyls include direct hydrogen atom abstraction from the parent sulphonamide using Pb(OAc)4 or t-BuO (equation 10)28-30, which has the advantage that it does not require an extra synthetic step to synthesize the AT-halo substituted compound, thermal dissociation of a l,2-bis(sulphonyl)hydrazine (equation 11)31 and, for one solid state study, y-irradiation of the sulphonamide (equation 12)32. 

In flame spectroscopy, a solution is aspirated into a flame and the inorganic compounds thermally dissociated into atomic vapor. There are three types of flame spectroscopy atomic absorption, atomic emission, and atomic fluorescence. The first two techniques will be emphasized because commercial instruments are widely available for these, whereas atomic fluorescence is used more for specific applications and as a research tool. Many of the points made with respect to flame chemistry, interferences, and so forth apply also to atomic fluorescence. Various types of atomic fluorescence and the specific instrumentation required are considered at the end of the chapter. 

Tantalum. Numerous methods developed to extract tantalum metal from compounds included the reduction of the oxide with carbon or calcium the reduction of the pentachloride with magnesium, sodium, or hydrogen and the thermal dissociation of the pentachloride (30). The only processes that ever achieved commercial significance are the electrochemical reduction of tantalum pentoxide in molten K TaF /KF/KCl mixtures and the reduction of K TaF with sodium. 

New sources of RaSn- radicals that have been developed include the reversible thermal dissociation of bis(trialkylstannyl)pinacols (290-292), the )3-scission of /3-stannylalkyl radicals (293), and the photolysis of cyclopentadienyltin compounds (294). 

The reaction takes place probably by a kind of inverse Wittig reaction , corresponding to the thermal dissociation of an oxaphosphetene resulting from a [2+2] cycloaddition between the phosphine oxide and the activated acetylenic compounds (Scheme 2) [11,12]. 

Other probable cases of addition of CO to complete a molecule by thermal reactions are Mo(CO)6 (99), W(CO)6 61, 99) [CpFe(CO)2]2 (59), Fe(CO)5 in [CpFe(CO)2]2 (50), IMn(CO)5 48), and Ni(CO)4 (92). This last seems to show the importance of normal thermal dissociation, although radiolytic effects have not been ruled out. Most other ligands which have been studied have, on one compound or another, been found to be capable of thermal reaction—Ph in AsPhj, CO in several compounds, I and Br in XMn(CO)j, Cp in FeCp2, PhH in Cr(PhH)2. Many of these same ligands have also been found to react prethermally in other cases. 

Two U.S. patents issued to the Barium Steel Corporation in 1957 claim the formation of the heptacarbonyls M(CO)7 (M = Ti, Zr, Hf) as intermediates for the purification of these metals (9,10). In this described refining process, the finely divided metal is treated with CO at 300-400°C and 4-8 atm. The resulting liquid heptacarbonyl compound is then thermally dissociated to the pure metal and CO. The alleged existence of these binary carbonyls seems highly unlikely without supporting evidence. 

Alternatively, the compound may he prepared by thermal dissociation of diacetyltartaric anhydride. 

HCl also may be prepared by several other methods including thermal dissociation of aluminum chloride hexahydrate, AICI3 6H2O, and as a by-product of manufacturing many organic compounds. 

Elemental composition Mo 36.34%, C 27.30%, 0 36.36%. A benzene solution of the hexacarbonyl may be analyzed by GC/MS. Molybdenum metal digested in nitric acid solution may be analyzed by various instrumental techniques. Also, the compound may be thermally dissociated and the liberated CO may be identified by GC using a TCD or by GC/MS using an appropriate capillary column. 

The vapour pressure ratio of actinides to noble metals is also the basis of the actinide metal preparation by thermal dissociation of intermetallic compounds. Such intermetallic compounds of An and noble metals can be prepared by hydrogen reduction of a mixture of an An oxide and a finely divided noble metal (Pt, Ir.. in the absence of noble metals, hydrogen reduction of An oxides is impossible. Am and Cm metals have been obtained by thermal dissociation of their intermetallic compounds with Pt and Ir High purity Th and Pa, the least volatile actinide metals, can be prepared by thermal dissociation of their iodides, which form readily by reaction of iodine vapour with car-... 

Well defined oxide phases can be obtained by thermal dissociation of oxalates, by controlled oxidation of compounds or actinide saturated ion exchangers or by reduction of higher oxides with hydrogen. Thermal dissociation of compounds often results in oxides of low density high (almost theoretical) density oxides can be prepared in sol-gel processes. 

The compositions of the most numerous actinide compounds with elements of the group V of the periodic table (X = N, P, As, Sb, Bi) belong to the types AnX2, An3Xt, AnX. These pnictides can be synthesized in solid-gas-reactions with actinide hydride, or with metal powder obtained by thermal dissociation of hydrides. 

