- Kinetic and Theoretical Study of the Nitrate (NO3) Radical Gas Phase Reactions with N-Nitrosodimethylamine and N-Nitrosodiethylamine
-
The reaction rates of (CH3)2NNO and (CH3CH2)2NNO with NO3 radicals were determined relative to formaldehyde (CH2O) and ethene (CH2CH2) at 298 ± 2 K and 1013 ± 10 hPa in purified air by long path FTIR spectroscopy. The reactions are too slow to be of importance at atmospheric conditions: k NO3+(CH3)2NNO = (1.47 ± 0.23) × 10-16 and k NO3+(CH3CH2)2NNO = (5.1 ± 0.4) × 10-16 cm3 molecule-1 s-1 (1σ error limits). Theoretical calculations, based on CCSD(T?)-F12a/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ results, predict the corresponding imines as the sole primary products in nitrosamine reactions with NO3 and OH radicals.
- Maguta, Mihayo Musabila,Stenstr?m, Yngve,Nielsen, Claus J.
-
-
Read Online
- Photolysis of Dimethylnitrosamine in the Gas Phase
-
Photodecomposition of dimethylnitrosamine in the gas phase ( 1 Torr) has been investigated following irradiation into the S1(n?*) 0(363.5 nm) and S2(??'*) 0(248.1 nm) transitions at room temperature.With a quantum yield of unity, excitation into the S1 state yields the fragments (CH3)2N and NO which then recombine leaving no photoproducts.The addition of O2 results in only one photoproduct, (CH3)2NNO2.Irradiating into the S2 state, the products CH2=N-CH3, (CH2=N-CH3)3, CH2=NOH, N2O, NO, H2, and N2 were identified by capillary gas chromatography mass spectrometry.In the presence of N2 as a buffer gas the photoproducts are only CH2=N-CH3, (CH2=N-CH3)3, N2O, and H2.For both excitation conditions a mechanism is proposed involving cleavage of the N,N-bond as the main primary photolytic process.
- Geiger, Georg,Huber, J. Robert
-
-
Read Online
- Electron diffraction study of thermal decomposition products of trimethylamine: molecular structure of CH3-N=CH2
-
Structural studies of thermal decomposition products of trimethylamine have been performed by gas electron diffraction aided by mass spectrometry.Trimethylamine vapor is heated in a quartz tube shortly before the nozzle tip which is kept at room temperature.When the temperature inside the quartz tube is 515 deg C, N(CH3)3 simply decomposes into CH4 and short-lived CH3-N=CH2.However, more complicated reactions, which include CH3-N=CH2->CH4+HCN, take place at the reaction temperature of 535 deg C.The zero-point average structure of N-methylmethyleneimine (CH3-N=CH2) has been determined by a joint analysis of electron diffraction data and rotational constants, and then compared with ab initio calculations.Principal structural parameters are as follows: rz(N=C)=1.279(6) Angstroem, rz(N-C)=1.458(8) Angstroem and Θz(CNC)=116.62(12) deg.The molecular structure of trimethylamine has been determined much more precisely than that given in the literature.
- Fujiwara, Hideo,Egawa, Toru,Konaka, Shigehiro
-
-
Read Online
- Ultraviolet photoelectron studies of dehydration and dehydrohalogenation reactions of β-substituted alcohols using H-ZSM-5 and the formation of unstable intermediates
-
Dehydration of 1,2-ethanediol and 2-aminoethanol and dehydrohalogenation of 2-chloro- and 2-fluoroethanol over H-ZSM-5 at 200-350°C was followed under low-pressure (ca. 25 mTorr) flow conditions using ultraviolet photoelectron spectroscopy as a direct on-line monitor. This circumvents the necessity of separations since the effluent from the reactor can be monitored immediately after leaving the catalyst bed. Under these conditions all precursors are consumed, leading to the final product acetaldehyde, except in the case of 2-aminoethanol where dehydration gives, in high yield, the unexpected N-methyl isomer of methylenimine, an unstable molecule. A postulated mechanism for this result, applicable also to the formation of acetaldehyde in the other β-substituted alcohols, suggests the intermediacy of three-membered cyclic species, namely, ethylenimine and ethylene oxide or their protonated analogs.
- Alaee,Westwood
-
-
Read Online
- Too Short-Lived or Not Existing Species: N-Azidoamines Reinvestigated
-
Treatment of N-chlorodimethylamine with sodium azide in dichloromethane does not lead to N-azidodimethylamine, as thought for more than 50 years. Instead, surprisingly, (azidomethyl)dimethylamine is generated with good reproducibility. A plausible reaction mechanism to explain the formation of this product is presented. The reaction of lithium dibenzylhydrazide with tosyl azide does not result in the creation of an N-azidoamine, which can be detected by IR spectroscopy at ambient temperature, as it was claimed previously. Additional experiments with diazo group transfer to lithium hydrazides show that intermediate N-azidoamines are very short-lived or their formation is bypassed by direct generation of 1,1-diazenes via synchronous cleavage of two N-N bonds.
