- The crystal structure of carbamoyl fluoride, NH2COF
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Although first synthesized in 1940, the X-ray crystal structure of carbamoyl fluoride, NH2COF, has until now remained unknown. [1] NH2COF crystallizes in the orthorhombic space group Ibam, is planar, and exhibits a short C-N bond length, 1.3168(13) ?, implying a significant degree of donation from the nitrogen lone pair. The structure features one molecule in the asymmetric unit and eight molecules in the unit cell. There are four molecules in two planar layers that are connected by a network of NH·O hydrogen bonds with N·O distances of 2.987(2) ? and 2.945(2) ?. The compound was also studied by quantum chemical calculations at both the ab initio (MP2) and density functional theory (B3LYP) level.
- Baxter, Amanda F.,Christe, Karl O.,Haiges, Ralf
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- The hydroxide-assisted hydrolysis of cyanogen chloride in aqueous solution
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The hydrolysis of cyanogen chloride (ClCN) was studied as a function of temperature and pH. Results were used to resolve discrepancies among previously reported kinetic constants. The pH dependence was studied over a range of 9.54-10.93 at a temperature of 21.0°C. The effect of temperature was investigated over the range of 10-30°C at a pH of approximately 10. Changes in the concentrations of ClCN and the reaction products cyanic acid and chloride ion were monitored with time. For the conditions corresponding to these experiments, the hydroxide-assisted hydrolysis pathway predominated. Collision frequency factor and activation energies recommended to represent the hydrolysis of ClCN in aqueous solution are A=2.06x1011M-1s-1 and E(a)=60,980Jmol-1 for the hydroxide-ion-assisted reaction, and A=9.97x108s-1 and E(a)=87,180Jmol-1 for the water-assisted reaction. Copyright (C) 2001 Elsevier Science Ltd. The hydrolysis of cyanogen chloride (ClCN) was studied as a function of temperature and pH. Results were used to resolve discrepancies among previously reported kinetic constants. The pH dependence was studied over a range of 9.54-10.93 at a temperature of 21.0 °C. The effect of temperature was investigated over the range of 10-30 °C at a pH of approximately 10. Changes in the concentrations of ClCN and the reaction products cyanic acid and chloride ion were monitored with time. For the conditions corresponding to these experiments, the hydroxide-assisted hydrolysis pathway predominated. Collision frequency factor and activation energies recommended to represent the hydrolysis of ClCN in aqueous solution are A = 2.06×1011 M-1 s-1 and Ea = 60,980 J mol-1 for the hydroxide-ion-assisted reaction, and A = 9.97×108 s-1 and Ea = 87,180 J mol-1 for the water-assisted reaction.
- Pedersen III,Marinas
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- Thermal reactivity of HNCO with water ice: An infrared and theoretical study
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The structure and energy of the 1:1 complexes between isocyanic acid (HNCO) and H2O are investigated using FTIR matrix isolation spectroscopy and quantum calculations at the MP2/6-31G(d,p) level. Calculations yield two stable complexes. The first and most stable one (ΔE = 23.3 kJ/mol) corresponds a form which involves a hydrogen bond between the acid hydrogen of HNCO and the oxygen of water. The second form involves a hydrogen bond between the terminal oxygen of HNCO and hydrogen of water. In an argon matrix at 10 K, only the first form is observed. Adsorption on amorphous ice water at 10 K shows the formation of only one adsorption site between HNCO and ice. It is comparable to the complex observed in matrix and involves an interaction with the dangling oxygen site of ice. Modeling using computer code indicates the formation of polymeric structure on ice surface. Warming of HNCO, adsorbed on H2O ice film or co-deposited with H2O samples above 110 K, induces the formation of isocyanate ion (OCN-) characterized by its vasNCO infrared absorption band near 2170 cm-1. OCN- can be produced by purely solvation-induced HNCO dissociative ionization. The transition state of this process is calculated 42 kJ/mol above the initial state, using the ONIOM model in B3LYP/6-31g(d,p).
