The purpose of this review is to examine how the chemistry of epoxy resins, an almost century-old chemistry, is also involved in this movement.Epoxy resins are characterized by both the flexibility of implementation and the qualities of the polymers obtained. Polymerization, to be modern, must be "controlled", which usually means capable of producing macromolecules of well-defined structure. Recent advances in macromolecular chemistry have revolutionized the way we perceive the synthesis of polymers. The aim of this study is to provide a thorough understanding of the electron transfer pathways of a D/A/D -conjugated molecule for potential application in organic electrochromic devices. The electronic, optical, and magnetic properties and geometric structures of the 1e– and 2e– oxidized hexachloroantimonate salts are fully characterized by a combination of electrochemistry, x-ray crystallography, UV-vis-NIR, EPR, NMR spectroscopies, and density functional theory (DFT) calculations. More notably, the decomposition of the sulfide endcapped radical cation to a ketone endcapped, 2e– oxidized product under ambient air proved the instability of the 1e– oxidized state. This gives new insight into the concentration dependent reactivity of SbCl5 as a chemical oxidant. The latter is deter-mined to be a product of electrophilic chloronium ion (2e–) oxidation at a critical SbCl5 concentration (0.1 M or higher) in dichloromethane, via formation of a chloride adduct intermediate which we confirm by high-resolution mass spectrometry.
In contrast, chemical oxidation by antimony(V) chloride (SbCl5) led to the identification of four different oxidized species (a) the 1e– oxidized state and (b) its decomposition route to a two-electron (2e–) oxidized molecule with a ketone terminal group, (c) the 2e– oxidized state and (d) its generation by atom transfer oxidation via formation of a chloride-adduct. Specifically, electrochemical oxidation undergoes a sequential two-step, one-electron (1e–) oxidation with a 117 mV difference between consecutive half wave potentials. The electrochemical and chemical oxidations proceed by two distinct pathways. The oxidation pathways and products of a discrete, sulfide endcapped donor-acceptor-donor (D/A/D) molecule, namely propylenedioxythiophene-benzothiadiazole-propylenedioxythiophene, are investigated. By comparison, the compound 6-cyclohexyl-12-fluoro-5,6,7,12-tetrahydrodibenzo azastibocine (1d) is found to exhibit the highest catalytic activity, together with facile reusability in scale enlarged synthesis.
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The fluorinated organoantimony(III) derivatives were found to be more active than that of the chlorinated, brominated and iodinated analogues, owing to the use of Sb–F moiety as hydrogen bond acceptor. The results of systematic structure-activity relationship study demonstrated that the strength of N→Sb donor-acceptor interaction could be synergistically modulated by tuning the property of the nitrogen substituents and halogen atoms adjacent to the central antimony atom, and consequently resulted in distinct catalytic performance towards organic reactions such as Mannich, cross-condensation, cyclization-aromatization and epoxides aminolysis reaction.
#Antimony chloride series#
Studies using 13C NMR (in the case of complexes) and infrared spectroscopy (for Sb2O5) indicated the stability of the systems during the reaction process.Ī series of organoantimony(III) halide complexes with tetrahydrodibenzoazastibocine framework were synthesized and employed as water tolerant Lewis acid catalysts. The activation energies (Ea) for GLY conversion were estimated to be 23.9 and 14.6 kJ mol−1, in the absence and presence of catalyst, respectively, indicating a reduction of around 40% in the Ea with the use of SbCl5. The apparent rate constants (kap) were determined and the values corroborate the catalytic efficiency of SbCl5, especially when compared to the reaction without catalyst. The best result was obtained at 80 ☌ using 0.166 mmol of SbCl5, with total conversion attained after 15 min, and selectivity of 31, 47, and 22% for MA, DA, and TA, respectively, after 180 min. To the best of our knowledge, this is the first time that this class of catalysts is evaluated in GLY acetylation to produce monoacetin (MA), diacetin (DA), and triacetin (TA). In this study, antimony complexes (SbCl5 and SbCl3) were investigated as catalysts in glycerol (GLY) esterification with acetic acid (AA), compared to Sb2O3 and Sb2O5.
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