- Banert, Klaus,Pester, Tom
-
p. 4033 - 4039
(2019/04/10)
-
- Matrix-IR spectroscopic investigations of the thermolysis and photolysis of diazoamides
-
Matrix photolysis of N,N-dialkyldiazoacetamides 1a-d at 7-10 K results in either the formation of C-H insertion products (in case of N,N-dimethyl and N,N-diethyl diazoamides) or almost exclusive Wolff rearrangement to ketenes (in the case of the cyclic di
- Wentrup, Curt,Bibas, Herve,Kuhn, Arvid,Mitschke, Ullrich,McMills, Mark C.
-
p. 10705 - 10717
(2013/11/19)
-
- Nickel-catalyzed transfer semihydrogenation and hydroamination of aromatic alkynes using amines as hydrogen donors
-
The transfer hydrogenation of diphenylacetylene to yield cis- and trans-stilbenes was achieved using a variety of amines as hydrogen donors and the complex 1 ([(dippe)Ni(μ-H)]2) in catalytic amounts (0.5% mol). The use of nucleophilic amines such as pyrrolidine in neat conditions afforded the hydroamination of diphenylacetylene, in moderate to high yields. Cyclization of 2-ethynylaniline also was carried out under similar conditions, with 1 in catalytic amounts, but in low yield, mainly due to the formation of homocoupling products of the starting material. The hydrogenation of diphenylacetylene by using other nitrogenated compounds such as aromatic N-heterocycles was addressed to give a metal-mediated process, using 1 in stoichiometric amounts.
- Reyes-Sanchez, Adan,Canavera-Buelvas, Farrah,Barrios-Francisco, Rigoberto,Cifuentes-Vaca, Olga L.,Flores-Alamo, Marcos,Garcia, Juventino J.
-
experimental part
p. 3340 - 3345
(2011/08/22)
-
- A small molecule that mimics the metabolic activity of copper-containing amine oxidases (CuAOs) toward physiological mono- and polyamines
-
Primary aliphatic biogenic amines have been successfully oxidized using a quinonoid species that mimics the metabolic activity of copper-containing amine oxidase (CuAO) enzymes. Especially, high catalytic performances were observed with aminoacetone, a threonine catabolite, and methylamine, a metabolite of adrenaline, and with the primary amino groups of putrescine and spermidine which are both decarboxylation products of ornithine and S-adenosyl-methionine. Furthermore, contrary to flavine adenine dinucleotide (FAD)-dependent amine oxidase enzymes, no activity was found toward secondary and tertiary amines.
- Largeron, Martine,Fleury, Maurice-Bernard,Strolin Benedetti, Margherita
-
supporting information; experimental part
p. 3796 - 3800
(2010/09/06)
-
- GASEOUS DIELECTRICS WITH LOW GLOBAL WARMING POTENTIALS
-
A dielectric gaseous compound which exhibits the following properties: a boiling point in the range between about ?20° C. to about ?273° C.; non-ozone depleting; a GWP less than about 22,200; chemical stability, as measured by a negative standard enthalpy of formation (dHf0); a toxicity level such that when the dielectric gas leaks, the effective diluted concentration does not exceed its PEL; and a dielectric strength greater than air.
- -
-
-
- Retro-Ene Reactions in Acylallene Derivatives
-
Allenic esters and amides 4 undergo a retro-ene reaction to vinylketene (6) and an aldehyde or imine (5) under the conditions of flash vacuum thermolysis (FVT). The same products are obtained by FVT of cyclobutenones 7 via electrocyclic ring opening to alkoxy- or aminovinylketenes 3 and 1,3-rearrangement of ketenes 3 to allenes 4. All the intermediates and products were characterized by matrix isolation IR spectroscopy, and in the case of 4c the reaction was also monitored by online mass spectrometry. A lower temperature for the retro-ene reaction of 4c, eliminating an imine, than for 4a, eliminating formaldehyde, is in agreement with a lower calculated activation barrier (167 and 181 kJ mol-1, respectively, at the G2(MP2,SVP) level of theory). The allenic amide 11 undergoes an analogous retro-ene reaction to the (unobserved) vinylketene 13, the latter isomerizing to cyclohexenylacrolein 16 in a 1,5-H shift (calculated barrier 125 kJ mol-1; G2 (MP2, SVP)).
