1070-71-9Relevant articles and documents
Pyrolysis of Acrylonitrile at Elevated Temperatures. Studies with a Single-Pulse Shock Tube
Lifshitz, Assa,Bidani, Menashe,Suslensky, Aya,Tamburu, Carmen
, p. 1369 - 1373 (1989)
The thermal decomposition of acrylonitrile was studied behind reflected shocks in a single-pulse shock tube over the temperature range 1150-1430 K and overall densities of ca. 3 X 10-5 mol/cm3.Under these conditions the major reaction products are (1) hydrogen cyanide and acetylene and (2) hydrogen and cyanoacetylene: CH2=CHCN -> CH*CH + HCN (reaction 1) and CH2=CHCN -> CH*C-CN + H2 (reaction 7).In the presence of toluene, at a ratio of 0/0 ca. 10/1, a twofold decrease in the production rate of these products was observed, indicating a free-radical mechanism in parallel to the four-center eliminations.After the contribution of the free radical chain was subtracted, the following rate constants for the four-center eliminations were obtained: k1 = 1012.25 exp (-68 X 103/RT) s-1, and k2 = 1013.40 exp (-77 X 103/RT) s-1, where activation energies are expressed in units cal/mol.Ethylene was found in quantities roughly equal to those of cyanoacetylene.C2N2, CH3CN, CH4, C4H6 and C2H6 were found in the postshock mixtures but at much lower concentrations.Arrhenius parameters for the formation rate of the different reaction products are given and the general pyrolysis mechanism is discussed.
Pyrolyses of aromatic azines: Pyrazine, pyrimidine, and pyridine
Kiefer,Zhang,Kern,Yao,Jursic
, p. 7061 - 7073 (1997)
The thermal decompositions of pyrazine, pyrimidine, and pyridine in shock waves have been investigated using the complementary techniques of laser-schlieren (LS) densitometry and time-of-flight (TOF) mass spectrometry (1600-2300 K, 150-350 Torr). A free radical chain reaction with initiation by ring C-H fission in the pyrolyses of all three azines is proposed. The measured C-H fission rates are compared and analyzed by RRKM theory. Barriers of 103 ± 2 kcal/mol for pyrazine, 98 ± 2 for pyrimidine, and 105 ± 2 for pyridine have been determined, supporting values lower than the barrier for C-H fission in benzene, 112 kcal/mol. The lower barriers for the azines are explained by the additional contributions of resonance structures of azyl radicals due to neighboring N-C interactions, which serve to further stabilize the azyl radicals. Detailed chain mechanisms are constructed to model the LS profiles and the TOF concentration profiles of the major products, hydrogen cyanide, acetylene, cyanoacetylene, and diacetylene. Of particular interest are the TOF observations and the mechanistic explanation of temperature dependent maxima seen in the formation of cyanoacetylene in the presence or absence of excess H2.
The pyrolysis of 3-picoline: Ab initio quantum chemical and experimental (shock tube) kinetic studies
Jones, Jeffrey,Bacskay, George B.,Mackie, John C.
, p. 239 - 248 (1996)
The pyrolysis of 3-picoline dilute in argon was investigated using a single-pulse shock tube over the temperature range of 1400-1650 K and total pressures of 12-13 atm. The principal products observed were HCN, acetylene, benzene, cyanoacetylene, methane, and pyridine. Assuming that 3-picoline decomposes according to first-order kinetics, the rate constant for its overall disappearance was determined to be kdis = 1016.9(±0.8) exp[-99 (±6) kcal mol-1/RT] s-1. The principal initial decomposition routes were found to be via the formation of the 3-picolyl and m-pyridyl radicals whose subsequent ring-opening led to the observed products. A 68-step kinetic model was developed that successfully fits the experimental data. The dominant reactions, i.e., the formation of picolyl and pyridlyl radicals and their subsequent chain-opening reactions, were studied using ab initio quantum chemical techniques. The ab initio data were also incorporated into the kinetic model in the form of energies and A-factors for reactions for which no kinetic or thermochemical data were previously available. Optimization of the kinetic model yields a value of 64 ± (3) kcal mol-1 for the heat of formation of 3-picolyl, a value lower than that for 2-picolyl, suggesting that the decomposition of 3-picoline more closely resembles that of toluene, rather than its isomer 2-picoline.
