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Substituent Effects in the ortho Position: Model Compounds with a Removed Reaction Centre

Böhm S., Exner O.

Polish Journal of Chemistry

2007

Vol. 81, nr 5-6

993-1006

2' -Substituted phenylpropynoic acids 1 and - in less details - 2' -substituted (E)-phenyliminoacetic acids 3 were investigated theoretically as model for theortho substitution, in which direct steric interaction is prevented by the extended side chain bearing the reaction centre. Energies of the acid molecules and of their deprotonated forms were calculated within the framework of the density functional theory at the level B3LYP/6- 311+G(d,p)//B3LYP/6-311+G(d,p). The substituent effects were evaluated in terms of isodesmic reactions, on the one hand for the acidity, on the other separately for the acid molecules or for the anions. Contrary to the expectation, the steric interaction of the substituent with the side chain is rather strong. The substituent effects represent a blend of polar and steric effects, and cannot serve for deriving any set of standard ortho substituent constants free of proximity effects as it was originally believed.

Mass Spectra of Thioamides Derived from Resorcinol and Its Methyl Ethers

Sośnicki J., Jagodziński T., Danikiewicz W., Olejnik M.

Polish Journal of Chemistry

2000

Vol. 74, nr 4

483-493

The electron ionization-induced fragmentation patterns of thioamides, derived from resorcinol and its methyl ethers, are studied. Fragmentation pathways depend both on the N-substuent group and the benzene ring substuents. Rationalization for this observation, proved by deuterium labelling, is given.

Fragmentation of 1-methyl-1,2,3,4-tetrahydroquinoline-2,3-dicarboxylic acid derivatives upon electron ionization

Danikiewicz W., Wojciechowski K.

Polish Journal of Chemistry

1998

Vol. 72, nr 3

554-563

The electron ionization-inducted fragmentation patterns of cis-3a,4,9,9a-tetrahydro-4-methyl-2-phenyl-1H-pyrrolo[3,4-b]quinoline-1,3(2H)-dione derivatives have been studied. It was found that fragmentation starts at N-phenylsuccinimide ring and its pattern depends on the type and position of the substituents at carbon atoms 5-8. Peaks, which can be assigned to the products of the retro Diels-Alder opening of the nitrogen atom containing tetrahydroquinoline ring, were observed.