Informacja

Drogi użytkowniku, aplikacja do prawidłowego działania wymaga obsługi JavaScript. Proszę włącz obsługę JavaScript w Twojej przeglądarce.

English (EN)·Polski (PL)·Yкраїнський (UK)
Przejdź do strony domowej biblioteki Centralna Biblioteka Wojskowa Link otwiera się w nowym oknie Logo biblioteki Prolib Integro - strona głównaCentralna Biblioteka Wojskowa

Wyszukujesz frazę "aromatyczność" wg kryterium: Temat

  Lista filtrów
Wyrównaj
    Wyświetlanie 1-3 z 3
    Tytuł:
    Historyczny rozwój koncepcji aromatyczności
    Historical evolution of the concept of aromaticity
    Autorzy:
    Ciesielski, A.
    Krygowski, T. M.
    Cyrański, M. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/172203.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    aromatyczność
    benzen
    węglowodory benzenoidowe
    delokalizacja elektronowa
    aromaticity
    benzene
    benzenoid hydrocarbons
    electron delocalization
    Opis:
    Aromaticity is one of the most important terms used in organic chemistry. It has been called as a “as a cornerstone of heterocyclic chemistry” or “a theoretical concept of immese practical importance”. The concept, in chemical sense, has been introduced by Friedrich August Kekulé von Stradonitz 150 ago. The paper presents the contribution to its development of many outstanding scientists: Emil Erlenmayer, Albert Ladenburg, Adolf von Baeyer, Victor Meyer, Heinrich Limpricht, Artur Hantzsch, Eugen Bamberger, Richard Willstätter, Ernest Crocker, James W. Armit, Robert Robinson, Erich Hückel, Artur Frost, Boris Musulin, Linus Pauling, Kathleen Lonsdale, Eric Clar, Haruo Hosoya, Henry Edward Armstrong, George W. Wheland, Fritz W. London, John Pople, Paul von Ragué Schleyer and others. Aromaticity is defined on the basis of four main criteria: energetic, geometric, magnetic and reactivity. Two modern definitions of the term are presented in chapter 2 (both are given in English).
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 9-10; 789-808
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Strukturalne konsekwencje wiązania wodorowego
    Strustural consequences of the h-bonding
    Autorzy:
    Krygowski, T.M.
    Szatyłowicz, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/171995.pdf
    Data publikacji:
    2011
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    wiązanie wodorowe
    podstawione fenole
    podstawione aniliny
    aromatyczność
    AIM
    NBO
    H-bond
    substituted phenols
    substituted anilines
    aromaticity
    atoms in molecules
    natural bond orbital
    NBO analysis
    Opis:
    Hydrogen bonding belongs to the most important chemical interactions in life and geochemical processes as well as in technologies, that is documented in many review articles [1-10], monographs [11-17] and numerous publications. Figure 1 presents how "popular" are studies concerning hydrogen bonds (the term H-bond/bonding/bonded in a title, key-words or in abstract) in the last decade. First information about H-bond formation appeared at the end of XIX and a few other at beginning of XX centuries [19-24]. Most common definition of H-bonding stems from Pauling [27], whereas the newest IUPAC definition was published very recently [26]. Most frequently H-bonding is experimentally described by geometry parameters [28, 32] - results of X-ray and neutron diffraction measurements, but NMR and IR/Raman spectroscopies are also in frequent use. Characteristic of interactions by H-bonding is usually discussed in terms of energies [29-31], with use of various quantum chemical theories [54-57] and applications of various models as AIM [35, 41, 42, 45-48] and NBO [43, 44] which allowed to formulate detailed criteria for H-bond characteristics [35, 48]. H-bonds are classified as strong, mostly covalent in nature [7, 29, 34], partly covalent of medium strength [35] and weak ones, usually non-covalent [7, 29, 34, 35]. Theoretical studies of H-bonding mainly concern equilibrium systems, however simulation of H-bonded complexes with controlled and gradually changing strength of interactions [61-71] are also performed. The latter is main source of data referring to effect of H-bonding on structural properties: changes in the region of interactions, short and long-distance consequences of H-bonding. Application of the model [61] based on approaching hydrofluoric acid to the basic center of a molecule and fluoride to the acidic one, (Schemes 2 and 3) allows to study changes in molecular structure of para-substituted derivatives of phenol and phenolate [62, 64] in function of dB…H, or other geometric parameter of H-bond strength (Fig. 2). It is also shown that CO bond lengths in these complexes is monotonically related to H-bond formation energy and deformation energy due to H-bond formation [65]. Alike studies carried out for para-substituted derivatives of aniline and its protonated and deprotonated forms [77, 78, 81] give similar picture (Fig. 3). AIM studies