Photodissociation of acrylonitrile at 193 nm: A photofragment translational spectroscopy study using synchrotron radiation for product photoionization
Blank, David A.,Suits, Arthur G.,Lee, Yuan T.,North, Simon W.,Hall, Gregory E.
, p. 5784 - 5794 (1998)
We have investigated the photodissociation of acrylonitrile (H2CCHCN) at 193 nm using the technique of photofragment translational spectroscopy. The experiments were performed at the Chemical Dynamics Beamline at the Advanced Light Source and used tunable vacuum ultraviolet synchrotron radiation for product photoionization. We have identified four primary dissociation channels including atomic and molecular hydrogen elimination. HCN elimination, and CN elimination. There is significant evidence that all of the dissociation channels occur on the ground electronic surface following internal conversion from the initially optically prepared state. The product translational energy distributions reflect near statistical simple bond rupture for the radical dissociation channels, while substantial recombination barriers mediate the translational energy release for the two molecular elimination channels. Photoionization onsets have provided additional insight into the chemical identities of the products and their internal energy content.
Shock Tube Pyrolysis of Pyridine
Mackie, John C.,Colket III, Meredith B.,Nelson, Peter F.
, p. 4099 - 4106 (1990)
The kinetics of pyridine dilute in argon have been studied in a single-pulse shock tube, using cappilary column GC together with GC/MS and FTIR spectroscopy for product determination, over the temperature range of 1300-1800 K and total pressures of 7-11 atm.At the lower end of the studied temperatures, cyanoacetylene was found to be the principal nitrogen-containing product.At elevated temperature hydrogen cyanide predominated.Other major products were acetylene and hydrogen.Thermochemical estimates of the isomeric cyclic pyridyls produced in the pyrolysis indicate that the ortho isomer is unique in being able to undergo facile cleavage to an open-chain cyano radical from which cyanoacetylene is produced.Several sources of HCN were identified in the system.The m- and p-pyridyls may eliminate HCN in a molecular process.An important source of HCN at high temperatures is the addition of H-atoms to cyano compounds, especially cyanoacetylene, but also acetonitrile and acrylonitrile which are produced in the pyrolysis.The pyrolysis is a chain process initiated principally by C-H bond fission to form o-pyridyl.A 58-step reaction model is presented and shown to substantially fit the observed profiles of the major product species.From this model we derive a value for the rate constant of the principal initiation reaction, C5H5N --> o-C5H4N + H (1), of k1=1015.9+/-0.4exp(-98 +/- 3 kcal mol-1/RT)s-1 between 1300 and 1800 K and at a total pressure of about 10 atm.
Kinetics of Thermal Decomposition of the Diazines: Shock-tube Pyrolysis of Pyrimidine
Doughty, Alan,Mackie, John C.
, p. 541 - 548 (1994)
The kinetics of pyrolysis of pyrimidine diluted in argon have been studied behind reflected shock waves over the temperature range 1200-1850 K, at uniform gas residence times of 850-1000 μs and pressures of 13-15 atm.The major products of pyrimidine pyrolysis were found to be acetylene, HCN, acrylonitrile, cyanoacetylene and H2.Using both end-product analysis and real-time UV spectrometry the kinetics of pyrimidine disappearance were found to be first order with respect to reactant concentration over the concentration range of 0.07-0.3 molpercent.The two techniques yielded a first-order rate constant (kdis) for the disappearance of pyrimidine given by the expression 1012.3(+/-0.4)exp-1/RT>s-1.A detailed reaction model incorporating a free-radical mechanism for the decomposition of pyrimidine has been developed, and shown to predict the reactant and product concentrations between 1250 and 1600 K.Important radicals in the mechanism were found to be o- and p-pyrimidyl, with H atoms and CN radicals being radical chain carriers.Sensitivity and flux analysis of the kinetic model has shown the most important initiation pathway to be the loss of an H atom from pyrimidine to yield o-pyrimidyl.Optimisation of the Arrhenius parameters for this initiation reaction yields an activation energy cosistent with a heat of formation of the o-pyrimidyl radical of 376(+/-10) kJ mol-1.
Total Synthesis of Aetokthonotoxin, the Cyanobacterial Neurotoxin Causing Vacuolar Myelinopathy
Ricardo, Manuel G.,Schwark, Markus,Llanes, Dayma,Niedermeyer, Timo H. J.,Westermann, Bernhard
, p. 12032 - 12035 (2021)
Aetokthonotoxin has recently been identified as the cyanobacterial neurotoxin causing Vacuolar Myelinopathy, a fatal neurologic disease, spreading through a trophic cascade and affecting birds of prey such as the bald eagle in the USA. Here, we describe the total synthesis of this specialized metabolite. The complex, highly brominated 1,2’-biindole could be synthesized via a Somei-type Michael reaction as key step. The optimised sequence yielded the natural product in five steps with an overall yield of 29 %.
