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Proces samo-dysproporcjowania enancjomerów podczas chromatografii kolumnowej

Wzorek Alicja, Kwiatkowska Magdalena, Urbaniak Mariusz, Gawdzik Barbara

Wiadomości Chemiczne

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2023

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[Z] 77, 5-6

425--448

EN

The review is devoted to self-disproportionation of enantiomers (SDE) phenomenon which has been observed for many different classes of chiral organic compounds. The SDE phenomenon occurs when the fractionation of an enantioenriched sample due the application of a physicochemical process under achiral conditions results in the variation of the proportion of the enantiomers present across the fractions, though the overall composition in terms of the sample ee remains unchanged. The SDE process can be considered in terms of separating the excess enantiomer from the racemate. The basic terminology related to SDE was described. The formation of the SDE under chromatographic conditions is the result of an association process occurring in a solution of a chiral, non-racemic compound. Information on preferred interactions leading to homo-/heterochiral supramolecules can be provided by quantum chemical calculations, NMR spectroscopy and comparison of crystal structures of the racemic and enantiomeric crystals. Several examples of the chromatographic experiments with different classes of compounds were given in two purposes 1) to highlight the possibility of application SDE during column chromatography as the method for enantiopurification of the chiral, non-racemic compounds; 2) to demonstrate that a standard workup (chromatographic purification, evaporation) can alter the stereochemical outcome of asymmetric reactions.

2

Koloidy w życiu codziennym

Kurek Tomasz, Kuryśko Kacper

Analit

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2023

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Nr 13

6--11

PL

Koloidy, czyli układy złożone z małych cząsteczek rozproszonych w medium, są obecne w wielu aspektach naszego codziennego życia. Jednym z najczęstszych zastosowań koloidów jest żywność. Wiele produktów spożywczych, takich jak mleko, ser i lody, to koloidy. Obecność koloidów w tych produktach może wpływać na ich teksturę, konsystencję i smak. Ponadto są one również stosowane w produkcji wielu produktów kosmetycznych i środków higieny osobistej, w tym balsamów, szamponów i past do zębów. Koloidy mogą pomóc w stabilizacji tych produktów, zapobiegając ich rozdzieleniu i zapewniając jednorodność [1]. Koloidy odgrywają również istotną rolę w miejscach o których większość z nas nie zdaje sobie sprawy, a które mają znaczny wpływ na nasze życie. Na przykład aerozole, w tym dezodoranty czy też leki w postaci sprayu, są koloidami. Układy tego typu nie są jednak tylko sztucznym tworem człowieka. Występują one również naturalnie, w postaci mgły dymu lub chmur. Dzięki koloidom możemy potwierdzić istnienie atomów, a także cieszyć się pięknym błękitnym niebem [2]. Podsumowując, koloidy są wszechobecne w naszym codziennym życiu i mają szeroki zakres zastosowań. Ich obecność znacząco wpływa nie tylko na właściwości i działanie różnych produktów, ale również na cały otaczający nas świat.

EN

Colloids, which are complex systems of small molecules dispersed in a medium, are present in many aspects of our daily lives. One of the most common applications of colloids is in food. Many food products, such as milk, cheese and ice cream, are colloidal suspensions. The presence of colloids in these products can affect their texture, consistency and taste. In addition, they are also used in the production of many cosmetic and personal care products, including lotions, shampoos and toothpastes. Colloids can help stabilize these products, preventing separation and ensuring homogeneity. [1] Colloids also play an important role in areas that most of us are unaware of, but which have a significant impact on our lives. For example, aerosols, including deodorants or drug sprays, are colloids. However, systems of this type are not just an artificial creation of man. They also occur naturally, in the form of smoke mist or clouds. Thanks to colloids, we can confirm the existence of atoms, and enjoy the beautiful blue sky. [2] In summary, colloids are ubiquitous in our daily lives and have a wide range of applications. Their presence significantly affects not only the properties and performance of various products, but also the entire world around us.

3

Intermolecular interactions for two chosen anthracene derivatives

Kania Sylwester, Kuliński Janusz, Kościelniak-Mucha Barbara, Słoma Piotr, Wojciechowski Krzysztof

Scientific Bulletin. Physics / Lodz University of Technology

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2021

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Vol. 42

5--12

EN

The nature of intermolecular interactions for anthrone and anthraquinone differs due to the symmetry of substitution of the central benzene ring, i.e. anthrone substituted with only one keto group and anthraquinone substituted with two keto groups. In order to interpret the interactions among the molecules, the interaction energies between molecules in crystals were calculated using DFT B3LYP calculations. The results reveal the consistency between calculated “lattice energies” and theirs terms and thermodynamical properties as density, boiling point and melting point of examined compounds.

