“…The 320 nm irradiation of 0.1 M [ 13 C 3 ]PA solutions for 2 h led to a mixture whose 13 C NMR spectrum (Figure C) reveals the presence of (1) carboxyl groups at δ = 170.4 and 180.1 ppm [vs 167.8 ppm in keto-PA and 174.9 ppm in 2,2-dihydroxypropionic acid (DHPA), the gem -diol of PA; Figure A], (2) carbonyl groups at δ = 204.2 and 217.4 ppm (vs 215.5 ppm for acetoin and 201.5 ppm for PA, panels B and A of Figure , respectively) that confirm the absence of acetoin, and (3) a group of ether signals in the range of δ = 78−84 ppm. The latter are in agreement with the resonances found in the products of the anionic polymerization of aqueous PA into linear polyethers. − The strong signal at 124.8 ppm in Figure C corresponds to the CO 2 product. 7 …”
The 320 nm-band photodecarboxylation of aqueous pyruvic acid (PA), a representative of the alpha-oxocarboxylic acids widely found in the atmospheric aerosol, yields 2,3-dimethyltartaric (A) and 2-(3-oxobutan-2-yloxy)-2-hydroxypropanoic (B) acids, rather than 3-hydroxy-2-oxobutanone as previously reported. A and B are identified by liquid chromatography with UV and ESI-MS detection, complemented by collisionally induced dissociation and 2H and 13C isotope labeling experiments. The multifunctional ether B gives rise to characteristic delta approximately 80 ppm 13C NMR resonances. Product quantum yields are proportional to [PA](a + [PA])(-1) in the range [PA] = 5-100 mM. CO2(g) release rates are halved, while A and B are suppressed by the addition of >1.5 mM TEMPO. A and B are only partially quenched in air-saturated solutions. These observations are shown to be consistent with an oligomerization process initiated by a bimolecular reaction between 3PA and PA producing ketyl, CH3C(OH)C(O)OH, and acetyl, CH3C(O)*, radicals, rather than by the unimolecular decomposition of 3PA into 1-hydroxyethylidene, 3HO(CH3)C: (+CO2), or [CH(3)C(O)* + *C(O)OH] pairs. A arises from the dimerization of ketyl radicals, while B ensues the facile decarboxylation of the C8beta-ketoacid formed by association of acetyl radicals with the ketyl radical adduct of PA. Since the radical precursors to A and B are scavenged by O2 with a low probability per encounter (k(sc) approximately 1 x 10(6) M(-1) s(-1)), PA is able to accrete into multifunctional polar species in aerated aqueous media under solar illumination.
“…The 320 nm irradiation of 0.1 M [ 13 C 3 ]PA solutions for 2 h led to a mixture whose 13 C NMR spectrum (Figure C) reveals the presence of (1) carboxyl groups at δ = 170.4 and 180.1 ppm [vs 167.8 ppm in keto-PA and 174.9 ppm in 2,2-dihydroxypropionic acid (DHPA), the gem -diol of PA; Figure A], (2) carbonyl groups at δ = 204.2 and 217.4 ppm (vs 215.5 ppm for acetoin and 201.5 ppm for PA, panels B and A of Figure , respectively) that confirm the absence of acetoin, and (3) a group of ether signals in the range of δ = 78−84 ppm. The latter are in agreement with the resonances found in the products of the anionic polymerization of aqueous PA into linear polyethers. − The strong signal at 124.8 ppm in Figure C corresponds to the CO 2 product. 7 …”
The 320 nm-band photodecarboxylation of aqueous pyruvic acid (PA), a representative of the alpha-oxocarboxylic acids widely found in the atmospheric aerosol, yields 2,3-dimethyltartaric (A) and 2-(3-oxobutan-2-yloxy)-2-hydroxypropanoic (B) acids, rather than 3-hydroxy-2-oxobutanone as previously reported. A and B are identified by liquid chromatography with UV and ESI-MS detection, complemented by collisionally induced dissociation and 2H and 13C isotope labeling experiments. The multifunctional ether B gives rise to characteristic delta approximately 80 ppm 13C NMR resonances. Product quantum yields are proportional to [PA](a + [PA])(-1) in the range [PA] = 5-100 mM. CO2(g) release rates are halved, while A and B are suppressed by the addition of >1.5 mM TEMPO. A and B are only partially quenched in air-saturated solutions. These observations are shown to be consistent with an oligomerization process initiated by a bimolecular reaction between 3PA and PA producing ketyl, CH3C(OH)C(O)OH, and acetyl, CH3C(O)*, radicals, rather than by the unimolecular decomposition of 3PA into 1-hydroxyethylidene, 3HO(CH3)C: (+CO2), or [CH(3)C(O)* + *C(O)OH] pairs. A arises from the dimerization of ketyl radicals, while B ensues the facile decarboxylation of the C8beta-ketoacid formed by association of acetyl radicals with the ketyl radical adduct of PA. Since the radical precursors to A and B are scavenged by O2 with a low probability per encounter (k(sc) approximately 1 x 10(6) M(-1) s(-1)), PA is able to accrete into multifunctional polar species in aerated aqueous media under solar illumination.
“…Termination of the polymerization reaction occurs via proton transfer from water or alcohol molecules. The anionic polymerization of α-carbonyl acids in water under high basic conditions has been reported by Kimura et al This type of polymerization reaction is rather unlikely under atmospheric conditions, which are typically acidic or neutral.…”
Section: Nonradical Reactionsmentioning
confidence: 83%
“…This is especially true for deliquescent particles, where polymer propagation is inhibited by the large number of different inorganic and organic compounds present in the ALW. There are three main types of polymerization: (i) anionic polymerization, (ii) cationic polymerization, and (iii) free radical polymerization …”
“…133 Moreover, this alpha-keto acid can be anionically polymerized to form the corresponding polyether ( Figure 35). 454 Very recently, Boamah et al employed pyruvic acid in a different manner. They prepared pyruvic acid modified low molecular weight chitosans as potential lead adsorbent materials.…”
Section: Lactic Acid Platform Based Polymersmentioning
The demand for petroleum dependent chemicals and materials has been increasing despite the dwindling of their fossil resources. As the dead-end of petroleum based industry has started to appear, today's modern society has to implement alternative energy and valuable chemical resources immediately. Owing to the importance of lignocellulosic biomass for being the most abundant and bio-renewable biomass on earth, this critical review provides insights into the potential of lignocellulosic biomass as an alternative platform to fossil resources. In this context, over 200 value-added compounds, which can be derived from lignocellulosic biomass by using various treatment methods, are presented with their references. Lignocellulosic biomass based polymers and their commercial importance are also reported mainly in the frame of these compounds. The review article aims to draw the map of lignocellulosic biomass derived chemicals and their synthetic polymers, and to reveal the scope of this map in today's modern chemical and polymer industry.
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