Protactinium dipnictides (X = As, Sb) have been synthesized by reaction of As or Sb vapour with metal hydride at 400-700 Pa3As4 was obtained by thermal dissociation of PaAs2 at 840 °C, Pa3Sb4 from the corresponding dipnictide at 1200 °C. Monopnictides of protactinium were not obtained by thermal dissociation of higher compounds. The diantimonides of the transuranium elements Np, Pu, Am dissociate between 700-800 °C into the monocompounds. Monopnictides of the higher transuranium elements have been obtained at the pg scale with and 0 by thermal dissociation. 

Powder Formation. Metallic powders can be formed by any number of techniques, including the reduction of corresponding oxides and salts, the thermal dissociation of metal compounds, electrolysis, atomization, gas-phase synthesis or decomposition, or mechanical attrition. The atomization method is the one most commonly used, because it can produce powders from alloys as well as from pure metals. In the atomization process, a molten metal is forced through an orifice and the stream is broken up with a jet of water or gas. The molten metal forms droplets to minimize the surface area, which solidify very rapidly. Currently, iron-nickel-molybdenum alloys, stainless steels, tool steels, nickel alloys, titanium alloys, and aluminum alloys, as well as many pure metals, are manufactured by atomization processes. 

A great many compounds exert a considerable vapor pressure because of thermal dissociation, with the production of one or more gaseous components. Such is the case with efflorescent hydrates. Other examples are the compounds (NH4)2S, WC16, PCU and many ammoniates, such as AgCl-3NH3. The extent of dissociation is... 

It seems that the cavities enclose a vapor of the solute because of the high vapor pressure of these compounds. The primary reaction pathway for these compounds appears to be the thermal dissociation in the cavities. The activation energy required to cleave the bond is provided by the high temperature and pressure in the cavitation bubbles. This leads to the generation of radicals such as hydroxyl radical, peroxide radical, and hydrogen radical. These radicals then diffuse to the bulk liquid phase, where they initiate secondary oxidation reactions. The solute molecule then breaks down as a result of free-radical attack. The oxidation of target molecules by free radicals in the bulk liquid phase under normal operating pressures and temperatures can be presented by a second-order rate equation ... 

Two general methods may be employed in the preparation of hydroxylamine involving either the thermal dissociation of certain hydroxylamine compounds or the interaction of hydroxylamine hydrochloride suspended in an alcohol with the corresponding sodium alcoholate. The first of these methods was used both by Crismer,1 who distilled zinc chloride dihydroxylamate under reduced pressure and by Uhlenhut,2 who decomposed tertiary hydroxylamine phosphate. These procedures are extremely wasteful, owing to the instability of hydroxylamine at the temperatures required to bring about dissociation. Any hydroxylamine that is not isolated is totally lost. 

Thermal stability. The degree to which a compound resists dissociation or other chemical alteration at elevated temperatures. Magnesium oxide is stable up to its melting point (2800° C.) and beyond, and hence is considered to have high thermal stability calcium bicarbonate decomposes at 100° to carbon dioxide, water, and calcium carbonate, and hence is thermally unstable. As used in the text, the term indicates chemical integrity up to a designated temperature. 

Okamoto et al. (1973,1973a, 1973b) measured photogeneration efficiencies of PVK. The results were explained by the field-assisted thermal dissociation of an exciplex formed between an excited carbazole group and an acceptor impurity. Okamoto et al. (1975) measured the efficiencies of /3-N-caibazolyl-ethyl vinyl ether, an oligomer of N-vinylcaibazole, and PVK. The efficiencies of the three compounds were comparable. The results were described by the dissociation of singlet excitons. 

At 200 C, neither COBr2 nor HCOBr is a stable compound. Propose a radical chain to account for the thermal bromination of CH2O to produce CO -f HBr with the initiation step being the thermal dissociation of Br2. Neglect wall reactions. Compute expressions for the stationary-state concentrations of all radical species and the rate e pression for —dCBT )/dt, Try to justify all steps included in the scheme. 

The overall activation energy is about 102.5 kJ mol 1 and is equal to half of that for the thermal dissociation of peroxide bonds. The alcohols, especially allylic compounds,... 

Thus, compound 23, with a i/(Sn-Sn) of 102 cm , appears to thermally dissociate beginning at 180°C, compound 24 at 100°C [i/(Sn-Sn) 92 cm ], and finally, compound 25, for which i lSn-Sn) cannot be measured, at only 20°C. Unfortunately, the structural parameters and the electronic spectra for compounds 2 25 have not yet been obtained, so a correlation between these parameters and their Sn-Sn bond lengths cannot be made. 

Quantitative data have been reported for the thermal dissociation of substituted tetrazanes (structurally related to hydrazo compounds) to hydrazyl free radicals, viz. 

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