- Raunier, Sébastien,Chiavassa, Thierry,Allouche, Alain,Marinelli, Francis,Aycard, Jean-Pierre
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- Reaction of cyanomethylene with nitric oxide and oxygen at 298 K: HCCN + NO, O2
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The reactions of the cyanomethylene (HCCN) radical with nitric oxide (NO) and with molecular oxygen (O2) have been investigated using infrared kinetic spectroscopy. The overall second-order rate constant for each reaction has been determined using pseudo-first-order methods yielding (3.5 ± 0.6) × 10-11 cm3 molecule-1 s-1 for the reaction with NO and (1.8 ± 0.4) × 10-12 cm-3 molecule-1 s-1 for the reaction with O2. For each reaction, several products were observed, but none were quantified. Hydrogen cyanide (HCN) and fulminic acid (HCNO) were observed as products of the reaction with NO. For the reaction with O2, HCN, hydrogen isocyanide (HNC), and carbon dioxide (CO2) were observed. Species searched for but not detected from either reaction include isocyanic acid (HNCO), cyanic acid (HOCN), formyl (HCO) radical, isofulminic acid (HONC), hydroxyl radical (OH), and ethynyl radical (C2H). In addition, NO was searched for, but not observed, as a product of the O2 reaction. On the time scale of our experiments, no reaction between HCCN and any of the following species was observed (k -13 cm3 molecule-1 s-1): methane (CH4), CO2 acetylene (C2H2), ethylene (C2H4), carbon monoxide (CO), and hydrogen (H2).
- Adamson,DeSain,Curl,Glass
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- Determination of the rate constant and product channels for the radical-radical reaction NCO(X 2Π) + C2H5(X 2A″) at 293 K
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The rate constant and product branching ratios for the reaction of the cyanato radical, NCO(X 2Π), with the ethyl radical, C 2H5(X 2A″), have been measured over the pressure range of 0.28 to 0.59 kPa and at a temperature of 293 ± 2 K. The total rate constant, k1, increased with pressure, P(kPa), described by k1 = (1.25 ± 0.16) × 10-10 + (4.22 ± 0.35) × 10-10 P cm3 molecule-1 s-1. Three product channels were observed that were not pressure dependent: (1a) HNCO + C2H4, k1a = (1.1 ± 0.16) × 10-10, (1b) HONC + C2H4, k1b = (2.9 ± 1.3) × 10-11, (1c) HCN + C 2H4O, k1c = (8.7 ± 1.5) × 10 -13, with units cm3 molecule-1 s-1 and uncertainties of one-standard deviation in the scatter of the data. The pressure dependence was attributed to a forth channel, (1d), forming recombination products C2H5NCO and/or C2H 5OCN, with pressure dependence: (1d) k1d = (0.090 ± 1.3) × 10-11 + (3.91 ± 0.27) × 10-10 P cm3 molecule-1 s-1. The radicals were generated by the 248 nm photolysis of ClNCO in an excess of C2H 6. Quantitative infrared time-resolved absorption spectrophotometry was used to follow the temporal dependence of the reactants and the appearance of the products. Five species were monitored, HCl, NCO, HCN, HNCO, and C 2H4, providing a detailed picture of the chemistry occurring in the system. Other rate constants were also measured: ClNCO + C 2H5, k10 = (2.3 ± 1.2) × 10 -13, NCO + C2H6, k2 = (1.6 ± 0.11) × 10-14, NCO + C4H10, k4 = (5.3 ± 0.51) × 10-13, with units cm3 molecule-1 s-1 and uncertainties of one-standard deviation in the scatter of the data. the Owner Societies.
- Glen Macdonald
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- Pyrolysis nozzles coupled to a microwave spectrometer with stark modulation for the detection of transients species in a supersonic expansion
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Two types of pyrolysis nozzles have been constructed and coupled to a new Stark modulated microwave spectrometer. The nozzles were tested on their ability to generate rotationally cooled transient species through a supersonic expansion. The transients species vinylamine, thioketene and ketene were generated and detected using nozzle temperatures ranging from 400-800°C. Pyrolysis temperatures were generally lower than those used in normal flow pyrolysis experiments and rotational temperatures of ca. 10 K were achieved. A preliminary investigation of the jet nozzle pyrolysis of 3-methyl-4-hydroxyiminoisoxaline-5-one was carried out and showed a different distribution of CHNO pyrolysis products to that observed in previous low pressure studies. by Oldenbourg Wissenschaftsverlag, Muenchen.
