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Wyszukujesz frazę "quaternary ammonium" wg kryterium: Temat


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Tytuł:
Cukrowe czwartorzędowe sole amoniowe
Sugar quaternary ammonium salts
Autorzy:
Dmochowska, B.
Sikora, K.
Samaszko-Fiertek, J.
Ślusarz, R.
Madaj, J.
Powiązania:
https://bibliotekanauki.pl/articles/172328.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
czwartorzędowe sole amoniowe
d-glikopiranozydy
celuloza
chitozan
quaternary ammonium salts
d-glicopyranosides
cellulose
chitosan
Opis:
Quaternary ammonium compounds (QACs) exhibit the properties of both inorganic and organic compounds, and their ionic nature gives them hydrophilic character. The popularity of these compounds is allied to their many applications and ease of synthesis. Most of QACs are stable up to 150°C, readily soluble in water, usually non-toxic in utilitarian concentrations, are surface active, and do not irritate the skin or have a noxious odour [1]. Many of them have fungicidal, bactericidal and algicidal properties [2–5]. The antiviral action of QACs, including against HIV [6, 7], has been reported. They are used as timber preservatives, disinfectants, fabric softeners, anti-electrostatic agents and antifriction substances [5, 8, 9]. In addition, certain drugs administered in cases of diabetes, cardiac arrhythmia, neuroses, allergies and even carcinomas are QACs. Finally, QACs are used in chemical synthesis as catalysts, in phase-boundary catalysis [11], in the reduction of aldehydes and alkenes, and in the Friedl-Crafts reaction. In literature there is only limited amount of information considering quaternary ammonium salts containing sugar substituents. Among them four group of compounds arises: salts linked to C6 atom in sugar, directly connected to anomeric carbon atom, linked trough hydrocarbon spacer and derivatives of polisacharides. Kirk at al. described the synthesis of biologically active QACs [15]. In the Menshutkin reaction between an iodo-derivative and trimethylamine (Scheme 4), these authors obtained compounds with bactericidal and fungicidal properties. The authors obtained a series of analogous compounds using carboxylic acids (with carbon chains of various lengths) ester linked to the C-6-OH group of a sugar derivative. Blizzard synthesized QAC derivatives of vancomycin [28]. It was noticed that the increased hydrophilicity of vancomycin following the addition to it of a suitable fragment enhanced its antibacterial properties [30, 31], one of the more active being a derivative containing an aminium group at position G-6 (Scheme 10). Examples of reactions, in which the terminal carbon atoms in methyl glucopyranosides and polysaccharides are functionalized, are the syntheses carried out by Engel et al. [33, 34], one of which is shown in Figure 5. These authors aimed to find compounds with antibacterial properties. In the first instance, the hydroxyl groups at atoms C-6 of the sugar units in cellulose were O-tosylated. Then, the terminal carbons were functionalized with tertiary amines, yielding QACs. The most effective bactericide among these compounds was the one with a 16-carbon chain, the structure of which is shown Figure 6.
Źródło:
Wiadomości Chemiczne; 2016, 70, 7-8; 497-518
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kataliza przeniesienia międzyfazowego jako nowoczesna technika w syntezie organicznej
Phase-transfer catalysis as a modern technique in organic synthesis
Autorzy:
Siewniak, Agnieszka
Chrobok, Anna
Powiązania:
https://bibliotekanauki.pl/articles/1853730.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
kataliza przeniesienia międzyfazowego
czwartorzędowe sole amoniowe
poli glikole etylenowe
katalizatory chiralne przeniesienia międzyfazowego
phase-transfer catalysis
quaternary ammonium salts
polyethylene glycols
chiral phase-transfer catalysts
Opis:
Phase-transfer catalysis (PTC) has been already known for 60 years and has an established position both on a laboratory and industrial scale. It is an energy-saving technique, ensuring high yields and selectivity under mild conditions. PTC is successfully used, among others, in the pharmaceutical, polymer, agrochemical industries, for the production of dyes, fragrances and flavors, to name a few. Currently, the development of phase-transfer catalysis is focused mainly on the search for active catalysts as well as extending the scope of its applications. In particular, catalysts immobilized on an insoluble carrier, which can be easily separated from the reaction mixture and recycled many times, are of great interest. The growing demand for chiral compounds has resulted in the development of phase-transfer catalysts which, while retaining the advantages of conventional PTC, will allow to obtain a product with high enantiomeric excess. This work characterizes the phase-transfer catalysis and presents examples of its applications in organic synthesis.
Źródło:
Wiadomości Chemiczne; 2021, 75, 9-10; 1297-1315
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
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