Based on a strategy of ground-state destabilisation of the N—C bond,a general protocol for the esterification of amides with carbohydrates was reported.This protocol offers mild reaction conditions,excellent yields,and broad substrate compatibility,thereby demonstrating great potential for the synthesis of glycoconjugates.Additionally,this method provides an alternative approach for addressing the challenging task of esterifying sterically hindered secondary hydroxyl group of carbohydrates and paving the way for advancements in carbohydrate-based pharmaceuticals.
Glycerol monolaurate(GML)is a widely used industrial chemical with excellent emulsification and antibacterial effect.The direct esterification of glycerol with lauric acid is the main method to synthesize GML.In this work,the kinetic process of direct esterification was systematically studied using p-toluenesulfonic acid as catalyst.A complete kinetic model of consecutive esterification reaction has been established,and the kinetic equation of acid catalysis was deduced.The isomerization reactions of GML and glycerol dilaurate were investigated.It was found that the reaction was an equilibrium reaction and the reaction rate was faster than the esterification reaction.The kinetic equations of the consecutive esterification reaction were obtained by experiments as k_(1)=(276+92261Xcat)exp(-37720/RT)and k_(2)=(80+4413Xcat)exp(-32240/RT).The kinetic results are beneficial to the optimization of operating conditions and reactor design in GML production process.
The selective oxidative esterification of aldehydes with alcohols to the corresponding esters has been one of the hot spots in scientific research and industrial synthesis.However,the application of precious metal catalytic systems is limited by their complicated synthetic steps and high cost.Thus a highly efficient,green,recyclable selective synthesis method of esters catalyzed by polyoxovanadate(POV)-based molecu-lar catalysts has been developed in this paper.The results show that supramolecular interaction between POV and 1,3-dibenzylimidazolium bromide(Act_(2)Im)can efficiently convert alcohols and aldehydes to the corresponding esters in high yield under much milder conditions.Mechanistic insight is also provided based on the control experiments,single crystal X-ray diffraction and cyclic voltammetry studies.
As a natural organic polymer,xanthan gum(XG)can alleviate the plastic deformation of gel ink under strong stress and realize the reasonable regulation of the rheological properties of gel ink.However,as the double-helix structure connected by hydrogen bonds cannot resist the mechanical environment of strong stress,XG shows poor shear resistance.In this study,a polymer gel with interpenetrating polymer network structure was prepared by esterifying XG,taking polystyrene maleic anhydride(SMA)as the modifier.In addition to retaining the excellent rheological properties of XG,the generated polymer gel also exhibited high shear resistance.The optimal addition amount of the esterification reaction modifier was determined as mXG:mSMA=5:3 according to the gel ink standard.With this amount,the viscosity of the modified xanthan gum(SXG)gel increased to 1578.8 mPa·s and 100.7 mPa·s at shear rates of 4 s1 and 383 s1,respectively,and the shear resistance increased more than 2 times compared to the unmodified one.It is because of the ester bond formed by esterification that the reaction strengthens the interaction between molecular segments,enabling the new gel to resist to strong mechanical stress.The new polymer gel studied in this paper and the proposed mechanism of action provide new insights for the development of high-end gel ink and also provide theoretical support for the study of rheological properties of non-Newtonian fluids.
Xiaokun LiMingyi WangZilu LiuSong YangNa XuWei ZhaoGan LuoShoujun Liu