- McNaughton, Don,Evans, Corey J.
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p. 1313 - 1327
(2007/10/03)
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- Kinetics and mechanism of the thermal decomposition of azodicarbonamide, I
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The study on the kinetics of the thermal decomposition of azodicarbonamide, H2NCON = NCONH2 suggested a mechanism according to the scheme H2NCON=NCONH2->N2+2H2NCO', followed by the formation of a complex, H2NCON=NCONH2 + H2NCO->[H2NCON'-NHCONH2-NHCO] which decomposes rapidly to hydrazodicarbonamide (H2NCONH-NHCONH2) CO and N' or reacts with H2NCO' to form hydrazodicarbonamide and cyanic acid. This mechanism was confirmed by the computerized simulation of the measured kinetic curves of CO, N2, and cyanic acid, determined by gravimetric, volumetric, gas Chromatographie methods. Simulation of DSC curves confirmed also this mechanism by the fact that the sum of the reaction heats of the endo- and exothermic steps (calculated by the rate equations derived from the mechanism) resulted the measured reaction heat.
- Levai, Gyula,Nyitrai, Zs,Meszlenyi, Gabor
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p. 885 - 900
(2007/10/03)
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- Heterocumulenes, 9. Ethenedione oxime: Photochemical generation and matrix-spectroscopic identification
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The title compound 2, a very close derivative of the still elusive ethenedione (1), was generated by photocleavage of the three different precursor molecules 7-9 in an argon matrix at 10 K. The structure elucidation of monoxime 2 is based on the comparison of the experimental and calculated IR spectrum. VCH Verlagsgesellschaft mbH, 1996.
- Maier, Guenther,Reisenauer, Hans Peter,Roether, Bernd,Eckwert, Juergen
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p. 303 - 306
(2007/10/03)
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- XCN (X=Cl, Br and I): a novel source of isocyanogen
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Ambient light photolysis of gaseous BrCN, ClCN, and ICN results in the production of isocyanogen (NCNC) as the sole CN containing product. The flash vacuum pyrolysis of BrCN (1100°C and E-5 mbar) generates NCNC, NCCN, HOCN, HNCO and the CN radical.
- Blanch, Rodney J.,McCluskey, Adam
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p. 116 - 120
(2008/10/08)
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- Complex Oligooscillatory Behavior in the Reaction of Chlorite with Thiocyanate
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The reaction of chorite and thiocyanate has been studied in the pH range 1-4.The stoichiometry of the reaction is 2ClO2- + SCN- + H2O -> SO42- + 2Cl- + HOCN + H+.In excess ClO2-, ClO2(aq.) is formed as a product at the end of the reaction.ClO2 is formed from the reaction of excess ClO2- with HOCl: 2ClO2- + HOCl + H+ -> 2ClO2 + Cl- + H2O.At pH less then 4 and in excess SCN-, ClO2 is formed as an intermediate but is totally consumed at the end of the reaction.The reaction is very complex with oligooscillatory behavior in which ClO2 concentration goes through two maxima during the course of the reaction.The reaction is catalyzed by acid in pH range 2-4 but is retarded by acid in pH less than 2.The rate-determining step involves the reaction Cl(III) + SCN- + H+ -> HOSCN + HOCl.The acid retardation is due to the fact that ClO2- is more reactive than HClO2 and SCN- is a better nucleophile than isothiocyanic acid, HNCS.The reaction is autocatalytic in HOCl.The autocatalysis can be explained by using the asymmetric intermediate, Cl2O2, which produces two HOCl molecules after a two-electron reduction.The reaction of ClO2(aq) with SCN- was also studied, and it gives an autocatalytic rate of decay of ClO2.The mechanism involves initially forming ClO2- in an one-electron reduction followed by HOCl autocatalysis.Direct reaction between ClO2- and SCN- could be followed by using the FeSCN2+-SCN- reaction, which also showed acid retardation and HOCl autocatalysis.A 21-reaction mechanism was used to simulate the ClO2-SCN- reaction while a 24-reaction scheme was used to simulate the ClO2--SCN- reaction.There is resonable agreement between experiments and simulations in both cases.
