75-13-8Relevant articles and documents
Photochemistry of HNCO in Solid Xe: Channels of UV Photolysis and Creation of H2NCO Radicals
Pettersson, Mika,Khriachtchev, Leonid,Jolkkonen, Santtu,R?s?nen, Markku
, p. 9154 - 9162 (1999)
Photolysis of HNCO at wavelengths between 266 and 193 nm is studied in solid Xe with FTIR and laser-induced fluorescence methods. The channels HNCO → H + NCO (a) and HNCO → NH + CO (b) are operative in a Xe matrix. Channel b produces both isolated fragments and NH?CO complexes as characterized by the CO absorption. The MP2/6-311++G(3df,3pd) calculations are presented for the NH-CO complexes and compared with the experimental data. Photolysis of NCO produces mainly NO + C. A part of the carbon atoms form C2 after which C2- is created in a photoinduced charge transfer reaction. For comparison, in solid Kr, photolysis of HNCO produces additionally HOCN but this channel is absent in a Xe matrix. Upon annealing of the partially photolyzed matrix at 50 K, hydrogen atoms are mobilized and a radical H2NCO is formed by a reaction of a hydrogen atom with a HNCO molecule. Four IR absorptions of H2NCO are observed and they agree well with the MP2/6-311++G(3df,3pd) calculations. The assignment is supported by experiments with DNCO. The threshold for the photodecomposition of H2NCO is between 365 and 405 nm.
Reactivity of HNCO with NH3 at low temperature monitored by FTIR spectroscopy: Formation of NH4+OCN-
Raunier, Sebastien,Chiavassa, Thierry,Marinelli,Allouche,Aycard
, p. 594 - 600 (2003)
The reactivity of isocyanic acid (HNCO) with solid ammonia (NH3) was first studied at 10 K, using FTIR spectroscopy. The ammonium isocyanate (NH4+OCN-) is formed from a reaction between HNCO and NH3. Vibrational band assignments for NH4+OCN- have been given. On the other hand, when HNCO is adsorbed on amorphous NH3 film, the reaction does not occur. Warming up of this sample at 90 K induces the NH4+OCN- formation. Quantum calculations showed that the solvation of NH3 directly bonded to HNCO by at least three NH3 molecules plays a major role in the NH4+OCN- formation process and confirmed the spontaneous character of this reaction.
Paul, D. K.,Worley, S. D.,Hoffman, N. W.,Ash, D. H.,Gautney, J.
, p. 509 - 518 (1989)
Barnes, Clive E.,Brown, John M.,Fackerell, Alan D.,Sears, Trevor J.
, p. 485 - 496 (1982)
Simultaneous derivatization and trapping of volatile products from aqueous photolysis of thiamethoxam insecticide.
Schwartz,Sparrow,Heard,Thede
, p. 4671 - 4675 (2000)
An aqueous photolysis study was conducted with radiolabeled thiamethoxam, 4H-1,3,5-oxadiazin-2-imine, 3-[(2-chloro-5-thiazolyl)methyl]tetrahydro-5-methyl-N-nitro, to establish the relevance of aqueous photolysis as a transformation process for (14)C-[thiazolyl]-thiamethoxam. (14)C-[thiazolyl]-thiamethoxam was applied to sterile sodium acetate pH 5 buffer solution at a dose rate of approximately 10 ppm. The resulting samples were incubated for up to 30 days at 25 degrees C under irradiated and nonirradiated conditions. The irradiated samples were exposed to a 12-hour-on and 12-hour-off light cycle. Volatile fractions accounted for up to an average of 56.76% of the total dose for the irradiated incubations and a mixture of carbonyl sulfide (COS) and isocyanic acid (CONH). Verification of these components was accomplished by trapping with cyclohexylamine and formation of the thiocarbamate and the isocyanic acid derivatives. A similar method of trapping thiocarbamate metabolites was reported (Chen and Casida, 1978) where filter paper saturated with isobutylamine in methanol was arranged to trap (14)COS and (14)CO(2) under a positive flow of O(2) at 25 degrees C. Mass spectroscopy of the derivatized components confirmed the presence of carbonyl sulfide as the cyclohexylamine thiocarbamate and of isocyanic acid as its cyclohexylamine derivative. Evidence from this study indicates that thiamethoxam degrades significantly under photolytic conditions.
