化学法和气相色谱法联用测定含烯汽油中共轭二烯烃的含量

建立了用共轭二烯烃与马来酸酐Diels-Alder特性反应和非极性固定液SE-30填充柱(1m×1.7mmi.d.)气相色谱法联用分析含烯汽油中共轭二烯烃含量的方法。色谱分析一次只需4min;重复性好,油样分析4次的相对标准偏差为1.7％。同时,考察了碘和无水三氯化铝作Diels-Alder反应催化剂的能力及回流反应装置挥发损失的程度。在规定的化学反应条件下,碘与共轭二烯的物质的量比为6.2×10~(-4)时,无水三氯化铝与共轭二烯的物质的量比为1×10~(-3)～2×10~(-3)时,异戊二烯有最高的转化率,分别为68.5％和98.2％,装置的挥发损失率最大为0.38％。     

锗苯与甲醛和二苯甲酮的Diels-Alder反应的计算研究

采用密度泛函理论(DFT)在B3LYP/6-311G(d,p)水平对锗苯与甲醛和二苯甲酮的Diels-Alder反应的微观机理、势能剖面、取代基效应及溶剂化效应进行了理论计算。结果,所研究的反应均为协同的基元反应,形成Ge-O键的反应中,形成2个新键较大不同步,其它反应的不同步性相对较小。羰基碳原子上的苯基取代基于反应不利,而锗苯分子中锗原子上的C(CH_3)_3与CCl_3取代基则有利。在热力学和动力学上,有锗参与的反应均远比无锗的反应容易,而形成Ge-O键的反应比形成Ge-C键的反应容易,结果与实验一致。四氢呋喃溶剂对所研究反应的势能剖面影响较小。4个形成Ge-O键的反应在四氢呋喃溶剂中进行时,其活化能垒分别为38.03、89.75、29.92和29.87 kJ·mol~(-1)。     

Synthesis and properties of readily recyclable polymers from bisfuranic terminated poly(ethylene adipate) and multi-maleimide linkers

Polymers that can repeatedly polymerize and depolymerize at moderate conditions was designed and synthesized. Furyl-telechelic poly(ethylene adipate) [PEA2F] was prepared and copolymerized with bis- and tris-maleimides by Diels-Alder [DA] reaction at 60 °C. Though the reaction with bismaleimide proceeded partially to give a polymer whose molecular weight was only twice as large as PEA2F, the reaction with trismaleimide gave a product with a 3D-network structure. The latter product shows elasticity at room temperature. By keeping at 145 °C, these DA products were easily disconnected by retro-Diels-Alder [rDA] reaction to reproduce the starting macromonomer, PEA2F. The repetition of the cycle of the DA and rDA reactions induce the reduction of neither the mechanical properties of the DA products nor the molecular weight of the rDA products. Therefore, we have successfully obtained readily recyclable polymers.     

降冰片烯的合成研究进展

目前,降冰片烯合成方面的研究报道多为专利且年代跨度大,缺乏较为系统的综述。本文首先介绍了由（双）环戊二烯与乙烯合成降冰片烯的Diels-Alder反应机理,针对乙烯反应活性不足所采取的高压及高温两类补偿措施分别加以评述,并列举了其反应热及常见副反应等。结合高温高压及反应放热量大等特点,系统阐述了相关动力学研究方面的进展情况,为调控反应进程提供参考,以确保安全生产。本文还回顾了降冰片烯合成技术的发展过程,对比了现有液相工艺和气相工艺的优缺点,虽然气相工艺可以有效遏制副反应的发生,但由于气相工艺产量较低,目前实际生产中大多采用液相反应工艺,如何通过设计特殊结构的反应器以提高其混合效果是未来研究的关键所在。     

