Nitration of tetraalkyl-substituted methylenediamine derivatives with nitronium tetrafluoborate and nitrogen pentoxide

Conclusions Nitronium tetrafluoborate and nitrogen pentoxide nitrate the tetraalkyl derivatives of methylenediamine to the corresponding secondary nitramines. In the case of nitronium tetrafluoborate a second reaction product is the dialkylmethyleneimmonium tetrafluoborate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.1, pp.225–226, January, 1976.     

Quick method for determination of equilibrium temperature of calcium carbonate dissociation

A quick method for determination of equilibrium temperature of high temperature reactions, which is inexpensive and suitable for small industrial laboratories, is reported. Reaction of high temperature dissociation of calcium carbonate is used as example for quick method application. The method is based on calorimetric measurement, Hess Law, and thermodynamic calculations. The calibrated calorimeter is used to determine enthalpy change for reactions CaCO₃(s)?+?HCl(l), Ca(s)?+?2HCl(l), and CaO(s)?+?2HCl(l). By application of Hess??s energy cycle, enthalpies of formation of calcium carbonate and calcium oxide were determined. Acquired results were used to calculate enthalpy change for carbonate dissociation reaction. Calculated enthalpy change value was used for free energy change in dependence of temperature and also for equilibrium constant in dependence of temperature calculation using equations derived from basic thermodynamic equations. Using this method, equilibrium temperature for calcium carbonate dissociation reaction is found to be equal to 1154.14?K, which confirms accuracy of the method.     

Adsorption and dissociation equilibrium of benzoic acid on the mercury electrode

Adsorption of benzoic acid at the mercury electrode was studied in a wide pH range. The adsorption isotherms of benzoic acid from electrocapillary and capacity measurements were calculated. From the dependence of capacitance and potential of zero charge on pH the pK_el of benzoic acid was determined.     

Electron transfer dissociation of amide nitrogen methylated polypeptide cations

Unmodified and amide nitrogen methylated peptide cations were reacted with azobenzene radical anions to study the utility of electron transfer dissociation (ETD) in analyzing N-methylated peptides. We show that methylation of the amide nitrogen has no deleterious effects on the ETD process. As a result, location of alkylation on amide nitrogens should be straightforward. Such a modification might be expected to affect the ETD process if hydrogen bonding involving the amide hydrogen is important for the ETD mechanism. The partitioning of the ion/ion reaction products into all of the various reaction channels was determined and compared for modified and unmodified peptide cations. While subtle differences in the relative abundances of the various ETD channels were observed, there is no strong evidence that hydrogen bonding involving the amide nitrogen plays an important role in the ETD process.     

Gas hydrate equilibrium dissociation conditions in porous media using two thermodynamic approaches

We employ two thermodynamic approaches, based on the equal fugacities and the equal activities, to predict the gas hydrate equilibrium dissociation conditions in the porous media. The predictions are made for the hydrate systems, CH₄/H₂O, C₂H₆/H₂O, C₃H₈/H₂O, CO₂/H₂O, CH₄/CO₂/H₂O, C₃H₈/CH₄/C₂H₆/H₂O, and CH₄/CH₃OH/H₂O. For the non-hydrate phase, we used the Trebble–Bishnoi equation in the fugacity approach and the Soave–Redlich–Kwong equation in the activity approach. For the hydrate phase, the van der Waals–Platteeuw model incorporated with the capillary model of Llamedo et al. [M. Llamedo, R. Anderson, B. Tohidi, Am. Mineral. 89 (2004) 1264–1270] was used in the two approaches. The predictions are found to be in satisfactory to good agreement with the experimental data. The predictive ability of the fugacity approach is better than that of the activity approach.     

Self-consistent fluid variational theory for the dissociation of dense nitrogen

The self-consistent fluid variational theory is used to calculate the pressure dissociation of dense nitrogen at high temperatures. The accurate high-pressure and high-temperature effective pair potentials are adopted to describe the intermolecular interactions, which are made to consider molecular dissociation. This paper focuses on a mixture of nitrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperature. The equation of state and dissociation degree are calculated from the free-energy functions in the range of temperature of 2000-15 000 K and density of 0.2-3.0 gcm(3), which can be compared with other approaches and experiments.     

Carbon–nitrogen bond dissociation energy values in C-nitrosocompounds

Measurements of the D(R? NO) bond strength in some C-nitrosocompounds have been made using an electron impact method. The appearance potential of the radical ion (R⁺) has been determined, the D(R? NO) bond energy being obtained from the relation The values obtained are: D(C₆H₅? NO) = 41 kcal/mole, D(t-C₄H₉? NO) = 34 kcal/mole, D(t-C₅H₁₁? NO) = 36 kcal/mole and D(i-C₃H₇? NO) = 36.5 kcal/mole. These values are in good agreement with the numerous estimations of Benson and coworkers and confirm that the C? N bond strength in C-nitrosocompounds is very much less than in nitrocompounds or in amines.     