PL

Przeprowadzono obliczenia oddziaływań międzycząsteczkowych wykorzystując program CrystalExplorer17 z wykorzystaniem pakietu oprogramowania Gaussian09. Obliczenia DFT wykazały zgodność pomiędzy uzyskanymi wartościami energii „sieci krystalicznej” badanych związków i jej składowych z osobna a wybranymi do analizy doświadczanymi właściwościami termodynamicznymi jak gęstość materiału, temperatura wrzenia i temperatura topnienia badanych związków. Badania wykazały inny charakter oddziaływań zachodzących podczas procesu topnienia i podczas procesu wrzenia. Proces topnienia związany jest z całkowitą energią sieci. Temperatura wrzenia związana jest z zerwaniem odziaływań pomiędzy pojedynczymi cząsteczkami. Decydujące jest tu zerwanie oddziaływania dipolowego i dyspersyjnego.

4

Badania rozkładu gęstości elektronowej w kryształach, czyli jak zobaczyć szczegóły struktury elektronowej cząsteczek

Kubicki M.

Wiadomości Chemiczne

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2014

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[Z] 68, 5-6

403--427

EN

X-ray structural analysis might be regarded as a method of visualizing molecules as they appear in the crystals. The model, which is conventionally and universally used in this method, the Independent Atom Model (IAM) assumes that the electron density distribution, which scatters the X-rays is built of the spherically-symmetrical, neutral atoms. This model is responsible for the unprecedented success of X-ray structural analysis, which reflects in about one million crystal structures (i.e. the sets coordinates of the atoms constituting the molecules) deposited in the various databanks (cf. Fig. 1), and in the speed and accuracy which the method has reached. In principle, in few hours one can get the complete information about the crystal structure. But this success is accompanied by negligence of the scientific virtue hidden beyond the IAM. In fact, it was known from the very beginning of the X-ray diffraction studies by von Laue and Braggs, that some fine details of the electron density distribution should be available. The technological advance (four-circle diffractometers, powerful X-ray sources, fast computers etc.) caused that in 1960’s the time was ripe for the development of the experimental studies of details of electron density distribution in the crystals, beyond the IAM. The early experiments by Coppens and co-workers proved that this information – about the electron density transferred to the covalent bonds, lone pairs, even intermolecular interactions – can actually be obtained and analyzed (Fig. 2). The need for the model which could be used in the least-squares procedure led to the formulation of so-called pseudoatom models, including the most popular till now, Hansen-Coppens model (eq. 2) in which the aspherical part is described in terms of real spherical harmonics. In this paper, the basics of the electron density studies is described in some detail, including the step-by-step description of a typical procedure from the experiment to the final steps of refinement. An example of the analysis of the high-resolution structure of 1,2-dimethyl-4-nitro-5-morpholine-imidazole hydrate is used to show an application of this method in studying the intermolecular interactions, including weak C-H···O and C-H···N hydrogen bonds. It is shown that the multipolar model is able to deliver more informations than the promolecular model with spherically symmetrical electron distributions.

5

Photopolymerization kinetics and molecular interactions in methacrylate-imidazolium based ionic liquid systems

Andrzejewska E., Dembna A.

Polimery

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2014

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T. 59, nr 6

459--465

EN

Photopolymerization of poly(ethylene glycol) monomethacrylate (PEGMM) in two imidazolium based ionic liquids (ILs) differing with the anion size and H-bond accepting ability, i.e. 1-ethyl- -3-methylimidazolium tetrafluoroborate ([EMIm][BF4]) and 1-ethyl-3-methylimidazolium trifluoroacetate ([EMIm][ATF]) was investigated to find the effect of the IL anion on propagation kp and termination rate ktb coefficients (by DSC) as well as molecular interactions in the system (on the basis of viscosity and FT-IR measurements). Polymerizations in bulk and in tricresyl phosphate (TCP) served as references. Both monomer/IL systems show strong viscosity synergism and viscosity deviations are positive indicating that viscosity of associates between the monomer and the ILs is relatively higher than that of pure components. The increase in kp values observed in ILs is higher for polymerization in [EMIm][BF4], which shows stronger Coulomb cation-anion attractions and lower H-bond accepting ability of the anion. The influence of the ionic liquids on the termination rate coefficient results from the viscosity of the monomer-IL system, taking account of viscosity synergism. On the basis of changes of imidazolium ring CH groups vibrations and carbonyl stretching vibrations (both in PEGMM and IL anion) two possible configurations of monomer-IL interactions were proposed: between the monomer carbonyl and C(2)-H hydrogen of the imidazolium cation in the case of [EMIm][BF4] and a configuration in which the monomer carbonyl interacts with the imidazolium cation located on the top of the ring, in the case of [EMIm][ATF].

