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161.
Biodegradable poly(lactic acid) is regarded as one of the most promising biopolymers with large market potential, but its applications are limited by the poor mechanical properties, since PLA is rigid and brittle. To enhance its mechanical, thermal and processability properties, at this study the authors use small molecules maleic acid (MA) and its propyl ester derivatives monopropyl maleate (MPM) and dipropyl maleate (DPM) as alternative plasticizers. The morphological, thermal, and mechanical properties of plasticized PLA were evaluated by DSC, FTIR, 1H NMR, DMA, PLOM and SEM into two controlled environment desiccators: SiO2 and water-saturated atmosphere. The results show that the increase in the substitution of MA increasing PLA plasticization ability, decreasing the PLA Tg from 48 °C to 5 °C and increasing percentage strain, while the presence of carboxyl groups from MA and MPM entails in water absorption to the bulk of the films which leads to a hydrolysis of MPM to MA. FTIR and 1H NMR confirmed these results and show that the hydrolysis and plasticizer evaporation occurs as a function of time. SEM images of fractured films analyzed after conditioned during a one-month present porous surface for PLA/MPM. In conclusion, maleate propyl esters have excellent PLA plasticizing properties and could improve the (using, market employment of this polymer. 相似文献
162.
Kai Wu Liang‐Liang Wu Cong‐Ying Zhou Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2020,59(37):16202-16208
A transition‐metal‐free C(sp2)?C(sp2) bond formation reaction by the cross‐coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi‐substituted triphenylenes and three bioactive natural products, honokiol, moracin M, and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2‐rearrangement through a stepwise mechanism. 相似文献
163.
We have developed a facile and efficient procedure for the synthesis of diarylphosphate esters and amides. Using Zn(acac)2 as the catalyst, the reaction of diarylphosphoryl azides with aliphatic alcohols and phenols through an unusual P?N bond cleavage provided a number of diarylphosphate esters in good yields (22 examples, up to 94%). Additionally, various diarylphosphate amides were obtained from the corresponding amines in excellent yields as well (8 examples, up to 96%). 相似文献
164.
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166.
Aye Ünlü Kerem Teral Zübeyde Uurlu Aydn Ali A. Dnmez Hasan Soliman Yusufolu hsan al 《Molecules (Basel, Switzerland)》2022,27(3)
Polygala species are frequently used worldwide in the treatment of various diseases, such as inflammatory and autoimmune disorders as well as metabolic and neurodegenerative diseases, due to the large number of secondary metabolites they contain. The present study was performed on Polygala inexpectata, which is a narrow endemic species for the flora of Turkey, and resulted in the isolation of nine known compounds, 6,3′-disinapoyl-sucrose (1), 6-O-sinapoyl,3′-O-trimethoxy-cinnamoyl-sucrose (tenuifoliside C) (2), 3′-O-(O-methyl-feruloyl)-sucrose (3), 3′-O-(sinapoyl)-sucrose (4), 3′-O-trimethoxy-cinnamoyl-sucrose (glomeratose) (5), 3′-O-feruloyl-sucrose (sibiricose A5) (6), sinapyl alcohol 4-O-glucoside (syringin or eleutheroside B) (7), liriodendrin (8), and 7,4′-di-O-methylquercetin-3-O-β-rutinoside (ombuin 3-O-rutinoside or ombuoside) (9). The structures of the compounds were determined by the spectroscopic methods including 1D-NMR (1H NMR, 13C NMR, DEPT-135), 2D-NMR (COSY, NOESY, HSQC, HMBC), and HRMS. The isolated compounds were shown in an in silico setting to be accommodated well within the inhibitor-binding pockets of myeloperoxidase and inducible nitric oxide synthase and anchored mainly through hydrogen-bonding interactions and π-effects. It is therefore plausible to suggest that the previously established anti-inflammatory properties of some Polygala-derived phytochemicals may be due, in part, to the modulation of pro-inflammatory enzyme activities. 相似文献
167.
Luiz Pereira Ramos Helena Maria Wilhelm 《Applied biochemistry and biotechnology》2005,123(1-3):807-819
In recent years, the concept of producing biodiesel from renewable lipid sources has regained international attention. In
Brazil, a national program was launched in 2002 to evaluate the technical, economic, and environmental competitiveness of
biodiesel in relation to the commercially available diesel oil. Several research projects were initiated nationwide to investigate
and/or optimize biodiesel production from renewable lipid sources and ethanol derived from sugarcane (ethyl esters). Once
implemented, this program will not only decrease our dependence on petroleum derivatives but also create new market opportunities
for agribusiness, opening new jobs in the countryside, improving the sustainability of our energy matrix, and helping the
Brazilian government to support important actions against poverty. This article discusses the efforts to develop the Brazilian
biodiesel program in the context of technical specifications as well as potential oilseed sources. 相似文献
168.
硅胶-氧化铝层析柱-气相色谱法测定沉积物中邻苯二甲酸酯类有机物 总被引:14,自引:0,他引:14
建立了硅胶-氧化铝层析柱净化分离,GC—MS、GC—FID定性定量分析沉积物样品邻苯二甲酸酯类有机污染物Phthalate esters(PAEs)的方法。比较了Florisil、硅胶、氧化铝和硅胶-氧化铝层析柱对PAEs分离特征;优化了硅胶-氧化铝层析柱净化分离PAEs的条件。方法线性范围0.05~500μg/g,回收率75.3%~113.6%,相对标准偏差2.74%~12.2%,检出限0.29~1.2ng/g。内标法定量,应用于珠江口沉积物样品中PAEs测定,获得满意的结果。 相似文献
169.
Th. Beyrich M. Schleuder G. Mietz H. Wulff M. Gruno 《Journal of Thermal Analysis and Calorimetry》1995,45(6):1479-1490
The 4-nitrobenzyl ester of acetylphenylhydroxyacetic acid differs in its melting behaviour from other nitrobenzyl esters of phenylhydroxyacetic or acetylphenylhydroxyacetic acids, the racemate having a higher melting point than the enantiomers. By means of thermal analysis, IR spectroscopy and X-ray diffractometry the ester can be shown to occur in two crystalline modifications. In the process of solidification of the molten mass, at first a modification of higher energy is formed, obviously being caused by an excess of one enantiomer, which is then exothermally rearranged in the lattice of the racemate. 相似文献
170.
液相色谱串联质谱法同时测定垃圾渗滤液中的邻苯二甲酸酯和烷基酚 总被引:4,自引:0,他引:4
利用反相液相色谱-电喷雾-串联质谱法同时分析了水体中的6种邻苯二甲酸酯(DMP、DEP、DBP、DEHP、DOP和DNP)以及OP、NP和BPA。用Waters XTerraTMMS C18色谱柱,乙腈和乙酸铵溶液作为梯度洗脱的流动相。结果表明,9种物质的分离效果良好,邻菲二甲酸酯采用亚离子模式检测,烷基酚采用负离子模式检测。通过多反应监测模式(MRM)对各目标物进行定量,检出限为0.1~1μg/L。该方法已用于北京某垃圾填埋场渗滤液中相关物质的检测,结果表明:原水中邻苯二甲酸酯和烷基酚的总浓度为218~291μg/L,其中主要是DEHP。垃圾渗滤液处理工艺对这些物质有明显的去除效果。 相似文献