The reaction ofα-H-Fluorocarboxylic acids with phosphorus pentoxide

Conclusions Depending on the reaction conditions, fluoroacids containing a hydrogen atom in the-position to the carboxy group react with phosphorus pentoxide to give either anhydrides or products of their further conversion.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1111–1114, June, 1966.     

Electrospun nano-vanadium pentoxide cathode

Nanocrystallites of vanadium pentoxide were synthesized by the hydrothermal treatment of electrospun composite nanofibers. Each crystallite of dimension ?100 nm was found to be a single crystal of δ-phase H_xV₄O₁₀ · nH₂O. The crystallinity and morphology was maintained on heating to 500 °C when V₂O₅ was formed. The electrochemical capacity of the nano-V₂O₅ in a lithium cell was found to be above 350 mAh/g. The columbic efficiency is close to 100% when small amounts of lithium bis(oxalato)borate is added to the LiPF₆ electrolyte.     

Dynamic equilibrium between dissociation and regeneration of the C-C bond in trispiro-conjoined cyclopropane compound

-The oxidation of 2,2-di(3,5-di-t-butyl-4-hydroxyphenyl)indan-1,3-dione by potassium hexacyanoferrate(III) afforded a trispiro-conjoined cyclopropane compound due to the bond formation between the ipso-carbons. Its cyclopropane ring was found to exist in solution in dynamic equilibrium with biradical species by the dissociation of the C-C bond, which is as long as 1.595 Å as revealed by X-ray crystal analysis.     

Spectrographic analysis of tantalum pentoxide

Summary The mutal influence of Fe, Si, Mo, Nb, Cr, Al, Ti, Ni on the spectrographic determination of these elements as trace impurities in tantalum pentoxide matrix has been investigated. In a preliminary experiment designed according to Plackett and Burman the influence of Fe and Al proved to be insignificant. Consequently both elements were excluded from further investigations. Based on experiments carried out on standard samples whose compositions resulted from factorial plans 2ⁿ, 3ⁿ, rotatable composite design and conventional calibration methods, the mathematical models of interference effects were fitted. In all the cases studied it was found that the correction of analytical results for the interference effects by means of polynomial models containing concentrations of interferents, was more effective than by means of conventional calibration methods. Those models in which a logarithmic analytical function was applied, proved to be most effective.

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Spektrographische Analyse von Tantalpentoxid Eine Untersuchung der Störeffekte

     

Study of nitrogen isotope-selective two-stage IR + UV dissociation of ammonia molecules

The one-photon IR excitation and subsequent UV dissociation of ammonia molecules selective with respect to nitrogen isotopes were studied. The selectivity of vibrational excitation is achieved by tuning CO₂ laser radiation to resonance with ¹⁴NH₃ or ¹⁵NH₃ molecules. The dependences of the yield of dissociation for each isotopic component and the selectivity on the buffer gas (N₂, O₂, Ar) pressure, the partial pressure of ammonia, and the time of delay between IR and UV laser pulses were established. At low pressures (67–270 Pa) of the isotopic mixture with a ¹⁵N concentration of 4.8%, the dissociation selectivity for ¹⁵N was 17. The mechanisms responsible for the selectivity of IR + UV-initiated dissociation are discussed. The phenomenological model has been developed that takes into consideration the effect of the interisotopic V-V exchange and V-T relaxation on the formation of the yield and selectivity of the two-stage IR+UV dissociation of ammonia.     

Kinetics of formation,dissociation and equilibrium constants of pentacyanoaquoruthenate(II) with heterocycles

The kinetics of formation and dissociation reactions of [Ru(CN)₅L]^3– with a series of heterocyclic ligands were studied in aqueous media. In this presence of an excess of heterocycle, the observed second order rate constants were calculated from the k_obs versus [ligand] plot at =0.100m NaClO₄. Activation parameters for the formation reactions (H=28±7kJmol^–1 and S=140±35JK^–1mol^–1) are comparable for all systems, indicating a common mechanism. The kinetics of exchange of coordinated heterocycles for 1,3,5-triazine yielded a rate saturation typical of a limiting dissociative mechanism. Activation parameters of the limiting first order specific rate of dissociation reactions were H=85±7kJmol^–1 and S=18±4JK^–1mol^–1. Equilibrium constants were calculated from the second order rates of formation and pseudo-first order rates of dissociation reaction.