- Nucleophilic Opening of the Oxirane Ring with Tetraalkylammonium Salt Anions in the Presence of Proton Donors
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Abstract: The behavior of tetraethylammonium salts in nucleophilic opening of the oxirane ring of epichlorohydrin (ECH) in the system ECH–proton donor–Et4N+ X–, where proton donor is benzoic acid or 4-nitrophenol and X = PhCOO or NO3, was studied by the kinetic and spectrophotometric methods. The order of the reaction in tetraethylammonium salt, benzoic acid, and 4-nitrophenol was estimated as first, zero, and less than zero, respectively. The mechanism of nucleophilic opening of the oxirane ring of ECH was elucidated on the basis of monitoring of the accumulation of 4-nitrophenoxide ion in the system ECH–4-nitrophenol–Et4NX upon variation of the initial concentrations of both tetraethylammonium salt and proton donor (4-nitrophenol) itself. The anion X of the initial tetraethylammonium salt was found to be irreversibly consumed as a result of its attack on the oxirane ring with participation of the proton donor, which led to generation of tetraethylammo-nium 4-nitrophenoxide, and the latter catalyzed the subsequent formation of the final product. An increase in the concentration of 4-nitrophenol was accompanied by reduction of both the rate of formation of 4-nitrophenoxide ion and the overall reaction rate, which corresponds to a mechanism involving nucleophilic attack of the anion X on the oxirane ring that is not activated by the proton donor.
- Bakhtin, S. G.,Bespalko, Yu. N.,Shved, E. N.,Sinelnikova, M. A.
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p. 524 - 531
(2021/06/02)
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- Synthesis of isosorbide-based polycarbonates via melt polycondensation catalyzed by quaternary ammonium ionic liquids
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A series of quaternary ammonium ionic liquids (ILs) were synthesized and employed as catalysts for the production of poly(isosorbide carbonate) (PIC) from diphenyl carbonate and isosorbide via a melt polycondensation process. The relationship between the anions of the ILs and the catalytic activities was investigated, and the readily-prepared IL tetraethylammonium imidazolate (TEAI) was found to exhibit the highest catalytic activity. After optimizing the reaction conditions, a PIC with a weight-average molecular weight (Mw) of 25600 g/mol was obtained, in conjunction with an isosorbide conversion of 92%. As a means of modifying the molecular flexibility and thermal properties of the PIC, poly(aliphatic diol-co-isosorbide carbonate)s (PAIC)s were successfully synthesized, again using TEAI, and polymers with Mw values ranging from 29000 to 112000 g/mol were obtained. 13C NMR analyses determined that the PAIC specimens had random microstructures, while differential scanning calorimetry demonstrated that each of the PAICs were amorphous and had glass transition temperatures ranging from 50 to 115 °C. Thermogravimetric analyses found Td-5% values ranging from 316 to 332 °C for these polymers. Based on these data, it is evident that the incorporation of linear or cyclohexane-based diol repeating units changed the thermal properties of the PIC.
- Sun, Wei,Xu, Fei,Cheng, Weiguo,Sun, Jian,Ning, Guoqing,Zhang, Suojiang
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p. 908 - 917
(2017/05/22)
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- CATHODIC ESTERIFICATION OF CARBOXYLIC ACIDS
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A cathodic method for the esterification of carboxylic acids under mild conditions was found.The esterification proceeded smoothly at room temperature by the reaction of alkylating with quaternary ammonium carboxylates formed in a cathode chamber.
- Awata, Takeshi,Baizer, Manuel M.,Nonaka, Tsutomu,Fuchigami, Toshio
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p. 371 - 374
(2007/10/02)
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