Thermolysis ammonium

The hydroxyl derivative of X-CN is cyanic acid HO-CN it cannot be prepared pure due to rapid decomposition but it is probably present to the extent of about 3% when its tautomer, isocyanic acid (HNCO) is prepared from sodium cyanate and HCI. HNCO rapidly trimerizes to cyanuric acid (Fig. 8.25) from which it can be regenerated by pyrolysis. It is a fairly strong acid (Ka 1.2 x 10 at 0°) freezing at —86.8° and boiling at 23.5°C. Thermolysis of urea is an alternative route to HNCO and (HNCO)3 the reverse reaction, involving the isomerization of ammonium cyanate, is the clas.sic synthesis of urea by F. Wohler (1828) ... 

Uncatalyzed amidations of acids have been realized under solvent-free conditions and with a very important microwave effect [67 a]. The best results were obtained by use of a slight excess of either amine or acid (1.5 equiv.). The reaction involves thermolysis of the previously formed ammonium salt (acid-base equilibrium) and is promoted by nucleophilic attack of the amine on the carbonyl moiety of the acid and removal of water at high temperature. The large difference in yields (MW > A) might be a consequence of interaction of the polar TS with the electric field (Eq. (15 a) and Tab. 3.6). 

Photolysis or thermolysis of heteroatom-substituted chromium carbene complexes can lead to the formation of ketene-like intermediates (cf. Sections 2.2.3 and 2.2.5). The reaction of these intermediates with tertiary amines can yield ammonium ylides, which can undergo Stevens rearrangement [294,365,366] (see also Entry 6, Table 2.14 and Experimental Procedure 2.2.1). This reaction sequence has been used to prepare pyrrolidones and other nitrogen-containing heterocycles. Examples of such reactions are given in Figure 2.31 and Table 2.21. 

Many different types of 1,3-dipoles have been described [Ij however, those most commonly formed using transition metal catalysis are the carbonyl ylides and associated mesoionic species such as isomiinchnones. Additional examples include the thiocar-bonyl, azomethine, oxonium, ammonium, and nitrile ylides, which have also been generated using rhodium(II) catalysis [8]. The mechanism of dipole formation most often involves the interaction of an electrophilic metal carbenoid with a heteroatom lone pair. In some cases, however, dipoles can be generated via the rearrangement of a reactive species, such as another dipole [40], or the thermolysis of a three-membered het-erocycHc ring [41]. 

In acid catalysis (HCl), the variation in pH of the medium affects the yield of oligoorganylsilsesquioxanes to a lesser extent than in the case of alkaline catalysis. Base catalysts are used in the synthesis of oligosilsesquioxanes mainly in the thermolysis of the primary products of XSiYj hydrolysis (Table 1). The most efficient catalysts, in this case, are those which are readily decomposed upon heating to give inactive products For example, the use of tetraethylammonium 32,45) trimethyl-benzyl ammonium 23.37,41) triethylamine hydroxides has proved successful. 

Borazine, B3N3H6, was first prepared by thermolysis of the diborane ammonia adduct [(BH2)(NH3)2] [BH4] . More convenient procedures for the laboratory preparation of this important ring system in multigram quantities involve either (a) the decomposition of ammonia- borane [eqn (9.1)] or (b) the reaction between ammonium sulfate and sodium borohydride [eqn (9.2)]. The latter method provides a convenient and economical synthesis of borazine. 

The obtention of nitrides by thermal decomposition of the azides was only successful for the synthesis of [MNBr4]2- from [MN3Br5] . Thermolysis of MX5 with ammonium salts afforded a more general access to nitride halides in oxidation state V, or IV if higher temperatures were used.316,317 Oxo nitrides were obtained if moisture was admitted during the process.318... 

Diamagnetic polymeric nitrides, [TaNBr] 324 and [NbNI] ,325 have been obtained by high temperature thermolysis of MXS with ammonium salts. 

The increase in the rate of decomposition under the influence of added Cr203 and K2Cr207 is shown on Figs. 171 and 172 respectively.lt has been found that an increase of the rate occurred only at temperatures near to the melting point of the samples. Guiochon [17] also found that cobalt salts increase the rate of thermolysis of ammonium nitrate. Other mineral salts (of manganese, nickel and copper) have a similar but much weaker action. A large number of salts of other metals are without any noticeable action. 

Presumably, the Si—H bond in the cationic species points toward one of the ammonium protons, thus favoring an easy hydrogen elimination by their thermolysis (equation 187)413. 

