Relationship of intensities of absorption bands of adsorbed molecules to the energy of adsorption and the number of adsorption sites

A derivation of an equation which makes it possible to relate the intensities of the absorption bands in the optical spectra of test molecules adsorbed on a surface to the number and energetics of the adsorption sites has been proposed. In the general case, the ratio between the intensities of absorption bands is determined by the energy of the interaction of the adsorbate with the surface sites, the ratio between the numbers of sites, and the oscillator strengths of the optical transitions of the adsorbed molecules. The validity of the equation has been confirmed by analyzing the transmission spectra of p-dimethylaminoazobenzene adsorbed on monosubstituted forms of Glukhov kaolinite containing singly (Na⁺, H⁺), doubly (Mg²⁺), and triply (A1³⁺) charged cations in its exchangeable positions.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 475–480, July–August, 1985.     

Rate and Equilibrium Constants of Dimethylcarbamoyl Transfer between Pyridine N-Oxides

Dimethylcarbamoyl transfer from N-acyloxypyridinium salts to pyridine N-oxides in acetonitrile occurs in one stage by the forced concerted S_N2 mechanism. The rate and equilibrium of the reaction are fairly described by the Brönsted equation. The Marcus equation provides a much higher quality of reactivity predictions.     

Acetyl Exchange between Pyridine N-Oxides in Acetonitrile Solutions: An Attempt to Apply the Marcus Equation to Acetyl Transfer

Forty-three (including eight identical) reactions of acetyl transfer from N-acetyloxypyridinium salts to pyridine N-oxides in acetonitrile solutions were studied. The rate constants k ₂ vary in the range 10⁷-10^{- 1} l mol^{- 1} s^{- 1}; the equilibrium constants K, in the range 10⁷-10^{- 7}; the activation enthalpy H , in the range 17-30 kJ mol^{- 1}; the activation entropy -S , in the range 60-85 J mol^{- 1} K^{- 1}; and the heat of reaction -H ⁰, within ±50 kJ mol^{- 1}. All reactions occur in a single stage by the concerted SN2 mechanism with a low degree of bond cleavage in the transition state. The rate and equilibrium of the acetyl exchange are satisfactorily described by the Brönsted equation. The quality of predicting the reactivity is substantially improved by introducing into the correlation equation a second parameter, the rates of identical reactions.     

Ground-based complex for checking the optical system

The purpose TUS space experiment is to study cosmic rays of ultrahigh energies produced by extensive air showers from space. The concentrator is located on satellite, made in the form of the Fresnel mirror towards the earth’s atmosphere, the focus of which is a photodetector. The angle of view of the mirror is ±4.5° that for a given height of the orbit corresponds to the area 80 × 80 km² on ground. The ground complex consisting of a number of stations, to check the optical system of the experiment is created, (their location and the amount will be determined after the launch of the satellite based on its actual orbit).     

Synthesis based on β-phenylethylamines X. Synthesis of new derivatives of phenylethylaminomethylbenzo-crown ethers

Three methods have been developed for the introduction of a β-phenylethylamine fragment into a benzo-crown ether molecule. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 796–800, November–December, 1998.     

Catalytic properties of V?Sb?O systems in acrolein oxidation

Catalytic properties of V-Sb-O systems in acrolein oxidation have been studied. It has been established that the changes in the activity and selectivity of the catalysts are due to the phase and chemical properties of the system.

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Method of Eliminating Systematic Errors of Atomic Absorption Analysis in Atomization of a Material in a Graphite Furnace

By taking as an example the obtaining of the spectra of the gas phase over alkali metal iodides and calcium fluoride, we show the possibility of eliminating systematic errors of atomic absorption analysis which are due to nonselective absorption of light. It is been suggested that it makes sense to create a database that would contain molecular absorption spectra of the most abundant substances and would be intended for use by chemistsanalysts.