Infrared and raman spectra of crystalline nitric oxide

Infrared and Raman spectra of polycrystalline samples of nitric oxide N₂O₂, at temperatures between 18 and 80 K have been recorded, and several new low frequency peaks observed. The Raman spectrum of the liquid at 115 K has also been obtained, in an attempt to distinguish between vibrations characteristics of the dimerized molecule and of the lattice. The observed features are discussed in terms of the known molecular and crystal structures.     

Infrared intensities of some SiH-containing compounds in the gas-phase

Infrared intensities measured in the gas-phase are reported for CH3SiH3, CH3SiD3, (CH3)2SiH2, (CH3)2SiD2, (SiH3)2CH2, (SiD3)2CH2, Si2H6, SiH2Cl2 and (SiH3)2O. These are compared with theoretical estimates from HF, MP2 and B3LYP calculations with the 6-311G** basis set. Literature values of nuCH intensities per bond from 18 compounds correlate linearly with the values calculated at MP2 and B3LYP levels: the corresponding HF plot is slightly curved. The new HC(Si) data fit these correlations adequately. In similar plots for SiH stretching intensity, the point for SiH2Cl2 is displaced, especially at the HF level. The lack of relation of nuCH or nuSiH intensity to Mulliken atomic charge points to the effect of varying atomic charge flux in the parameter thetamu/thetar. Anomalies associated with nuSiH intensities influenced by chlorine or OR substitution and previously explained by d(pi)-p(pi) bonding are attributed instead to charge flux variation. For silyl groups, deformation band intensities are roughly additive according to the number of such groups. However, this is not the case for the methyl symmetric deformation bands in methyl and dimethyl silanes.     

Spectroscopic observation of nitrous oxide pentamers

Two new infrared bands in the ν(1) fundamental region of N(2)O are observed in a supersonic jet expansion and assigned to nitrous oxide pentamers. Each band is measured using both (14)N(2)(16)O and (15)N(2)(16)O. Although they are similar in appearance, the bands have slightly different lower state rotational parameters, and are thus assigned to distinct structural isomers of the pentamer. Cluster calculations using two N(2)O intermolecular potentials give results in good agreement with the observed spectra, and indicate that the two isomers probably have the same basic structure (which is unsymmetrical), but differ in the alignment (N-N-O or O-N-N) of one or two of the constituent monomers. Calculations using a resonant dipole interaction model also support the proposed assignment and structure. These are the first reported high-resolution spectra for N(2)O pentamers.     

Infrared intensities of lattice vibrations in molecular crystals

From the dynamic multipoles model an expression is derived for the dipole moment derivative governing the intensity of infrared absorption by lattice modes in molecular crystals. The result depends on non-local susceptibilities which take proper account of the local electric field in a way consistent with dielectric theory. It is shown that the non-local rsponse follows naturally from microscopic lattice dynamical theory. It arises from dipolar coupling and is intimately connected with the delocalized exciton states produced by the same mechanism. Intensities calculated for the iodine crystal are inproved by including the local field, but a point quadrupole field proves too anisotropic to yield the measured intensity ratio. The treatment shows that infrared intensities can be used to obtain unique effective molecular polarizabilities.     

Adsorption of nitrous oxide on the(6,0) magnesium oxide nanotube

Nitrous oxide adsorption on the pristine（6,0） magnesium oxide nanotube was studied by using density functional theory calculations.We present the nature of the N₂O interaction in selected sites of the nanotube.Adsorption energies corresponding to adsorption of the N₂O on the nanotube were calculated to be in the range -11.67 to -22.21 kJ mol^-1.Our results indicate that the N₂O molecule has a weak physical adsorption on the pristine models due to weak Van der Waals interaction between the nanotubes and N₂O molecule.The important results can be useful in production of the N₂O sensors.     

High-temperature carboxidation of cyclopentene with nitrous oxide

It is demonstrated by the example of cyclopentene that the noncatalytic oxidation of alkenes with nitrous oxide to carbonyl compounds (carboxidation), which is known to occur in the liquid phase at 150–250°C, can also take place in the gas phase at higher temperatures (300–475°C). Like liquid-phase carboxidation, the gas-phase reaction likely proceeds via a dipolar 1,3-addition mechanism. However, 4-pentenal is formed along with cyclopentanone in the gas phase. The 4-pentenal selectivity increases from 2.5 to 23% as the reaction temperature is raised. High-temperature cyclopentene carboxidation can be carried out in a paraffin melt (bp ～ 400°C). Filling the reactor with paraffin accelerates the reaction and reduces its activation energy.     

