Yu. L. Frolov

Synthesis and spectroscopic investigation of aryloxy- and arylthioalkenes, alkynes, and allenes

Conclusion1.A series of aryloxy and arylthio derivatives of ethylene, methylacetylene, and allene have been synthesized. Allenyl ethers of p-cresol, p-chloro, p-bromo, p-nitro, and 2,4,6-trichlorophenol have been prepared for the first time by acetylene-allene isomerization of the corresponding propargyl ethers.2.It has been shown that the S atom in the compounds studied behaves as an effective bridge for the π, p, π-conjugated system. On account of the lower ionization potential for the unshared electron pair on S compared with O, the polarizability of the conjugated system in the sulfides is increased significantly. The s-trans conformation is apparently preferred for the phenylvinyl and phenylallenyl ethers.

Energy degradation processes of the electron excitation of the phenothiazine molecule

Conclusions1.The quantum yields of the fluorescence and triplet states of phenothiazine depend but slightly on the properties of the solvent.2.The rate constants of the fluorescence and intercombination conversion from the S1 state were measured.3.The sum of the quantum yields of the fluorescence, intercombination conversion, and photoionization is smaller than one.

Triplet exciplexes in reactions of electronically excited chloranil with unsaturated heterocyclic compounds

Conclusions1.In the system indole+chloranil+dioxane the formation has been demonstrated of a. triplet exciplex with complete charge transfer and a hydrogen bond between the components.2.The presence of a hydrogen bond in the dissociative state results in a decrease in the yield of free ion-radicals.

Donor-acceptor complexes of vinyl aryl ethers with maleic anhydride

1. Nuclear magnetic resonance and infrared spectroscopies have been used to characterize the donor-acceptor complexes formed between vinyl aryl ethers and maleic anhydride; the values obtained for the equilibrium constant and the enthalpies and entropies of complexing suggest that there is a slight increase in the donor activity of the vinyl ether of phenol when a methyl group is introduced into its benzene ring. 2. Donor-acceptor interaction of the maleic anhydride with the vinyl aryl ethers leads to the formation ofπ complexes through weak charge transfer from the highest occupied orbital of the ether to the lowest vacant orbital of the anhydride. Quantum-chemical calculations and measurements of the chemical shifts on the13C and1H nuclei of the vinyl ethers under action from the MA indicate that the donor HOMO embraces the unshared electron pair of the oxygen and the π electrons of the double bond and the benzene ring.

IR spectral and dipole moment studies of the conformational isomerism of vinyl sulfides

1. Alterations in the conformations and the conformational ratios of the vinyl sulfides are reflected by changes in the absorption band intensities at 650–750 cm−1 (υC-S-C) and 850–900 cm−1 (νC-S-C) and the values of the dipole moments. 2. Increasing the branching in the substituent decreases the proportion of the vinyl sulfide in the cis rotamer form.

Molecular and crystal structure of 1-(trifluoroacetyl)-2-methylhydrazine

It was shown by x-ray diffraction analysis that 1-(trifluoroacetyl)-2-methyl-hydrazine molecules are combined in a crystal into centrosymmetric hexameric association complexes by a system of N-H...N and N-H...O hydrogen bonds.

Investigation of electronic structure of allenyl ethers by means of photoelectron and UV spectroscopy

A study of the photoelectron spectra of alkyl allenyl ethers has demonstrated their similarity to spectra of alkyl vinyl ethers, with the exception of a band in the 10.0–10.3 eV interval due to ionization of the π-orbital of the allenyl fragment Cα=Cγ. According to data obtained by photoelectron spectroscopy and MNDO quantum-chemical calculations, alkyl allenyl ethers with straightchain substituents exist primarily in the s-cis conformation. The stable conformation of allenyl tert-butyl ether is the s-trans form. The long-wave absorption bands in the UV spectra of alkyl allenyl ethers at 255–275 and 208–213 nm are assigned to electronic transitions of the π → п* and п* → π* types; these are quite insensitive to s-cis/s-trans isomerism.

Photoelectron and ultraviolet absorption spectra of allenyl vinyl ethers

The electronic structure of allenyl vinyl ethers (I) has been studied with the aid of photoelectron and UV spectroscopy, as well as MNDO and CNDO/S quantumchemical calculations. Divinyl ether has been selected as a model system for these molecules. The photoelectron spectra of I are similar to the spectrum of divinyl ether, with the exception of the band at 10.2–10.6 eV. The long-wavelength band in the UV spectra of I has been assigned to a transition localized in the allene group. The short-wavelength band of I corresponds to the π → π* transition observed in divinyl ether.

Specific effect of pentafluorophenyl fragment on electronic state of carbonyl group in ketones, amides, and hydrazides containing a pentafluorophenyl group

Conclusions1.The effect of the C6F5 group on the ΝC=0 frequency of C6F5COR compounds depends on the structural features of the R fragment; for ketones, amides, and hydrazides there is steric inhibition of resonance in the C6F5CO group and an increase in the role of the inductive effect from C6F5.2.In N-dimethylpentafluorobenzamide the decrease in resonance is compensated by p,π-conjugation in the CON group, and the inductive effect of the C6F5 ring appears to be weaker than in pentafluoroacetophenone.3.The presence of the second nitrogen atom and the change in relative orientation of the unshared electron pair when affected by substituents at N1 and N2 in pentafluorobenzahydrazide molecules leads to an increase in the torsion angle in C6F5-CO in comparison to N-dimethylpentafluorobenzamide, which increases the -I effect of C6F5 on ΝC=0 in pentafluorobenzhydrazides.

Rotational isomerism and calculation of the vibrational spectrum of methyl vinyl selenide

Summary1.Methyl vinyl selenide exists in the form of a mixture of rotational isomers.2.On the basis of a calculation of normal vibrations an assignment has been made of the absorption bands in the Raman and IR spectra of methyl vinyl selenide on the assumption that the planar cis-conformer is the most stable. The model of the force field used for the calculations gives satisfactory agreement with experiment.