Photochemistry of Acetylene, Hudrogen Cyanide, and Mixtures
Becker, Ralph S.,Hong, J. H.
, p. 163 - 166 (1983)
Photoluses of HCN, C2H2, and mixtures were accomplished including various ratios of HCN/C2H2 and time periods.The photolysis of HCN yielded (CN)2, CH4, NH3, CH3NH2, (NH)2, and a brown polymer.The products from C2H2 were diacetylene (C4H2), C2H4, C6H6, vinylacetylene, phenylacetylene, and a polymer.Products from a relatively low HCN/C2H2 ratio (5:1) where 90percent of the light is absorbed by C2H2 were similar to those of C2H2 except for the additional formation of acrylonitrile (C2H3CN).At relatively higher ratios of HCN/C2H2 where 37-56percent of the light is absorbed by HCN, cyanoacetylene (C2HCN) was formed in addition to the foregoing products and the C4H2 substantially reduced.The proposed principal path for formation of C4H2 is attack of C2H. on C2H2, while for C2H3CN the principal path is attack of C2H3. on HCN.The proposed principal path for production of C2HCN is via CN. attack on C2H2.Several products from HCN are proposed to be the result of progressive H atom addition.Other products from C2H2 and HCN are the result of radical-radical recombination.We believe these results could have relevance to Jovian atmosphere chemistry and formation of several molecules found in interstellar space.
The microwave spectrum of cyanophosphaacetylene, H2P{single bond}C{triple bond, long}C{single bond}C{triple bond, long}N
Kang, Lu,Minei, Andrea J.,Novick, Stewart E.
, p. 255 - 259 (2006)
The a type transitions of the microwave rotational spectra of cyanophosphaacetylene, H2P{single bond}C{triple bond, long}C{single bond}C{triple bond, long}N, have been investigated in the frequency region between 5 and 26.5 GHz by Fourier transformation microwave (FTMW) spectroscopy. Rotational, centrifugal distortion and 14N nuclear quadrupole coupling constants have been determined. Density functional theory level ab initio calculations were performed to predict the molecular constants, and the predicted values are in good agreement with our experimentally determined results. The 13C and 15N isotopomer transitions were also observed. The derived r0 structure is quite comparable to the calculated H2P{single bond}C{triple bond, long}C{single bond}C{triple bond, long}N equilibrium geometry.
Kinetics of Pyrolysis of a Coal Model Compound, 2-Picoline, the Nitrogen Heteroaromatic Analogue of Toluene. 1. Product Distributions
Terentis, Andrew,Doughty, Alan,Mackie, John C.
, p. 10334 - 10339 (1992)
The pyrolysis of 2-picoline in dilute mixtures with argon has been investigated using the single-pulse shock tube and was found to decompose over the temperature range 1300-1550 K, at an average residence time of 800 μs and uniform pressure of 14-16 atm.The major products observed were acetylene, methane, hydrogen, HCN, and cyanoacetylene.Over the studied range of mixture compositions (0.06-0.20 molpercent of 2-picoline) the overall rate of disappearance of 2-picoline obeyed first-order kinetics.Arrhenius parameters for disappearance of picoline were found to be Adis=1017.4+/-1.1 s-1 and Ea,dis=98+/-7 kcal mol-1.From the distribution of observed products it is concluded that the principal initiation reactions were analogous to those known to occur in toluene, the hydrocarbon analogue of 2-picoline, and were found to be C-C bond fission to yield o-pyridyl and methyl radicals and C-H fission to yield H atoms and 2-picolyl, the N-containing analogue of benzyl.Major products were observed from decomposition of both the o-pyridyl and the 2-picolyl radicals.Cyanoacetylene arises principally from the secondary reactions of o-pyridyl.A product with m/z 91 was observed at the lowest temperatures at which 2-picoline decomposition could be detected.It has been identified as 1-cyanocyclopentadiene and arises from loss of H from the 2-picolyl radical.Other products arising from secondary decomposition of 2-picolyl at higher temperatures include HCN and cyclopentadienyl radicals.