Microdetermination of nitrous oxide in gaseous mixtures

Zusammenfassung Eine kritische Untersuchung der Entwicklung der Mikrogasanalyse, beginnend mit den Arbeiten vonTimiriazeff undKrogh, führte zur Konstruktion einer Gasbürette, die die Vorteile früherer Modelle beibehält und gleichzeitig deren Nachteile zu vermeiden sucht. Außerdem mußten die spezifischen Schwierigkeiten bei der Analyse sehr kleiner Proben von Stickstoffoxydulmischungen wie sie in der Anästhesie vorkommen, berücksichtigt werden.Die gasvolumetrische Messung in engen Kapillaren hat den Nachteil, daß aus den Absorptionspipetten mitgeführte Verunreinigungen einerseits den verfügbaren freien Raum in der Kapillare verkleinern und anderseits die Oberflächenspannung an den Menisken derart beeinflussen können, daß die genaue Einstellung des Druckes in der gemessenen Gassäule in Frage gestellt wird. Aus diesem Grunde wird in der neuen Bürette das Gas für die Volumsbestimmung in eine verhältnismäßig weite Kapillare gebracht, die nur dort verengt wird, wo sich der Meniskus zur Zeit der Messung befindet. Die Messung erfolgt mit Hilfe eines Stempels, dessen Verschiebung mikrometrisch gemessen werden kann. Die Mikrometerstellung wird abgelesen, wenn die beiden Menisken der Gasblase eine Ringmarke im verengten Teil der Kapillare passieren. Aus der Differenz der Ablesungen und dem Durchmesser des Stempels ergibt sich das Volumen der Gasblase. Zur genauen automatischen Korrektur von während der Verdrängung der Gasblase durch den Stempel auftretenden Druck- und Temperaturschwankungen wird das Thermobarometer-Prinzip vonZuntz undHempel benutzt, wobei dafür gesorgt ist, daß die Menisken der abgesperrten Luftprobe und der Gasblase nur durch eine kurze und verhältnismäßig massive Quecksilbersäule getrennt sind. Bei kleinen Gasblasen kann man eine absolute Genauigkeit der Volumsbestimmung von ± 0,05 erreichen. Die Präzision der Bestimmung des Volumens großer Gasblasen (etwa 200) läßt sich jedoch nicht über einen Teil in zweitausend Teilen hinaus steigern.Die Spitze der Bürette endet in einer kleinen Quecksilberwanne, in der sich auch die Reagenzgläser befinden, die als Absorptionspipetten und Gassammelgefäße dienen. Die Arbeitsweise vonSeevers undStormont, die vonTreadwell an leicht zugänglicher Stelle beschrieben wurde, wird beim Überführen der Gasblasen von der Bürette in die Pipette und umgekehrt beibehalten.Die Konstruktion der Bürette und die Arbeitsweise mit derselben sind genau beschrieben. Beleganalysen sind in Tabellen angeführt.

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Résumé Une étude critique du développement de la microgazométrie depuis les travaux deTimiriazeff etKrogh, a conduit à la construction d'une burette à gaz, présentant les mêmes avantages que les modèles précédents, tout en réduisant les inconvénients.De plus, on devait envisager les difficultés spécifiques à l'analyse des échantillons très réduits d'oxyde azoteux en mélanges, comme ceux qui servent en anesthésie.La mesure gazométrique en capillaire étroit, présente l'inconvénient que les impuretés introduites dans les pipettes capillaires d'absorption réduisent le volume utilisable, et que d'autre part, la tension superficielle au niveau du ménisque peut en être influencée au point que l'établissement de la pression exacte dans la colonne gazeuse à mesurer soit sujet à caution.Dans la nouvelle burette, le gaz à mesurer, est introduit, pour cette raison dans un capillaire relativement large, retréci seulement là où l'on amène le ménisque au moment de la mesure.La mesure se fait à l'aide d'un plongeur, dont les déplacements sont appréciés micrométriquement.La lecture est faite, lorsque les deux ménisques de la bulle gazeuse passent dans la partie retrécie du capillaire en y dessinant chacun un cercle. De la différence des lectures et du diamètre du plongeur se déduit le volume de la bulle gazeuse.Les corrections précises de température et de pression sont rendues automatiques par l'emploi du thermobaromètre deZuntz etHempel, qui assure la séparation des ménisques des bulles d'air et de gaz au moyen d'une colonne de mercure relativement importante. La précision absolue dans la détermination de petits volumes gazeux atteint ± 0,05; celle dans la détermination des volumes plus grands (environ 200) ne descend pas au-dessous d'une partie pour 2000.La pointe de la burette aboutit dans un petit réservoir à mercure, dans lequel se trouve aussi un tube à réaction servant de pipette d'absorption et de réservoir à gaz.Le mode opératoire deSeevers etStormont, décrit parTreadwell, est maintenu par déplacement de la bulle gazeuse de la burette à la pipette et inversement.La construction de la burette et le mode opératoire sont décrits avec précision. Les analyses de références sont données en tableaux.

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With 7 figures.     