of anilines [77, 78] lead to an excellent dependence of logarithm of electron density in the bond critical point and geometric parameter of H-bond strength, dB…H presented in Figure 4. Substituents and H-bond formation affect dramatically geometry of amine group [66] in H-bonded complexes of aniline as shown by changes of pyramidalization of bonds in amine group (Fig. 5). Some short- and long-distance structural consequences of H-bonding are shown by means of changes in ipso angle (for amine group) in the ring and ipso-ortho CC bond lengths (Fig. 6). Moreover, the mutual interrelations are in line with the Bent-Walsh rule [84, 86]. Changes of the strength of H-bonds in complexes of p-substituted aniline and its protonated and deprotonated derivative are dramatically reflected by aromaticity of the ring66 estimated by use of HOMA index [87, 88] (Fig. 7), where strength of H-bonding is approximated by CN bond lengths. Scheme 4 presents application of the SESE [91] (Substituent Effect Stabilization Energy) for description in an energetic scale joint substituent and H-bond formation effects.
    Źródło:
    Wiadomości Chemiczne; 2011, 65, 11-12; 953-974
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    O zależnościach pomiędzy aromatycznością i efektem podstawnikowym w układach jednopierścieniowych
    On relation between substituent effect and aromaticity in monocyclic systems
    Autorzy:
    Szatyłowicz, Halina
    Krygowski, Tadeusz Marek
    Powiązania:
    https://bibliotekanauki.pl/articles/171709.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    aromatyczność
    HOMA
    NICS
    efekt podstawnikowy
    stałe Hammetta
    metody chemii kwantowej
    aromaticity
    harmonic oscillator model of aromaticity
    nucleus independent chemical shift
    substituent effect
    Hammett constants
    quantum chemistry modeling
    Opis:
    Aromaticity/aromatic and substituent/substituent effects belong to the most commonly used terms in organic chemistry and related fields. They are used for more than a century, and so far are the subject of thousands publications a year. The quantitative description of the aromaticity of planar π-electron cyclic molecules is based on four criteria: (i) they are more stable than their acyclic unsaturated analogues, (ii) bonds have intermediate lengths between those for the single and double ones, (iii) external magnetic field induces π-electron ring current, and (iv) aromatic systems prefer reactions in which the π-electron structure is preserved. conserved. Quantitative characteristics based on these criteria, named as aromaticity indices, allow to relate aromaticity to the substituent effect. This latter can be described using either traditional Hammett-type substituent constants or characteristics based on quantum-chemistry. For this purpose, the energies of properly designed homodesmotic reactions and electron density distribution are used. In the first case, a descriptor named SESE (substituent effect stabilization energy) is obtained, while in the second case – cSAR (charge of the substituent active region), which is the sum of the charge of the ipso carbon atom and the charge of the substituent. The application of these substituent effect descriptors to a set of π-electron systems, such as: benzene, quinones, cyclopenta- and cyclohepta-dienes, as well as some azoles, allowed to draw the following conclusions: (i) The less aromatic the system, the stronger the substituent influences the π-electron system. Highly aromatic systems are resistant to the substituent effect, in line with the organic chemistry experience that aromatic compounds dislike reactions leading to changes in the π-electron structure of the ring. (ii) Intramolecular charge transfer (resonance effect) is privileged in cases where the number of bonds between the electron-attracting and electron-donating atoms is even. These effects are much weaker when this number is odd. Classically, it may be related to traditional para vs meta substituent effects in benzene derivatives. We should note that in electron-accepting groups, such as CN or NO2 (and others), electron-accepting atoms are second counting from Cipso. (iii) In all cases, when the substituent changes number of π-electrons in the ring in the direction of 4N+2, its aromaticity increases, for example electron-donating substituents in exocyclic substituted pentafulvene, or a halogen atom in complexes with heptafulvene.
    Źródło:
    Wiadomości Chemiczne; 2019, 73, 3-4; 243-261
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

      Ta witryna wykorzystuje pliki cookies do przechowywania informacji na Twoim komputerze. Pliki cookies stosujemy w celu świadczenia usług na najwyższym poziomie, w tym w sposób dostosowany do indywidualnych potrzeb. Korzystanie z witryny bez zmiany ustawień dotyczących cookies oznacza, że będą one zamieszczane w Twoim komputerze. W każdym momencie możesz dokonać zmiany ustawień dotyczących cookies