Methylamine, decomposition

Operating in the oscillatory regime produced higher yields than did the steady state for the CO oxidation reaction over Pt (22) and Pd (23), and for the endothermic methylamine decomposition over Pt wires (24). In these cases comparison between oscillatory and steady states was possible because the unstable states coexisted with the respective stable states of the systems. 

One important oscillating system—namely, the methylamine decomposition on noble metal wires (24,143,227,228)—belongs to this class of ther-mokinetic blocking/reactivation models. This reaction is unique in several ways. It is the only endothermic oscillator (-1-150 kJ/mol), and it is the only unimolecular reaction that displays oscillations caused by sur ce effects. [The oscillating N2O decomposition, reported by Hugo (5) in 1968, does not oscillate because of the instability of the surface reaction, but rather due to the instability of a CSTR when certain heat and mass transfer conditions exist. Any reaction with similar rate and heat effects would oscillate under such circumstances.] This reaction is also the most vigorous oscillator yet observed and displays frequencies of up to 10 Hz and amplitudes approaching 500 K. Moreover, because the reaction oscillates at temperatures of around 1000 K, the oscillations can actually be observed visually as the metal catalyst heats and cools. 

Fig. 15. A comparison of experimental and simulated behavior for methylamine decomposition on Pt. (a) Temperature oscillations (b) predicted coverage oscillations of species a, CH3NH2, and b, a site blocker (c) simulated bifurcation diagram of temperature vs. current (d) experimental bifurcation diagram of temperature vs. current. (From Ref. 24.)...

In a more recent example, a shock-tube experiment was used to study the themial decomposition of methylamine between 1500 K and 2000 K [61, 62] ... 

Migration to the developing electron sextet at nitrogen is not restricted to hydrogen. In (79) there is methyl migration with formation of methylamine and acetone in the acid-catalyzed decomposition of (80), phenyl migration leads to aniline and acetaldehyde. 

The decomposition of a number of perchlorates containing substituted ammonium groups (various methylamines, guanadine etc.) [935—939] resemble the mechanism proposed for AP decomposition in that proton transfer is identified as the initial step. 

C. Miscellaneous.—Treatment of the phosphonium bromide (114) with one equivalent of butyl-lithium gave triphenylphosphine and benzylidene-methylamine via a Hofmann-like decomposition, whereas reaction with two equivalents of butyl-lithium resulted in the production of butyltriphenyl-phosphonium bromide. ... 

Additional Comments Regarding the Ruthenium Carbonyl-Tri-methylamine WGSR System. A potential mechanistic pathway for a WGSR system involves the production of formate, followed by its catalytic decomposition ... 

Soil. Soil metabolites include formaldehyde, hydrogen sulfide, methylamine, and methyl(methylaminomethyl)dithiocarbamic acid (Hartley and Kidd, 1987), the latter decomposing to methyl isothiocyanate (Ashton and Monaco, 1991 Hartley and Kidd, 1987 Cremlyn, 1991). The rate of decomposition is dependent upon the soil type, temperature, and humidity (Cremlyn, 1991). 

Chemical/Physical. Hydrolyzes in acidic solutions forming carbon disulfide, methylamine, and formaldehyde (Hartley and Kidd, 1987 Humburg et al, 1989). These compounds are probably formed following the decomposition of dazomet with alcohol and water (Windholz et al., 1983). Emits nitrogen and sulfur oxides when heated to decomposition (Sax and Lewis, 1987). 

Methylamine nitrate is a stable compound. Marked thermal decomposition starts at 195°C, and on raising the temperature to 235°C, oxides of nitrogen are developed. A sample of the substance thrown into a test-tube heated to 375-390°C explodes in 7 sec. 

The decomposition of (65) in an inert medium produces mainly nitrogen and a white solid residue, the composition of which has not been determined (76MI11502). Small quantities of methylamine, formaldehyde and other gaseous products have been identified among the decomposition products. It is used extensively in rubber goods, but its use in plastics has been limited by the high exotherm of decomposition and by the unpleasant odor of the residue. 

Methylamine. —The electric spark, when passed through methylamine vapor by Hofmann and Buff,5 gave primarily hydrogen and methylamine hydrocyanide further action brought about complete decomposition, tarry substances being deposited. 

Although the hydrogenation of hydrogen cyanide to methylamine was achieved as early as 1863 (Debus, 1), the history of modern catalytic hydrogenation began in 1897 with the discovery by Paul Sabatier and R. Senderens of the vapor phase hydrogenation of unsaturated compounds over a nickel catalyst (Sabatier and Senderens, 2). Sabatier has said that his interest in the action of nickel was provoked by the newly discovered Mond process for the purification of nickel by the formation and decomposition of nickel carbonyl. The capacity of nickel... 

The pure solvent has been found to decompose slightly - probably to an equilibrium mixture containing small quantities of methylamine and N,N-diacetylmethyl-amine17. This decomposition is accelerated by contact with a metal surface17. The formation of such decomposition products might be the primary cause of the problems involved in some of the purification procedures7. Decomposition apparently occurs slowly even in solid NMA. 

This compound, DTIC, 237, has been prepared240 on micro-scale in 67% yield starting with 5-180 //mol of di[14C]methylamine of high specific activity and with an excess of the diazo precursor (equation 99) employing a vacuum technique. The 14C-labelled DTIC has been used to investigate the decomposition mechanism and the biochemical fate of 237, which possesses an anti-tumor activity241. 

The compound is sensitive to solvolysis and thermally unstable. (NH)2Se is formed by decomposition above -40 °C. Using methylamine or ethylenediamine instead of ammonia, seleninyl ethylenediamide, (CH2NH)2SeO, can be obtained by an analogous reaction. By the reaction of seleninyl bis(dimethylamide) with seleninyl chloride, a dimethylamide of chloroselenic(IV) acid results (equation 56). 

Methylating agents can be generated by chemical ni-trosation of endogenous metabolites. For example, methylamine produced by the decomposition of organic matter can condense with carbamyl phosphate, a precursor of pyrimidines, to form methylurea, which in turn can be nitrosated to yield methylnitrosourea (MNU). Such nitrosation reactions can be catalyzed by bacterial enzymes (35). 

The second of these proceeds by a peroxy radical mechanism involving internal hydrogen abstraction followed by decomposition analogous to that suggested above. The radical produced in this process is CH3NH which in turn yields methylamine. 

An early study of the pyrolysis of methylamine reported the decomposition to follow a homogeneous first order path (500-670° C), viz. 

Methylamino. It has been suggested (5) that the initial step in the thermal decomposition of methylamine is... 

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