One of the earliest preparations of the 1,2,4-dithiazole (30) was by acid treatment of a concentrated aqueous solution of 2-thioxo-l,3-thiazolidin-4-one ( rhodanic acid ) (1842LA(43)76) or of one of its salts Ac20 with the> ammonium salt gave the /V-acetyl derivative (1873CB902). Thermolysis of 2-phenyl-l,3-tbiazoline-4,5-dio ne leads via loss of CO to thiobenzoylisocyanate, which with sulfur or P4S10 yields a dithiazolinethione (Scheme 4D. 

Kirilenko et al. (2005) XAS, TGA wo3 Phase transformation, redox behavior + + n.a. Thermolysis of ammonium para tungstate... 

Oxidation of these complexes releases the apical carbon atom and its substituent in the form of an organic derivative.2 Thus ceric ammonium nitrate oxidation of an RCCo3(CO)9 complex produces the carboxylic acid, RC02H, when the reaction is carried out in aqueous acetone. Thermolysis of RCCo3(CO)9 produces acetylenes or acetylene hexacarbonyl dicobalt complexes, depending on the reaction conditions. Useful applications of these cluster complexes in organic synthesis remain to be developed. 

Chromium can exist in several oxidation states and early EPR studies suggested that the catalytic activity of chromia is related strongly to the presence of different oxidation states on the surface [46]. Small amounts of Cr>3+ in chromia can be attributed to high temperature synthesis procedures (e.g. incomplete thermolysis of ammonium dichromate), however, oxidized Cr-sites can also be formed in contact... 

Nitrides can be obtained by decomposition of the azides, but thermolysis of the pentahalides with ammonium salts appears more general. Recent synthetic pathways involve the cleavage of N2 or decarboxylation of a Nb isocyanate." The solid-state characterization of the [M2NXio] anions shows a linear symmetrical M=N=M bridge. Neutral halide nitrides are polymeric. Heterometallic nitrides based on a comer-shared double cube NbTieNg core (27) have been described (equation 14). ... 

Pure tetrazene 52 is substantially more thermostable than pure tetrazene 51 (Table III). Also, the decomposition of 52 occurs according to Thermolysis Pathway IV to give hydrazoic acid and bis(trimethysilyl)amine, which in turn react further with each other to form trimethylsilylamine and ammonium azide (42), as shown in Eq. (60). 

Monosubstituted tetrazene (Mc3Si)HN— N=N— NH2 is very thermo-labile (41, 42). In methylene chloride it decomposes above ca. -40 C with the formation of trimethylsilyl azide and bis(trimethylsilyl)amine, as well as ammonium azide. Thus, the (catalyzed ) decomposition of the compound follows Thermolysis Pathway IV. 

Hoffmann degradation is a classic way to transform aporphines into phe-nanthrene alkaloids. This transformation involves the thermolysis of the quaternary ammonium hydroxide formed by sequential treatment of an aporphine with an alkylating agent and silver oxide. This degradation was extensively used in initial degradative studies of the structure of aporphines. The alkylations are usually done with methyl iodide (20,30,45,60,85,86,88) or dimethyl sulfate... 

The only direct study of the chemical reactivity of the thiaziridine system was conducted on the thiaziridine 1,1-dioxide system 19, the only thus far isolable compounds of the thiaziridine series. As could be predicted and in line with theoretical considerations, thermolysis of alkyl-substituted thiaziridine 1,1-dioxides 19a,d,e afforded aldimines 60a,d,e as a result of the cheletropic extrusion of the sulfur dioxide moiety (Scheme 9) <1981CB774>. Treatment of these thiaziridine 1,1-dioxides with perchloric acid has also resulted in the loss of sulfur dioxide with the concomitant formation of the corresponding ammonium perchlorate salts 61 <1981CB774>. 

Calcium oxalate normally is precipitated as the monohydrate from hot solution. The thermolysis curve shows several plateaus, corresponding to the monohydrate from room temperature to 100°C, anhydrous calcium oxalate from 226 to 398°C, calcium carbonate from 420 to 660°C, and calcium oxide above 840 to 850°C. Sandell and Kolthoff concluded that the monohydrate is not a reliable weighing form because of its tendency to retain excess moisture. Coprecipitated ammonium oxalate also remains undecomposed, so the results are usually 0.5 to 1.0% too high when the precipitate is dried at 105 to 110°C. Anhydrous calcium oxalate also is unsuitable as a weighing form because of its hygroscopicity. 

Heating of ammonium salt (562) generated intermediate 563, which could be trapped by methanol leading to substitution product 564 Thermolysis of 562 in the absence of... 

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