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Very low‐pressure pyrolysis. VII. The decomposition of methylhydrazine, 1,1‐dimethylhydrazine, 1,2‐dimethylhydrazine, and tetramethylhydrazine. Concerted deamination and dehydrogenation of methylhydrazine
Author(s) -
Golden D. M.,
Solly R. K.,
Gac N. A.,
Benson S. W.
Publication year - 1972
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550040407
Subject(s) - chemistry , methylhydrazine , reaction rate constant , bond cleavage , homolysis , dimethylhydrazine , standard enthalpy of formation , computational chemistry , decomposition , thermal decomposition , photochemistry , radical , medicinal chemistry , organic chemistry , kinetics , medicine , physics , colorectal cancer , quantum mechanics , cancer , catalysis , phenylhydrazine
The rate constants ( k uni ) for the first‐order disappearance of the title molecules have been determined under VLPP conditions. The k uni are not the rate constants of ultimate interest since they reflect the fact that energy transfer competes with the chemical decomposition. Use of the Rice‐Ramsperger‐Kassel‐(Marcus) [RRK(M)] theory allows the determination of the high‐pressure rate constants ( k α ), if the mode of decomposition is known. The heats of formation of the radicals NH 2 , CH 3 NH, and (CH 3 ) 2 N are known. These values should be usable for prediction of the activation energy for NN bond homolysis in the hydrazines. Measured rate constants for UDMH and TMH bear this out, but the rate constant for MMH does not. This and other evidence lead to the conclusion that MMH decomposes via molecular concerted elimination of NH 3 and H 2 not and by NN bond scission. The following values are preferred from this work (θ = 2.303 RT in kcal/mole). Mode of decomposition is N—N bond scission unless noted otherwise in parenthesis:\documentclass{article}\pagestyle{empty}\begin{document}$$\begin{array}{ll} \underline{{{{\rm Molecule}}}}& \underline{{{{\rm log }k_\infty /\sec ^{ - 1} (298^\circ {\rm K})}}}\\ {{{{\rm MMH}}}}&{{{13.2{\rm - }54/\theta (- {\rm NH}_{\rm 3});}}}\\ {} & {13.5{\rm - }57/\theta (- {\rm H}_{\rm 2})} \\ {{\rm UDMH}} & {17.0{\rm - }63/\theta } \\ {{\rm SDMH}} & {{\rm 13}{\rm .5 - 57/}\theta {\rm (} - {\rm H}_{\rm 2} {\rm)}} \\ {{\rm TMH}} & {{\rm 17}{\rm .4 - 54/}\theta } \\\end{array}$$\end{document} .