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Polimeryzacja anionowa inicjowana reagentami przenoszącymi elektrony

Grobelny Z., Stolarzewicz A., Szczepański M., Piekarnik B.

Wiadomości Chemiczne

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2008

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[Z] 62, 9-10

849-873

EN

This work describes the polymerization processes with electron-transfer reagents. Alkali metals, salts of aromatic hydrocarbons radical anions, and solutions of alkalides, i.e. salts containing alkali metal anions and complexed alkali metal cations, belong to such species [33-39]. The alkali metals transfer one electron to vinyl and diene monomers in the heterogeneous systems [54-73]. The radical anions are also able to transfer one electron [74, 77-82], however, in some cases they behave as nucleophiles [82-85] or bases [86]. These initiators are applied for the polymerization of vinyl and oxacyclic monomers in homogeneous systems. Both of them are named single-electron-transfer (SET) reagents. The alkalides are two-electron-transfer (TET) reagents. Among them potassium potassides K-, K+(18-crown-6) and K-, K+(15-crown-5)2 in tetrahydrofuran solution are mostly used for the polymerization of various monomers [53]. The initiation with these salts is usually a multistage process. An organopotassium compound is formed as the intermediate product which after the protonation by crown ether becomes the real initiator of the polymerization of vinyl monomers [92, 93, 97, 100]. The organometallic intermediate can be also protonated by the monomer or can decompose with the elimination in the systems containing oxiranes [107, 110-113] or lactones [127]. Potassium alkoxides or potassium salts of carboxylic acids, respectively, are the genuine initiators in this case. Crown ethers, known as the stable activators of chemical reactions, can participate in these processes as the reagents [107, 110, 116]. In the ring-opening reaction they form unsaturated potassium alkoxides which serve as the additional initiating agents [53, 97].

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Voltammetric study of the Reduction of Triptindanones in N,N-Dimethylformamide

Jaworski J., Kuck D.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 9

1597-1604

EN

The mechanism of electroreduction of 9-triptindanone (1), 9,10-triptindanedione (2), and 9,10,11-triptindanetrione (3) was studied by use of the cyclic voltammetric method. All carbonyl groups were reduced giving one, two, and three one-electron cathodic peaks for 1, 2, and 3, respectively and the corresponding oxidation peaks. The first electron transfer is reversible and the radical anions formed are stable. Additional small peaks for 2 and 3 were discussed in terms of an adsorption of reactants and intermediates and their reactions with the participation of supporting electrolyte cations as well as the residual water.

3

Radiation chemistry of solid thiosulfate: optical absorption spectra

Zagórski Z., Rafalski A.

Nukleonika

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2000

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Vol. 45, nr 1

109-113

EN

Solid sodium thiosulfate, anhydrous and hydrated (5 H2O), was irradiated with 10 MeV electrons in a pulsed, high-dose (30 kGy) rate regime. The resulting optical absorption was measured by diffuse reflection spectophotometry (DRS) (absorption band in anhydrous salt at 360 nm, in hydrated salt at 418 nm). Absorption decays occurred at t1/2 = 80 h (anhydrous) and t1/2 = 9 h (hydrated) at room temperature. The yellowish radical ion formed in irradiated anhydrous thiosulfate was identified as [źS2O3]-, and not [źS2O3]3-, as proposed in previous nonoptical (EPR) investigations. The absorption spectrum of [źS2O3]- in a solid matrix was similar to the transient spectrum ascribed to the same radical, obtained by pulse radiolysis in aqueous solution, and had a lifetime many orders of magnitude shorter. A similar radical anion, but in the complex with adjacent water molecules from the hydration moiety, was observed in hydrated thiosulfate (Na2S2O3ź5 H2O).

4

Wear behaviour and tribochemical reactions of low molecular alcohols under boundary lubrication of the steel-on-aluminium system.

Kajdas Cz., Obadi M.

Tribologia

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1999

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nr 3

273-287

EN

Tribochemistry of Alcohols is very complex and important from the practical piont of view. This paper relates to the research aiming at better understanding of the aliphatic alcohol tribochemistry.Using mostly the steel ball-on-alluminium disc friction system experiments were carried out to generate tribochemical reaction s on the aluminium discto analyse the formed deposits FTIR surface analysis was used.New adsorptionbandsmostly in the region of 1530-1550 cm-1 were found They are asssigned to the specific structure of organometallic compounds with -in many cases-include duble bonding in the reion of 1600-1650 cm-1.It was also found that the dissocitation constant (pKa)values of C1-C$alcohols control the steel ball wear for both steel-on-aluminium and steel-on-steelsystems.

PL

W niniejszym artykule przedstawiono wyniki badań, mających na celu zrozumienie tribochemii alkoholi alifatycznych. Eksperymenty, polegające na generowaniu reakcji tribochemicznych na powierzchni dysku aluminiowego, przeprowadzano głównie w układzie tarciowym stal-aluminium. Do analizy odłożonych depozytów zastosowano mikrospektrofotometrię FTIR. Stwierdzono obecność nowych pasm absorpcyjnych zwłaszcza w obszarze 1530-1550 cm-1.Są one przypisywane specyficznej strukturze związków organometalicznych które w wielu przypadkach posiadaja wiązanie podwójne 91600-1650cm-1) Stwierdzono również że wartośc stałej dysocjacji pKa) dla alkoholi C1-C4 wpływa na wielkość zużycia kulki stalowej zarówno w układzie tarciowym stal-aluminium jak również w układzie sta-stal.