桐油制备3-正丁基-6-(1-癸烯酸基)-4-环己烯二酸

以桐油为原料制备3-正丁基-6-(1-癸烯酸基)-4-环己烯二酸,分子式为C22H34O6（C22三元羧酸）。首先通过酯交换反应得到桐油酸甲酯,桐油酸甲酯与马来酸酐经过Diels-Alder反应制备3-正丁基-6-(1-癸烯酸甲酯基)-4-环己烯二酸,再经过皂化、酸化和分离等过程得到C22三元羧酸。用FT-IR、MS及1H NMR对其结构进行表征。采用正交试验考察Diels-Alder反应的最佳反应条件为：桐油酸甲酯与马来酸酐投料比为1∶1.2,反应温度为160 ℃,反应时间为2 h。     

Identification of conjugated fatty acids by gas chromatography-mass spectrometry of 4-methyl-1,2,4-triazoline-3,5-dione adducts

4-Methyl-1,2,4-triazoline-3,5-dione was reacted with conjugated fatty acid methyl esters to form Diels-Alder cycloaddition products. The electron impact mass spectra of conjugated octadecadienoates and 9,11,13-octadecatrienoate were simple and informative and allowed the positions of the double bonds to be determined. The dienes gave single adducts whereas the triene formed four products that corresponded to two stereoisomers of the adducts of the 9,11-diene system and two of the 11,13-diene system. The method can be used to complement other methods for identifying conjugated fatty acids.     

A Sweet Galactose Transfer: Metabolic Oligosaccharide Engineering as a Tool To Study Glycans in Plasmodium Infection

The introduction of chemical reporter groups into glycan structures through metabolic oligosaccharide engineering (MOE) followed by bio-orthogonal ligation is an important tool to study glycosylation. We show the incorporation of synthetic galactose derivatives that bear terminal alkene groups in hepatic cells, with and without infection by Plasmodium berghei parasites, the causative agent of malaria. Additionally, we demonstrated the contribution of GLUT1 to the transport of these galactose derivatives, and observed a consistent increase in the uptake of these compounds going from naïve to P. berghei-infected cells. Finally, we used MOE to study the interplay between Plasmodium parasites and their mosquito hosts, to reveal a possible transfer of galactose building blocks from the latter to the former. This strategy has the potential to provide new insights into Plasmodium glycobiology as well as for the identification and characterization of key glycan structures for further vaccine development.     

Healing of carbon fiber reinforced plastics by Diels–Alder based polymers: Effects of healing agent concentration and curing cycle

Self-healing resin (Bismaleimide prepolymer, BMI pp) based on Diels–Alder reaction mechanism was integrated into high performance carbon fiber reinforced plastics (CFRPs). Reference and BMI pp modified CFRPs were manufactured by incorporating grains of the self-healing agent (SHA) in the mid-thickness interlaminar region through sieving. First, the effect of the SHA concentration on the toughening and healing performance of CFRPs was studied under mode I fracture loading. The SHA was able to enhance the interlaminar fracture toughness of the composite to a certain extent and also to offer a moderate thermally activated healing functionality. Also, the effect of the curing temperature on the same results was studied; it was found the decrease of the curing temperature slightly decreases the fracture toughness while increases the healing efficiency of the composite. Finally, optical microscopy examinations were conducted and three-point bending tests were utilized to study the in-plane mechanical properties of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47478.     

Note: Thermally removable epoxy adhesives incorporating thermally reversible diels-alder adducts

Thermally reversible adhesives are prepared through the reaction of aliphatic diamines and a diepoxy compound containing two Diels-Alder adducts. The diepoxy compound is formed via the Diels-Alder reaction between two epoxy-containing furans and a bismaleimide. The adhesive displays a T g of m 40°C and a constant shear modulus up to approximately 90°C. At temperatures exceeding 90°C the retro Diels-Alder reaction occurs, which leads to a significant loss in modulus. The loss of modulus is reversible with temperature. A thermally reversible adhesive is proposed based upon the loss of modulus at an elevated temperature, i.e., adhesives bonds are easily broken at elevated temperature where the modulus is low.