The formation and hydrolysis of isocyanic acid during the reaction of NO, CO, and H2 mixtures on supported platinum, palladium, and rhodium
Cant,Chambers,Angove
, p. 11 - 22 (2001)
The extent to which isocyanic acid (HNCO) is formed during the reaction of NO/CO/H2 mixtures over silica-supported Pt, Rh, and Pd was studied with the subsequent hydrolysis of HNCO on oxide systems placed downstream. HNCO formation was a characteristic feature of the NO + CO + H2 reaction over silica-supported Pt, Rh, and Pd. Platinum produced the largest quantity in two stages, i.e., from H2 and then using NH3 being formed as a coproduct. With Pd, HNCO arose largely from NH3 alone because H2 was totally removed by reaction with NO at low temperature. Rhodium gave rise to the least HNCO. Formation was confined to a narrow temperature area due to the coincident consumption of H2 and NO, which precluded NH3 reaction with CO and NO. Hydrolysis of HNCO to NH3 and CO2 was appreciable on SiO2 alone and faster when a metal was present. Other oxide systems gave complete hydrolysis to the limit of the water present and total reaction with even small excesses of water. The possible presence of HNCO in vehicle exhaust was not an issue since the presence of a vast excess of steam and an active washcoat in three-way converters would ensure complete hydrolysis. However, the latter process might contribute to ammonia emissions at moderate temperatures under conditions where CO is still present.
Initial state resolved electronic spectroscopy of HNCO: Stimulated Raman preparation of initial states and laser induced fluorescence detection of photofragments
Brown, Steven S.,Berghout, H. Laine,Crim, F. Fleming
, p. 8985 - 8993 (1997)
Stimulated Raman excitation (SRE) efficiently prepares excited vibrational levels in the ground electronic state of isocyanic acid, HNCO. Photofragment yield spectroscopy measures the electronic absorption spectrum out of initially selected states by monitoring laser induced fluorescence (LIF) of either NCO (X 2II) or NH (a 1Δ) photofragments. Near threshold, the N-H bond fission is predissociative, and there is well-resolved rotational and vibrational structure in the NCO yield spectra that allows assignment of Ka, rotational quantum numbers to previously unidentified vibrational and rotational levels in the ν1 N-H stretch and ν3 N-C-O symmetric stretch fundamentals in the ground electronic state of HNCO. The widths of NCO yield resonances depend on the initial vibrational state, illustrating one way in which initial vibrational state selection influences dissociation dynamics. Initial excitation of unperturbed ν1 (N-H stretch) states leads to diffuse NCO yield spectra compared to excitation of mixed vibrational levels. The higher energy dissociation channel that produces NH (a 1Δ) has coarser structure near its threshold, consistent with a more rapid dissociation, but the resonance widths still depend on the initially selected vibrational state.
Hikida, T.,Maruyama, Y.,Saito, Y.,Mori, Y.
, p. 63 - 72 (1988)
Unland
, p. 459 (1973)
Zobel,Pinnell
, p. 20,22 (1972)
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Spielman et al.
, p. 2520 (1950)
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Krakow, B.,Lord, R. C.,Neely, G. O.
, p. 148 - 176 (1968)
Photofragment imaging of HNCO decomposition: Angular anisotropy and correlated distributions
Sanov,Droz-Georget,Zyrianov,Reisler
, p. 7013 - 7022 (1996)
Photodissociation of jet-cooled isocyanic acid has been examined by photofragment ion imaging of H(D) from H(D)NCO and CO from HNCO, and by laser induced fluorescence (LIF) of NH(a 1Δ) from HNCO. Only modest recoil anisotropy is observed in the H+NCO channel at 243.1 nm (β=-0.13±0.05), while the D+NCO channel at approximately the same wavelength reveals no anisotropy (β=0.00±0.05), confirming that the dissociation of H(D)NCO from the opening of the H(D) channel proceeds via vibrational predissociation on the S0(1A′) surface. In contrast, substantial anisotropy (β=-0.66±0.08) is observed in the NH(a 1Δ)+CO channel at 230.1 nm, but this value can correspond to dissociation on either S0 or S1. The photolysis region between 243 and 230 nm thus appears important in providing clues to the dissociation mechanism and the competition between different potential energy surfaces. At 217.6 nm, product state distributions exhibit clear dynamical biases. CO is produced in both v=0 and v=1, while NH(a 1Δ) distributions correlated with different rovibrational levels of CO, although different in shape, are always cold, consistent with the global NH distribution measured by LIF. The NH distributions indicate dissociation on S1(1A″), and can be described by Franck-Condon mapping of transition state wave functions in the HNC bending coordinate without additional torque, implying little anisotropy in the potential along that coordinate. On the other hand, a larger torque is manifest in the CO rotational distribution. Although at 217.6 nm the dissociation is likely to be dominated by decomposition on S1, competition with radiationless decay is still manifest. From analysis .of the CO photofragment velocity distribution at 230.1 nm, the NH(a 1Δ)+CO dissociation threshold is determined at 42 765 ±25 cm-1.
