Intermolecular acyl exchange in 1-acyloxypyridinium salts

Dynamic NMR has been used to study the intermolecular acyl exchange of the N-oxides of pyridine and of their 1-acyloxypyridinium salts in CH₂Cl₂ and CH₃CN solutions. It has been established that the reaction is based on a bimolecular nucleophilic substitution mechanism. The reaction rate is determined by the state of the reacting particles in solution, the nature of the medium, and by structural effects.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 227–231, March–April, 1988.     

Studies of reaction heats and structures of complexes formed between macro compounds and SbCl5 in CCl4

The heats of reactions between the acyclic and cyclic macro-compounds are determined. The values can be used as a measure of the donor abilities of the macro ligands. Formation of two types of complexes between the macro compounds and SbCl₅ is established. The acyclic macro-compounds form 1:1 complexes, whereas the macrocyclic compounds only 1:2 complexes.     

Calculation and interpretation of the ir spectra of a number of N-acetylpyridinium salts

Based on calculation of frequencies and modes of normal vibrations of salts of N-acyl-4-dimethylaminopyridinium with N-acyl groups of different structures (acetyl, methoxycarbonyl, dimethylcarbamoyl), an interpretation is given of the IR spectra of the corresponding N-acyloinic cations. It is shown that the differences recorded in the experimental spectra of the salts are due to interaction between skeletal deformational vibrations of the aromatic ring and the deformational vibrations of acyl groups and to the manifestation of the characteristic vibrations of proper acyl groups. The stretching and deformational vibrations of the 4-dimethylamino group are insensitive to the nature of the acyl fragment. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 26–28, January–February, 2000.     

Studies of Silicon Podand Solvents

Three types of silicon podands, Me₂Si(OR)₂, EtSi(OR)₃ and PhSi(OR)₃, where R is a polyoxaethylene chain with different numbers of oxygen atoms (two, three or four), were obtained and studied by ¹H, ¹³C and ²⁹Si NMR methods. NMR spectra of ¹H, ⁷Li, ¹³C, ²³Na and ²⁹Si nuclei were also used for the study of lithium, sodium and rubidium complexes with the silicon podands. Theoretical calculations were performed using the PM3 hamiltonian. The heats of reactions between the compounds obtained and SbCl₅ were determined.     

DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

DFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.      

Interpreting vibrational spectra of N-tosyl-(4-dimethylamino)-pyridinium salts

Journal of Applied Spectroscopy -     

Calculating the intensities of absorption bands of the IR spectrum for benzylidene methylamine and its deuteroanalogs

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