22400-26-6Relevant articles and documents
Photochemistry of HNCO in solid xenon: Photoinduced and thermally activated formation of HXeNCO
Pettersson, Mika,Khriachtchev, Leonid,Lundell, Jan,Jolkkonen, Santtu,Rasanen, Markku
, p. 3579 - 3583 (2000)
The preparation and characterization of a novel rare-gas-containing compound HXeNCO in solid Xe is described. HXeNCO is formed in two ways. Photolysis of HNCO at 193 nm in solid Xe directly produces HXeNCO providing the first experimental evidence of direct photoinduced formation of a HXY-type rare-gas compound (X = Xe, Kr; Y is an electronegative fragment), which can be attributed to relatively high photostability of HXeNCO. This finding particularly shows that the HXY compounds can be intermediates in the photolysis of HY in the presence of X. The amount of HXeNCO produced initially in photolysis of HNCO remains small because HXeNCO decomposes under irradiation. More efficient production of HXeNCO is achieved in the thermal reaction H+Xe+NCO→HXeNCO after photolysis of HNCO. HXeNCO has two strong IR absorptions: the asymmetric NCO stretch at 2148.3 cm-1 and the Xe-H stretch at 1788.1 cm-1. The assignment is supported by the deuteration experiments and the ab initio calculations. HXeNCO decomposes at 405 nm irradiation producing HNCO and (H+NCO).
Contrasting Photolytic and Thermal Decomposition of Phenyl Azidoformate: The Curtius Rearrangement Versus Intramolecular C-H Amination
Wan, Huabin,Xu, Jian,Liu, Qian,Li, Hongmin,Lu, Yan,Abe, Manabu,Zeng, Xiaoqing
, p. 8604 - 8613 (2017/11/24)
The decomposition of phenyl azidoformate, PhOC(O)N3, was studied by combining matrix isolation spectroscopy and quantum chemical calculations. Upon UV laser photolysis (193 and 266 nm), the azide isolated in cryogenic noble gas matrices (Ne and Ar, 2.8 K) decomposes into N2 and a novel oxycarbonylnitrene PhOC(O)N, which was identified by matrix-isolation IR spectroscopy (with 15N labeling) and EPR spectroscopy (|D/hc| = 1.620 cm-1 and |E/hc| = 0.024 cm-1). Subsequent visible-light irradiation (532 nm) causes rearrangement of the nitrene into phenoxy isocyanate PhONCO with complex secondary fragmentation (PhO· + ·NCO) and radical recombination species in matrices. The observation of PhONCO provides solid evidence for the Curtius rearrangement of phenyl azidoformate. In sharp contrast, flash vacuum pyrolysis (FVP) of PhOC(O)N3 at 550 K yields N2 and exclusively the intramolecular C-H amination product 3H-benzooxazol-2-one. FVP at higher temperature (700 K) leads to further dissociation into CO2, HNCO, and ring-contraction products. To account for the very different photolytic and thermal decomposition products, the underlying mechanisms for the Curtius rearrangement (concerted and stepwise) of PhOC(O)N3 and the intramolecular C-H amination of the nitrene in both singlet and triplet states are discussed with the aid of quantum chemical calculations using the B3LYP, CBS-QB3, and CASPT2 methods.
Quantification of the 248 nm photolysis products of HCNO (fulminic Acid)
Feng, Wenhui,Hershberger, John F.
, p. 829 - 837 (2014/03/21)
IR diode laser spectroscopy was used to detect the products of HCNO (fulminic acid) photolysis at 248 nm. Five product channels are energetically possible at this photolysis wavelength: O + HCN, H + (NCO), CN + OH, CO + NH, and HNCO. In some experiments, isotopically labeled 18O2, 15N18O and C2D6 reagents were included into the photolysis mixture in order to suppress and/or isotopically label possible secondary reactions. HCN, OC18O, C18O, NCO, DCN, and NH molecules were detected upon laser photolysis of HCNO/reagents/buffer gas mixtures. Analysis of the yields of product molecules leads to the following photolysis quantum yields: 1a (O + HCN) = 0.39 ± 0.07, 1b (H + (NCO)) = 0.21 ± 0.04, 1c (CN + OH) = 0.16 ± 0.04, 1d (CN + NH(a1Δ)) = 0.19 0.03, and 1e (HNCO) = 0.05 ± 0.02, respectively. The uncertainties include both random errors (1σ) and consideration of major sources of systematic error. In conjunction with the photolysis experiment, the H + HCNO reaction was investigated. Experimental data demonstrate that this reaction is very slow and does not contribute significantly to the secondary chemistry.
Kinetics of the CCO + NO and CCO + NO2 reactions
Thweatt, W. David,Erickson, Mark A.,Hershberger, John F.