- Bibas, Herve,Koch, Rainer,Wentrup, Curt
-
p. 2619 - 2626
(2007/10/03)
-
- Thermal Decomposition of Lithium Amides: a Matrix Isolation Investigation
-
Lithium dimethylamide, lithium diethylamide and lithium diisopropylamide decompose, probably via an αβ-lithium hydride elimination mechanism, to give N-methylenemethylamine.N-ethylideneethylamine and N-isopropylideneisopropylamine, respectively.Lithium dibenzylamide and lithium bis(trimethylsilyl)amide exhibited different behaviour.Lithium dibenzylamide decomposes via the rupture of carbon-nitrogen and carbon-carbon bonds, to give toluene and benzene, and lithium bis (trimethylsilyl)amide volatilizes without decomposition.
- Withnall, Robert,Dunkin, Ian R.,Snaith, Ronald
-
p. 1973 - 1978
(2007/10/02)
-
- Absolute Rates of Recombination and Disproportination of Dimethylaminyl Radicals
-
The absolute rate constants for the recombination (kr) and disproportionation (kd) reactions of dimethylaminyl radicals were determined at room temperature with the very low pressure reactor (VLPR) technique.The obtained values were kr = (1.70 +/- 0.19) x 1E-12 cm3 molecule-1 s-1 and kd = (4.19 +/- 0.52) x 1E-12 cm3 molecule-1 s-1, and the ratio kd/kr was 2.32 +/- 0.26.The transition-state geometries for both recombination and disproportination reactions are loose, with the N...N bond length ca. 3.5 Angstroem and the N...H...C distance ca. 4.4 Angstroem.In the recombination TS, the four C-N...N bending modes are ca. 90 cm-1 and play a significant role in the formation of the N-N bond in tetramethylhydrazine.In the disproportionation TS, the two (in-plane and out-of-plane) vibrational modes of the metathetic hydrogen are ca. 110 cm-1 and are essential in the formation of the N-H bond in dimethylamine.
- Lazarou, Yannis G.,Papagiannakopoulos, Panos
-
p. 9133 - 9140
(2007/10/02)
-
- Thermal Decomposition of Dimethylnitramine and Dimethylnitrosamine by Pulsed Laser Pyrolysis
-
Pyrolysis of dimethylnitramine (DMNA) and dimethylnitrosamine (DMNO) was carried out in a flow system over the temperature range 800-900 K using pulsed infrared laser heating, via SF6 in a 250-Torr bath of CO2 and radical scavanger.Arrhenius parameters for DMNO and DMNA composition were log k(s-1)=(15.8+/-1.1)-(50.0+/-3.4)/2.3RT and (13.5+/-0.6)-(37.4+/-2.5)/2.3RT, respectively.The former set of parameters is consistentwith simple bond scission as the rate-limiting step; the latter set, which was produced with different scavengers, temperature standards, and varying amounts of added NO as a radical trap, is not consistent with simple bond scission.The experimental reaults can be reproduced via a mechanistic numerical model in which N-NO2 bond scission and nitro-nitrite rearrangement are competitive initial steps and the displacement of NO2 from DMNA by NO is included as a low-temperature route to DMNO.
- Nigenda, S. Esther,McMillen, Donald F.,Golden, David M.
-
p. 1124 - 1130
(2007/10/02)
-
- SYNTHESE D'IMINES LINEAIRES NON-STABILISEES PAR REACTIONS GAZ-SOLIDE SOUS VIDE(1).
-
Unstabilized imines are synthetized in gram-scale by vacuum dehydrochlorination of N-chloroalkylamines and by vacuum dehydrocyanation of α-aminonitriles on solid base.All the new compounds are characterized at low temperature by 1H, 13C NMR and IR spectroscopy.
- Guillemin, Jean-Claude,Denis, Jean-Marc
-
p. 4431 - 4446
(2007/10/02)
-
- Gas-phase Pyrolysis of Methyl Dimethylcarbamate and the Correponding Mono- and Dithio Analogs
-
Gas-phase pyrolysis of methyl dimethylcarbamate (1), O-methyl dimethylthiocarbamate (2), S-methyl dimethylthiocarbamate (3), and methyl dimethyldithiocarbamate (4) has been carried out in the temperature range 1043-1404 K applying the gas-phase Curie-point pyrolysis technique.Real-time analysis of the pyrolyses were carried out by field ionization- and collision activation mass spectrometry. 1 and 4 were found to be thermally very stable even after pyrolysis at 1404 K.N-Methyl methanimine was found in moderate yield following pyrolysis of 2 and 3.The possible isomerization of the ester functions were studied by application of collision activation mass spectrometry in combination with 18O and 34S labeling.The results are discussed considering available data on the simple acetic acid esters with special emphasis on the effect of increasing sulfur content.
