- Lewis Acid Activation and Catalysis of Dialkylaminyl Radical Reactions
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Lewis acid activation and catalysis of dialkylaminyl radical reactions is demonstrated both qualitatively and quantitatively. Cyclization of the N-butyl-4-pentenaminyl radical (1) in the presence of a wide range of Lewis acids was shown to be efficient with good to excellent yields of cyclic products obtained in reactions conducted even at -78°C. Rate constants for fragmentation of the N-ethyl-2,2-diphenylethylaminyl radical (6), 6-exo cyclization of the N-methyl-6,6-diphenyl-5-hexenaminyl radical (7), and 5-exo cyclization of the N-methyl-5,5-diphenyl-4-pentenaminyl radical (8) in the presence of the Lewis acids LiBF4, MgBr2, and BF3 were measured by laser flash photolysis (LFP) methods. The LFP studies demonstrated saturation kinetic behavior with respect to the Lewis acids. Equilibrium binding constants for the Lewis acids with the dialkylaminyl radicals and rate constants for reactions of the Lewis acid complexed dialkylaminyl radicals were obtained from nonlinear regression analysis of the observed rate constants.
- Ha, Chau,Musa, Osama M.,Martinez, Felix N.,Newcomb, Martin
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p. 2704 - 2710
(2007/10/03)
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- Gas Phase Thermolysis of Allyl Cyanomethyl Amine, Diallyl Cyanomethyl Amine, Diethyl Cyanomethyl Amine, and Diethyl Propargyl Amine
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The title amines were pyrolyzed in a stirred-flow reactor at 380 - 510 deg C, pressures of 8 - 15 torr and residence times of 0.3 - 2.4 s, using toluene as carrier gas.The substrates with an allyl group yielded propene and iminonitriles as reaction products.HCN is formed by decomposition of the iminonitriles.The first-order rate coefficients for propene formation fit the Arrhenius equations.Allyl cyanomethyl amine: k(s-1) = 1013.29 +/- 0.35exp(-189 +/- 5 kJ/mol RT) Diallyl cyanomethyl amine: k(s-1) = 1013.00 +/- 0.20exp(-183 +/- 3 kJ/mol RT) Diethyl cyanomethyl amine gave a 20:1 gas mixture of ethylene and ethane, plus HCN.The liquid product fraction contained mainly N-ethyl methanaldimine.The first-order rate coefficients for ethylene formation followed the Arrhenius equation k(s-1) = 1015.30 +/- 0.24exp(-226 +/- 3 kJ/mol RT) Diethyl propargyl amine decomposed cleanly into allene and N-ethyl ethanaldimine.The first-order rate coefficients for allene formation fit the Arrhenius equation k(s-1) = 1012.84 +/- 0.30exp(-168 +/- 4 kJ/mol RT).The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six-center cyclic transition states.For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed.
- Martin, Gonzalo,Ascanio, Julian,Rodriguez, Jesus
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- Electronic Structure and Gas-Phase Thermolysis of 2-Tetrazenes with Acyclic or Cyclic Amino Groups Studied by Photoelectron Spectroscopy
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The electronic structures and the gas-phase thermolysis of the 2-tetrazenes 2-13 have been studied by He(I) photoelectron spectroscopy.The compounds are characterized by at least three ionization potentials with energies less than 10 eV which are assigned to the molecular orbitals ?3 (HOMO), n(+), ?2, and n(-).In the thermolyses either the formal disproportionation products (amine and imine) of the respective aminyl radical are found, or the latter is stabilized by loss of an alkyl radical affording also an imine.Further products which can be explained by radical reactions are detected in flash vacuum pyrolyses.The tricyclic cis-2-tetrazene 13 is cleaved by cycloreversion.The methoxymethylsubstituted compound 8 exhibit a more complex cleavage pattern. - Key Words: Electronic structure / PE spectroscopy / Thermolysis, gas-phase / Imines / Radicals
- Rademacher, Paul,Heymanns, Peter,Muenzenberg, Ralf,Woell, Heike,Kowski, Klaus,Poppek, Rainer
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p. 2073 - 2080
(2007/10/02)
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- Thermolysis of N-alkylated ethylenediamines: an ultraviolet photoelectron spectroscopy study
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Thermolyses of N,N,N',N'-tetramethylethylenediamine(1a),N,N,N',N'-tetraethylethylenediamine (1b) and sym-N,N'-dimethylethylenediamine (1c) at 760-825 deg C have been studied by ultraviolet photoelectron spectroscopy.Although the corresponding N -alkylated aminomethylene radicals were not observed, this study establishes that termolysis of 1a is an efficient route to N-methylenimine (3a); methane, ethane, and ethene are the other major products.Diamine 1b yields, besides ethane, ethene, and propane, heretofore unreported N-ethylmethylenimine (3b).Diamine 1c yields imine 3a and methylenimine (3c), as well as hydrogen, methane, ethane, ethene.Molecular orbital eigenvalues of the imines are calculated using HAM/3, MNDO, HF/STO-3G, HF/3-21* methods.
- Werstiuk, N. H.
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p. 2175 - 2183
(2007/10/02)
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