, p. 74 - 79 (2007/10/03)
The kinetics of the reaction of CCO radicals with NO and NO2 were studied using time-resolved infrared diode laser absorption spectroscopy. The rate constants were determined to be kCCO+NO = (5.36 ± 0.5) × 10-11 and k
Kinetics of the C2(a3IIu) radical reacting with selected molecules and atoms
Becker,Donner,Freitas Dinis,Geiger,Schmidt,Wiesen
, p. 503 - 517 (2007/10/03)
Rate coefficients for reactions of the C2 radical in its a3IIu electronic state with H, N and O atoms and with C3O2, C4F6, H2, NO, N2O, C2H2, C2H4, C3 H4 and C6H6 were determined. This work represents the first study of reactions of C2(a3IIu) radicals with the atoms investigated at room temperature and 4 Torr total pressure. The bimolecular rate constants obtained for the atom reactions were kc2+o = (9.8 ± 1.0) × 10-11- , kc2+N = (2.8 ±1.0) × 10-11 and kc2+N-14, in units of cm3 s-1. In addition, the reaction C2 + O was found to be independent of total pressure in the range 2-60 Torr. For the reaction C2(a3IIu) + ethene (C2H4) a temperature and pressure independent rate constant of (9.5 × 1.2) × 10-11 cm3 s-1 was obtained in the temperature range 298-1000 K at 100 Torr total pressure and in the pressure range 5-100 Torr at 298 K. The following rate constants were determined at room temperature and a total pressure of 4 Torr for the reactions of C2(a3IIu) radicals with benzene (C6H6), acetylene (C2H2) and allene (C3H4): kc2+C6H6 = (4.9 ± 0.1) ×10-10, kc2+C2H2 = (1.0 ± 0.1) ± 10-10 and kc2+C3H4 = (1.9 ± 0.3) ×10-10, in units of cm3 s-1. The reaction C2 + NO was investigated at room temperature and 100 Torr total pressure, a rate constant kc2+NO = (6.8 ± 0.3) × 10-11 cm3 s-1 was obtained. The reaction C2 + N2O was studied at 4 Torr total pressure in the temperature range 300-700 K for which a temperature independent rate constant kc2+N2O = (3.1 ± 0.4)X 10-14 cm3 s-1 was determined. by Oldenbourg Wissenschaftsverlag, Muenchen.
Product branching ratios of the NH2(X2B1) + NO2 reaction
Lindholm, Ned,Hershberger, John F.
, p. 4991 - 4995 (2007/10/03)
The reaction of NH2(X2B1) with NO2 was studied at 298 K using time-resolved infrared diode laser spectroscopy to detect N2O and NO products. The N2O + H2O channel was confirmed to be a rather minor contribution to the overall reaction, with a branching ratio of 0.24 ± 0.04. The branching ratio of the NO + H2NO channel was measured to be 0.76 ± 0.1.
Dynamics of the O(1D) + ClNCO Reaction
Singleton, Steven M.,Coombe, Robert D.
, p. 9865 - 9870 (2007/10/02)
The reaction of excited O(1D) atoms with ClNCO was studied by pulsed photolysis of O3/ClNCO mixtures with the 249-nm output of a KrF laser.The rate constant for O(1D) quenching by ClNCO was determined to be k = (1.3 -+/- 0.3) * 10-10 cm3 s-1.Investigation of the possible products of this reaction indicated that production of ClO + NCO is a major channel, with a branching fraction greater than 0.20.No evidence was found for the production of NCl in its X3Σ-, a1Δ, or b1Σ+ states.An upper limit for the branching fraction to NCl + CO2 is 0.005.
Photochemistry of ClNCO
Gilbert, J. V.,Coombe, R. D.
, p. 4082 - 4085 (2007/10/02)
The gas phase chemistry that occurs after the photolysis of ClNCO at 248 nm is characterized by the action of two excited intermediates, N(2D) and N2(A).Each of these reacts with ClNCO to generate NCO(A 2Σ+), and blue emission from the NCO(A 2Σ+ -> X 2Π) transition is observed.The time profile of the NCO emission consists of two distinct components, a fast component arising from the N(2D) + ClNCO reaction and a slow component arising from the N2(A) + ClNCO reaction.The N(2D) is an initial photofragment and the N2(A ) is generated in the N(2D) + ClNCO reaction.The value of the rate constant for N(2D) + ClNCO is determined to be 7.0 +/- 0.8 * 10-11 cm3 s-1.The rate constant measured from the decay of the NCO emission in a previous work (2.1 +/- 0.2 * 10-11 cm3 s-1 ) is assigned to the N2(A) + ClNCO reaction.
Photodissociation of chlorine isocyanate
Bell, D. D.,Coombe, R. D.
, p. 1317 - 1322 (2007/10/02)
Gaseous ClNCO exhibits a continuous ultraviolet absorption feature peaked near 250 nm.Photolysis of this compound at 249 nm produces bright blue emission identified as the A2Σ+ -> X2Π transition in NCO.The excited NCO arises from a collisional process in which N(2D) atoms, produced directly by the photodissociation, react with the parent ClNCO.The rate constant for this process is k = (2.1 +/- 0.2)*10-11 cm3 s-1. From production of N(2D) by the 249 nm photolysis, the heat of formation of gaseous ClNCO is inferred to be ΔHf(ClNCO) >= 52.9 kcal mol-1. ClNCO is metastable with respect to the ground electronic states of NCl and CO by 8.2 kcal mol-1.
Spin Trapping of Radicals Formed during the Decomposition of Aromatic Diazonium Salts by Ultrasound
Rehorek, Detlef,Janzen, Edward G.
, p. 935 - 940 (2007/10/02)
The decomposition of aromatic diazonium compounds ArN2(+)X(-) (Ar = phenyl, 2,5-diethoxy-4-(N-morpholino)phenyl; X =BF4, PF6, B(C6H5)4, SCN, OCN, N3; 1a, 1c-f, 2b-f) by ultrasonic waves has been studied by e.s.r..The spin trapping technique has been shown to be a suitable method for the detection of free radical intermediates.
