V. I. Minkin

Dipole moments and azole structures (review)

Data on the dipole moments of azoles are correlated and systematized. The possibilities of the method of dipole moments in the solution of a number of problems of the chemistry of azole-containing systems — the electronic structures of azoles, intermolecular association, tautomeric and conformational equilibria, and reactivities — are demonstrated. The experimental values of the dipole moments of azoles are tabulated.

A study of pyrazoles

The reactivity of pyrazolo[2, 3-a]pyridine in electrophilic substitution reactions has been studied. It has been shown that electrophilic attack is directed to position 3 (equivalent to position 4 of the pyrazole nucleus). The position of entry of the substituents was shown by chemical methods and was confirmed by a study of PMR spectra.

Identification of derivatives of 2H-chromenes and their acyclic tautomeric forms in the gas phase by mass spectrometry

It was established that mass spectrometry makes it possible to identify in the gas phase molecular ions with both the 2H-chromene structure and their acyclic tautomers from the characteristic (M-OH)+ and (M-ArNH)+ fragment ions, respectively. The fragmentation scheme was confirmed by methods involving dissociation of ions activated by collision and deuterium labeling. Measurement of the ionization energies of the investigated compounds makes it possible to exclude the possibility of the existence in the gas phase of a tautomeric form with an o-quinoid structure.

Three-dimensional structure of 3-acylindoles

On the basis of a comparison of the experimental dipole moments with the calculated values, as well as data from the UV, IR, and PMR spectra, it is shown that 3-acylindoles exist in the form of equilibrium mixtures of the planar S-cis and S-trans conformers with preponderance of the latter.