Interactions of nitrous oxide with fluorinated liquids

The interactions of nitrous oxide with fluorinated liquids are investigated by reporting original experimental results on gas solubility and interpreting them using molecular simulation. Nitrous oxide is highly soluble in the three fluorinated liquids studied-perfluorooctane, 1-bromoperfluorooctane (perfluorooctylbromide), and perfluorohexylethane-with mole fraction solubilities on the order of 0.03 under ambient conditions. An intermolecular potential model was developed for nitrous oxide, with a functional form of the Lennard-Jones plus point charges type, adjusted to the experimental multipole moments and to vapor-liquid equilibrium properties. The solubility of nitrous oxide in perfluorocarbon liquids was calculated by molecular simulation methods, and a dissimilar interaction parameter of 0.92 in the Lennard-Jones well-depths between solute and solvent had to be introduced to reach agreement with the experimental results, similar to what is found for hydrocarbon-fluorocarbon interactions. The structure of the solutions was studied by analysis of solute-solvent radial distribution functions, showing that, although electrostatic interactions are not predominant, a small orientational effect is still present between the dipole of nitrous oxide and those of the substituted fluorinated liquids.     

Decomposition of nitrous oxide on AlFe-PILC catalyst

Summary Two AlFe-PILC catalysts were prepared with different OH/metal ratio and applied in nitrous oxide (N₂O) decomposition reactions. The 100% conversion of N₂O with NH₃into N₂and H₂O was achieved below 500^oC with both applied catalysts. However, the activity of catalysts in direct conversion of N₂O into N₂and O₂did not exceed 40 % below 500^oC. In this reaction the activity of AlFe-PILC catalyst synthesized at higher OH/metal ratio (4) is higher compared to the activity of AlFe-PILC catalyst with OH/metal ratio (2). Free FeO·Fe₂O₃particles were registered in the AlFe-PILC catalyst with higher OH/metal ratio (4).     

Infrared spectroscopic and density functional theory studies on the reactions of yttrium and lanthanum atoms with nitrous oxide in excess argon

Reactions of laser-ablated Y and La atoms with N2O molecules in excess argon have been investigated using matrix-isolation infrared spectroscopy. Metal monoxide-dinitrogen complexes, OM(N2) (M = Y, La) and OYNN, have been formed during sample deposition and identified on the basis of isotopic shifts, mixed isotopic splitting patterns, and CCl4-doping experiments. The OYNN(+) and OLaNN(+) cation complexes appear during sample deposition and increase visibly upon broad-band irradiation (lambda > 250 nm) at the expense of the neutral metal monoxide-dinitrogen complexes. Density functional theory calculations have been performed on the products. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these species from the matrix infrared spectra. Furthermore, a plausible reaction mechanism for the formation of these products has been proposed.     

Infrared intensities: A new tool in chemistry.

The interpretation of the infrared intensities in terms of atomic polar tensors and of electrooptical parameters allows to derive rich information on the charge distribution in the molecules. Using the results of several studies of this kind, it is now possible to derive information on intramolecular and intermolecular interactions even from “poor” data such as absolute intensities of whole regions in the spectrum or even from relative intensities.     

Liquid-phase noncatalytic butene oxidation with nitrous oxide

The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N₂O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C₂—C₈ with nitrous oxide were analyzed using the previously published data. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 925–933, April, 2005.     

Interaction between nitrous oxide and ruthenium catalysts

TPD data indicate that N₂O is desorbed from Ru and -Al₂O₃ without decomposition in one step and from Ru/Al₂O₃ in two steps with simultaneous decomposition to nitrogen and oxygen.

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, N₂O Ru -Al₂O₃ , Ru/Al₂O₃— .

     

Radiolysis of nitrous oxide adsorbed on alumina ionic mechanism of radiolysis of nitrous oxide on alumina with small surface areas

A mechanism is proposed for the radiolysis of adsorbed N₂O describing the experimental dependences of the radiation-chemical yields of O _st ^– and N₂ on N₂O coverages.

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N₂O, - O _st ^– N₂ N₂O.

     

Infrared spectroscopic study on the thermal decomposition of external and internal gelation products of simulated mixed oxide nuclear fuel

The thermal decomposition of urania-ceria gel corresponding to the composition U(0.7)Ce(0.3)O(2+x) obtained through external and internal gelation routes were studied using infrared spectroscopy (IR). In the case of externally gelated compound, the gel decomposes with the release of H2O and NH3 below 500 degrees C. A part of the NH3 released is entrapped in the solid and above 500 degrees C self reduction occurs in which U(VI) in the gel is reduced to U3O8. The decomposition products were identified to be U3O8 and CeO2. In the case of internally gelated compound, decomposition similar to the one for externally gelated compound occurred below 500 degrees C. Above 500 degrees C the carbon present in the gel reduced U(VI) to UO2 which formed solid solution with CeO2 around 650 degrees C.     

Adsorption of nitrous oxide on metallic copper catalysts

With the help of UPS spectroscopy, it has been shown that N₂O decomposes into N₂ and surface Cu₂O over copper catalysts in the temperature range –150, –100°C. The surface oxide oxygen dissolved into the bulk above 100°C to some extent.

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, N₂O –150° –100°C, N₂ Cu₂O. 100°C.