- Chinake, Cordelia R.,Mambo, Elisabeth,Simoyi, Reuben H.
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p. 2908 - 2916
(2007/10/02)
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- Reaction between Hydrocyanic Acid and O(1D2) or O(3P) Oxygen Atoms in Low-Temperature Matrices
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The reactions of hydrocyanic acid with both excited and ground-state oxygen atoms have been examined in low-temperature matrices.The major products of HCN + O(1D2) reaction were isocyanic acid (HNCO) and cyanic acid (HOCN), confirming predictions of the intermediacy of HNCO and oxazirine on the pathway to the final products seen in the gas-phase reaction.In contrast, no evidence was found for reaction between HCN and O(3P) atoms in the matrix.
- Crowley, John N.,Sodeau, John R.
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p. 3100 - 3103
(2007/10/02)
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- Thermal decomposition of energetic materials. 30. Thermolysis of energetic metal-nitraminato complexes under conditions that simulate combustion
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The thermal decomposition of six energetic nitraminato complexes of Cu(II), Pd(II) and Ni(II) was investigated at 5°C/min by IR spectroscopy and DSC and at 100°C/s (to simulate combustion) by rapid-scan infrared spectroscopy. The objective was to correlate, insofar as possible, the structure and bonding of the parent complex to the decomposition behavior and products. The metal-nitraminato complexes decompose very rapidly. The gases liberated are farther along toward final combustion products than is the case with most organic nitramines subjected to the same thermal conditions. The thermolysis properties of M-(NH3)2[N(NO2)(CH2) 2N(NO2)] (M = Cu, Pd) complexes can be understood in terms of the relative strengths of the metal-nitrogen bond. Most of the NH3 is retained by the Pd complex in the condensed phase while decomposition occurs, whereas more of the NH3 is released to the gas phase in advance of decomposition by the Cu complex. There is circumstantial evidence that the high potential for forming ·H in the ammine complexes drives the thermolysis farther along toward the final, thermodynamically stable products. The Ni(II) complexes were more difficult to characterize because the thermal stimulus exploded the samples.
- Palopoli,Brill
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p. 2971 - 2976
(2008/10/08)
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- The Thermal Decomposition and Hydrolysis of Calcium Carbamoyl Phosphate
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Calcium carbamoyl phosphate (1) was prepared by adding an aqueous calcium chloride to a reaction solution of KH2PO4 with KOCN. 1 was unstable at room temperature. 1 was dehydrated to make anhydrous salt and thermally decomposed to liberate ammonia, cyanic acid, and carbon dioxide, finally resulting in the formation of calcium pyrophosphate in air.The aaparent activation energies for the three endothermic peaks of the DTA curve were estimated to be 50.0, 83.9, and 148.3 kJ/mol respectively.The hydrolysis of 1 in an aqueous solution apparently obeyed the first-order kinetics.The activation parameters for the hydrolysis of 1 were evaluated by using the 31P NMR spectra of 1 with the lapse of the reaction time.The activation energy was 92.2 kJ/mol; the activation enthalpy, 89.7 kJ/mol, and the activation entropy, -6.3 e.u.
- Shimasaki, Choichiro,Suzuki, Hiroki
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p. 379 - 384
(2007/10/02)
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- A NOVEL SYNTHESIS OF THE CYCLIC CARBINOLAMIDE MOIETY OF THE MAYTANSINOIDS
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The α-diketo-urethane 3 cyclizes to form the cyclic carbinolamide 4 using TMS triflate and 2,6-di-t-butylpyridine.The siloxy group of 4 is readily exchanged in methanol or water to form 6 or 7.Remarkably, 3 does not cyclize spontaneously or on standard acid catalysis.
- Petrakis, Konstantinos S.,Fried, Josef
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p. 3065 - 3066
(2007/10/02)
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