PL

Zbadano kinetykę fotopolimeryzacji (metodą DSC) monometakrylanu glikolu polietylenowego (PEGMM) w dwóch cieczach jonowych (ILs) różniących się wielkością anionu oraz jego zdolnością elektronoakceptorową tworzenia wiązań wodorowych (HBA), tj. w tetrafluoroboranie 1-etylo-3-metyloimidazoliowym ([EMIm][BF4]) i trifluorooctanie 1-etylo-3-metyloimidazoliowym ([EMIm][ATF]). Dla porównania przeprowadzono fotopolimeryzację w masie i w fosforanie trikrezylu (TCP). Obydwa układy PEGMM/IL wykazują silny synergizm lepkości — lepkość asocjatów pomiędzy monomerem i IL jest większa, niż związków wyjściowych (rys. 1). Określono wpływ IL na przebieg polimeryzacji. Wyznaczono współczynniki szybkości propagacji kp i terminacji ktb w funkcji stopnia przereagowania wiązań podwójnych (rys. 3). Obserwowany wzrost kp w IL jest większy w przypadku polimeryzacji w [EMIm][BF4], która cechuje się silniejszym oddziaływaniem kulombowskim kation-anion oraz słabszą HBA anionu. Wpływ IL na ktb jest zgodny z ich wpływem na lepkość układu (ktb ~ 1/h) przy uwzględnieniu synergizmu lepkości. Na podstawie położeń pasm odpowiadających drganiom grup CH pierścienia imidazoliowego oraz drgań rozciągających karbonylu (zarówno w monomerze, jak i w anionie IL, rys. 4 i 5) zaproponowano dwie możliwe konfiguracje oddziaływań pomiędzy monomerem a IL: pierwszą pomiędzy karbonylem monomeru a wodorem grupy C(2)-H pierścienia imidazoliowego (w przypadku [EMIm][BF4]) oraz drugą, w której karbonyl monomeru oddziałuje z kationem będąc usytuowany ponad płaszczyzną pierścienia.

6

Elektrooptyczny efekt Kerra w chemii

Prezhdo O., Olan K., Zubkowa W., Preżdo W.

Wiadomości Chemiczne

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2011

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[Z] 65, 1-2

1-31

EN

The electro-optical Kerr effect finds wide application in conformational analysis of molecules and molecular aggregates [1–5], particularly in cases where the standard X-ray and NMR techniques cannot be used. For instance, NMR allows to establish conformations of linear and cyclic unsaturated organic compounds. However, it is less effective in an analysis of molecular complexes, particularly of those that have several rotational symmetry axes. In such cases a combination of techniques based on molecular dipole moments, electro-optical Kerr effect, optical Kerr effect, IR spectroscopy, and Rayleigh scattering can be applied [6]. The foundations of conformational analysis of molecular complexes using several complementary physical approaches are developed in Ref. [7]. The electro-optical methods are particularly useful for an investigation of intramolecular interactions [8–18]. The strength, direction and other details of intramolecular interactions can be determined by analyzing the deviations of the experimental molar Kerr constant (mK) from its value calculated according to the tensor-additive scheme that operates with polarizability tensors of molecular cores and functional groups [19, 20]. For instance, using this approach it has been shown that weakening of conjugation in an electron donor-acceptor chain can lead to flattening of the molecular structure [21]. The Kerr constant is also very sensitive to intermolecular interactions [22–29]. In order to assess quantitatively an extent of the solvent effect on the mK values, both molecular and continuum models of solution structure have been used [30, 31]. The mK values are greatly affected by the mutual orientation of solvent and solute molecules, which interact by dispersive, inductive and dipole-dipole forces [32]. Hydrogen and donor-acceptor bonding have an even stronger influence on the mK values [33]. The equimolar mixtures approach developed in Ref. [34] allows to determine the molar Kerr constant (mK), dipole moment (m), equilibrium constant (K) and, ultimately, structure of a molecular complex based on measurements of the Kerr constant (B), dielectric permittivity (e), density (d) and refractive index (n) of a series of dilute solutions of the complex. Future trends in the development of the electro-optical methods in chemistry are discussed. Theories that relate the electric-optic proprieties of molecules with their reactivity are particularly important. Such theories should be able to predict the changes in the polarizabilities and dipole moments of bonds, molecules and molecular aggregates during the course of chemical reactions.

7

Effects of intermolecular interactions on the 1H, 13C and 14N NMR chemical shifts of N,N-Dimethylformamide dissolved in monosubstituted benzenes

Jackowski K., Makulski W., Trenkner-Olejniczak Z.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 1

81-89

EN

1 H,13 C and 14 N NMR chemical shifts have been used to monitor the dilution process of JV,7V-dimethylformamide (DMF) in monosubstituted benzenes. Both the proton and carbon chemical shifts of non-equivalent methyl groups in DMF are spectacularly influenced by ASIS (Aromatic Solvent Induced Shift) effects at the low concentration of a solute. On the other hand, the destruction of DMF liquid structure itself is better seen when the 13C chemical shift of a carbonyl carbon and the 14N shift are verified. A good correlation between the latter NMR chemical shifts has been found. It is shown on the basis of GIAO-CHF model calculations that the destruction of solute dipole-dipole dimers may be responsible for the increase of carbonyl carbon and nitrogen shielding constants of DMF in solvents.