Wyniki wyszukiwania - BazTech

1

Sterical index: a novel, simple tool for the interpretation of organic reaction mechanisms

Dresler Ewa, Allnajar Radwan, Jasiński Radomir

Scientiae Radices

|

2023

|

Vol. 2, Iss. 1

69--74

EN

A new, simple index for the quantitative description of steric effects was proposed based on the results of DFT calculations. This effect was connected with the disturbance of synchronicity within transition states of the model Diels-Alder reaction. The obtained results offer the possibility of predicting steric effects determined by alkyl groups for a wide range of bimolecular processes.

2

The use of the steric effect of the carrier molecule in the polymer inclusion membranes for the separation of cobalt(II), nickel(II), copper(II), and zinc(II) ions

Radzyminska-Lenarcik E., Ulewicz M.

Polish Journal of Chemical Technology

|

2015

|

Vol. 17, nr 2

51--56

EN

In this study, palladium-modified nickel foam substrate was applied to examine ethanol oxidation reaction (EOR) in 0.1 The transport of cobalt(II), nickel(II), copper(II), and zinc(II) ions from chloride solutions across polymer inclusion membranes (PIMs), which 1-heptylimidazole (1̲) or 1-heptyl-2-methylimidazole (2̲) or 1-heptyl-4-methylimidazole (3̲) as the ion carrier was reported. The steric effect for carriers 2̲&enspand 3̲&enspdecreases the transport of all ions except Cu(II). The initial fluxes of metal ions transport across PIMs with the 1̲- 2̲&enspdecrease in the sequence: Cu(II) > Zn(II) > Co(II) > Ni(II), whereas for 3 they were Cu(II) > Zn(II) > Ni(II) > Co(II). The highest recovery values were obtained for Cu(II), this being 99 and 85% for carrier 1̲&enspand 2̲, respectively. In both membranes the degree of deposition of the Zn(II) ions was comparable. Zn(II), Co(II) and Cd(II) ions, which form complexes with coordination numbers 4 and 6, are more easily recovered with the use of carriers 2̲&enspand 3̲. Ni(II) ions, which form complexes with coordination number 6 only, practically remain in the feeding phase. PIMs with alkylimidazoles were characterized by non-contact atomic force microscopy.

3

Poszukiwanie różnic we właściwościach kompleksotwórczych alkiloimidazoli i ich wykorzystanie

Lenarcik B., Radzymińska-Lenarcik E.

Chemik

|

2011

|

Vol. 65, nr 4

237-242

PL

Wykazano, że zasadowość cząsteczek należących do poszczególnych szeregów homologicznych alkiloimidazoli zależy od po- łożenia podstawników alkilowych w pierścieniu i rośnie liniowo ze wzrostem ich długości. Zasadowość zmniejsza się w szeregu: 1,2,4-trialkiloimidazole > 1,2-dialkiloimidazole > 1,4- dialkiloimidazole > 2- alkiloimidazole > 1-alkiloimidazole. Zasadowość ligandów ma wielkie znaczenie w rozdzielaniu metali. Metodą podziału w układzie ciecz-ciecz wyznaczono stałe trwałości tworzących się w roztworach wodnych kompleksów 1-alkilo- oraz 1-alkilo-2-metyloimidazoli z Co(II), Ni(II), Cu(II) i Zn(II). Wykazano, że tworzenie się kompleksów z metalami przejściowymi zależy od dwóch efektów - sterycznego lub hydrofobowego danego liganda (alkiloimidazolu). Efekty te można wykorzystać do selektywnego rozdzielania Co(II) od Ni(II), Cu(II) od Co(II) i Ni(II), Zn(II), Cd(II), czy innych kationów, w zależności od wyjściowego składu mieszaniny wykonanej różnymi technikami separacyjnymi.

EN

It was shown that the alkalinity of the molecules belonging to different homologous series alkylimidazoles depends on the position of alkyl substituents in the ring and increases linearly with increasing length. Alkalinity decreases in the series: 1,2,4-trialkylimidazole> 1,2-dialkylimidazole > 1,4 – dialkylimidazole > 2 - alkylimidazole> 1-alkylimidazole. The alkalinity of the ligands is of great importance in the distribution of metals. The liquid-liquid partition method was used to determined the stability constants of Co(II), Ni(II), Cu(II), and Zn(II) complexes with 1-alkyl- and 1-alkyl-2-methylimidazoles in aqueous solutions. It was shown that the formation of complexes with transition metals depends on two effects – steric or hydrophobic of ligands (alkylimidazole). These effects can be used for the selective separation of Co(II) from Ni(II), Cu(II) from Co(II) and Ni(II), Zn(II), Cd(II) or other cations, depending on the initial mixture composition.

4

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

EN

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.