Competitive photodissociation channels in jet-cooled HNCO: Thermochemistry and near-threshold predissociation
Zyrianov,Droz-Georget,Sanov,Reisler
, p. 8111 - 8116 (1996)
The photoinitiated unimolecular decomposition of jet-cooled HNCO has been studied following S1(1A″)←S0(1A′) excitation near the thresholds of the spin-allowed dissociation channels: (1) H (2S)+NCO(X 2∏) and (2) NH(a 1Δ)+CO(X 1∑+), which are separated by 4470 cm-1. Photofragment yield spectra of NCO(X 2∏) and NH (a 1Δ) were obtained in selected regions in the 260-220 nm photolysis range. The NCO(X 2∏)yield rises abruptly at 38 380 cm-1 and the spectrum exhibits structures as narrow as 0.8 cm-1 near the threshold. The linewidths increase only slowly with photolysis energy. The jet-cooled absorption spectrum near the channel (1) threshold [D0(H+NCO)] was obtained using two-photon excitation via the S1 state, terminating in a fluorescent product. The absorption spectrum is similar to the NCO yield spectrum, and its intensity does not diminish noticeably above D0(H+NCO), indicating that dissociation near threshold is slow. The NCO product near threshold is cold, as is typical of a barrierless reaction. NH (a 1Δ) products appear first at 42 840 cm-1, but their yield is initially very small, as evidenced also by the insignificant decrease in the NCO yield in the threshold region of channel (2). The NH (a 1Δ) yield increases faster at higher photolysis energies and the linewidths increase as well. At the channel (2) threshold, the NH (a 1Δ) product is generated only in the lowest rotational level, J=2, and rotational excitation increases with photolysis energy. We propose that in the range 260-230 nm, HNCO (S1) undergoes radiationless decay terminating in S0/T1 followed by unimolecular reaction. Decompositions via channels (1) and (2) proceed without significant exit channel barriers. At wavelengths shorter than 230 nm, the participation of an additional, direct pathway cannot be ruled out. The jet-cooled photofragment yield spectra allow the determination, with good accuracy, of thermochemical values relevant to HNCO decomposition. The following heats of formation are recommended: ΔHf0(HNCO) = -27.8±0.4 kcal/mol, and ΔHf0(NCO)=30.3±0.4 kcal/mol. These results are in excellent agreement with recent determinations using different experimental techniques.
Ashby,Werner
, p. 184 (1965)
Aminohydroxymethylene (H2N-C¨-OH), the Simplest Aminooxycarbene
Bernhardt, Bastian,Ruth, Marcel,Reisenauer, Hans Peter,Schreiner, Peter R.
, p. 7023 - 7028 (2021/09/02)
We generated and isolated hitherto unreported aminohydroxymethylene (1, aminohydroxycarbene) in solid Ar via pyrolysis of oxalic acid monoamide (2). Astrochemically relevant carbene 1 is persistent under cryogenic conditions and only decomposes to HNCO +
Trapping of Br?nsted acids with a phosphorus-centered biradicaloid - synthesis of hydrogen pseudohalide addition products
Beer, Henrik,Bl?sing, Kevin,Bresien, Jonas,Chojetzki, Lukas,Schulz, Axel,Stoer, Philip,Villinger, Alexander
supporting information, p. 13655 - 13662 (2020/10/27)
The trapping of classical hydrogen pseudohalides (HX, X = pseudohalogen = CN, N3, NCO, NCS, and PCO) utilizing a phosphorus-centered cyclic biradicaloid, [P(μ-NTer)]2, is reported. These formal Br?nsted acids were generatedin situas gases and passed over the trapping reagent, the biradicaloid [P(μ-NTer)]2, leading to the formation of the addition product [HP(μ-NTer)2PX] (successful for X = CN, N3, and NCO). In addition to this direct addition reaction, a two-step procedure was also applied because we failed in isolating HPCO and HNCS addition products. This two-step process comprises the generation and isolation of the highly reactive [HP(μ-NTer)2PX]+cation as a [B(C6F5)4]?salt, followed by salt metathesis with salts such as [cat]X (cat = PPh4,n-Bu3NMe), which also gives the desired [HP(μ-NTer)2PX] product, with the exception of the reaction with the PCO?salt. In this case, proton migration was observed, finally affording the formation of a [3.1.1]-hetero-propellane-type cage compound, an OC(H)P isomer of a HPCO adduct. All discussed species were fully characterized.