- Carlsen, Lars,Egsgaard, Helge
-
p. 987 - 990
(2007/10/02)
-
- Gasphase Reactions, 60. - Methanimines RR'C=NR'': Preparation and Photoelectron Spectra
-
Methanimines RR'C=NR'' (R, R', R'' = H, CH3) are prepared by pyrolysis of alkyl azides, or by consecutive chlorination of gaseous alkylamines at solid N-chlorosuccinimide and dehydrochlorination of the resulting N-chloroamines by passage over potassium tert-butylate in flow reactors; the reaction conditions are advantageously optimized applying PE spectroscopic realtime analysis.Their ionization patterns are assigned based on geometry-optimized MNDO calculations, radical cation state comparison, and the vibrational fine structures of individual bands.Despite their tendency to polymerize, the compounds may be condensed as monomers at low temperature and characterized by NMR.Reevaporated methanimine decomposes into H2 and HCN only above 1300 K, i.e. relative to its formation as "chemically activated" product in the methyl azide pyrolysis at a temperature higher by over 500 K.The chlorination of cyclopropylamine followed by dehydrochlorination yields a reaction mixture containing large amounts of hitherto unknown cyclopropanimine (H2C)2C=NH.
- Bock, Hans,Dammel, Ralph
-
p. 1961 - 1970
(2007/10/02)
-
- Thermolysis of N-alkylated ethylenediamines: an ultraviolet photoelectron spectroscopy study
-
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.
-
p. 2175 - 2183
(2007/10/02)
-
- ELECTRONIC STRUCTURES AND THERMOLYSES OF 2-TETRAZENES
-
The electronic structures and gas phase termolyses of the cyclic 2-tetrazenes 2 and 3 of open chain 1,1,4,4-tetramethyl-2-tetrazene (1) have been studied by photoelectron spectroscopy.While the six-membered ring compound 2 yields 1-methylmethylenamine (6) and nitrogen as fragments, the seven-membered ring compound 3 is contracted to 1,2-dimethylpyrazolidine (11).The acyclic 2-tetrazene 1 prefers disproportionation to 6 and dimethylamine (7).Based on MNDO calculations the ionization potentials of 1 - 3 were assigned to molecular orbitals.Several conformations of 2 and 3 were calculated.Compound 2 shows a rigid boat conformation with equatorial methyl groups, while 3 can occupy several conformations of similar energies.The different thermal decompositions of 1 - 3 are explained.
- Heymanns, Peter,Rademacher, Paul
-
p. 2511 - 2518
(2007/10/02)
-
- MATRIX ISOLATION AND IR SPECTROSCOPIC STUDY OF THE PYROLYSIS PRODUCTS OF 2-METHYL-3,4-DIAZAPENTA-1,3-DIENE. CLEAVAGE OF N=N-BOND IN UNSATURATED AZO COMPOUNDS
-
Under very low-pressure pyrolysis (VLPP) conditions the decomposition of 2-methyl-3,4-diazapenta-1,3-diene proceeds via: (a) homolytic cleavage of C-N-bonds with the formation of methyl and 1-methylvinyl radicals (1); (b) cleavage of double N=N-bond with the formation of N-methyl methyleneimine (3) and acetonitrile.A mechanism involving decomposition of the intermediate 1,4-diazacyclobutene has been suggested for (b).
- Ziegler, U.,Zimmermann, G.,Ondruschka, B.,Volkova, V. V.,Gusel'nikov, L. E.,et al.
-
p. 5825 - 5828
(2007/10/02)
-
- Flash Vacuum Thermolysis of α-Aminonitriles and Subsequent HCN Removal on Solid Base, a 'One Line' Multistep Sequence to Reactive N-Methyleneamines
-
Reactive methyleneamines bearing alkyl or functional groups are isolated at low temperature in the condensate state by flash vacuum thermolysis of α-aminonitriles and subsequent vapour phase HCN removal on solid base.
- Guillemin, J. C.,Denis, J. M.
-
p. 951 - 952
(2007/10/02)
-
- Retro-ene Reactions and 2-Alkylidenepyrrolidine Formation from Thermolyses of β-Amino-olefins and β-Aminoacetylenes
-
Thermolyses of β-aminoacetylenes with a terminal acetylenic bond and of β-amino-olefins afford retro-ene reactions in which nitrogen acts as the hydrogen donor, whereas alkyl substitution on the terminus of the acetylenic bond leads to a novel, facile cyclization to a 2-alkylidenepyrrolidine.
- Viola, Alfred,Locke, John S.
-
p. 1429 - 1431
(2007/10/02)
-