Density （ρ） and viscosity （η） measurements were carried out for 4-aminobutyric acid in 0.0041,0.0125 and 0.0207 mol·L-1 aqueous salbutamol sulphate at T=308.15,313.15 and 318.15K.The measured values of dens...Density （ρ） and viscosity （η） measurements were carried out for 4-aminobutyric acid in 0.0041,0.0125 and 0.0207 mol·L-1 aqueous salbutamol sulphate at T=308.15,313.15 and 318.15K.The measured values of density and viscosity were used to estimate some important parameters such as apparent molar volume Vφ,limiting apparent molar volume Vφ0,transfer volume △Vφ0,hydration number Hn,second derivative of infinite dilution of partial molar volume with temperature 2Vφ0/T2,viscosity B-coefficients,variation of B with temperature dB/dT,free energy of activation per mole of solvent △μ10＊ and solute △μ20＊,activation entropy △S20＊ and activation enthalpy △H20＊ of the amino acids.These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.展开更多
Over the full range of compositions, in the ternary-pseudo-binary mixtures of x[（1-y）C6H5CH=CH2＋ yCH3COOC2H5（or C6H6）]＋（1-x）[（1-y）NMP＋yCH3COOC2Hs（or C6H6）], the apparent molar volumes of each pseudo-pure ...Over the full range of compositions, in the ternary-pseudo-binary mixtures of x[（1-y）C6H5CH=CH2＋ yCH3COOC2H5（or C6H6）]＋（1-x）[（1-y）NMP＋yCH3COOC2Hs（or C6H6）], the apparent molar volumes of each pseudo-pure component at different y values were calculated from the density data at 298.15 K and atmospheric pressure. The results show that the four parameters cubic polynomial can correlate the apparent molar volume with the molar fraction well over the full molar fraction range. The limiting partial molar volumes and the molar volumes of each pseudo-pure component were evaluated with different methods. Based on the limiting partial molar volume and molar volume at a certain y value, a new universal coefficient termed as solvation coefficient γ was defined to describe quantitatively the solvation degree of pseudo-pure solute and the interactions of solute-solvent molecules from the macroscopical thermodynamics viewpoint. The results demonstrate the solvation coefficients decrease with the amount of the third component increasing for each pseudo-pure solute, irrespective of the pseudo-pure solvent. Then the solvation degrees of each pseudo-pure component, the specific interactions between the solute molecule and the solvent one were discussed in terms of the solvation coefficient.展开更多
阐述了传统动力学模型用以描述天然产物萃取过程的局限性。将CO2高压萃取烟叶中茄尼醇的正交试验数据进行预处理,经过确定隐含节点数、模型的训练、模型的测试等步骤建立了人工神经网络的EBP(Error Back Propagation)模型。模拟结果与...阐述了传统动力学模型用以描述天然产物萃取过程的局限性。将CO2高压萃取烟叶中茄尼醇的正交试验数据进行预处理,经过确定隐含节点数、模型的训练、模型的测试等步骤建立了人工神经网络的EBP(Error Back Propagation)模型。模拟结果与试验结果得到了吻合得很好,为CO2高压萃取烟叶中茄尼醇的工艺设计与优化提供了理论依据,并且显示出人工神经网络在超临界或高压流体萃取的过程模拟中的技术优势,从而展示了人工神经网络在超临界或CO2高压萃取天然产物技术中的应用前景。展开更多
Herein, we report an unprecedented regiospecific oxidative Mizoroki-Heck type reaction for the synthesis of α-difluoromethyl homoallylic alcohols. The reaction shows broad substrate scopes and high functional group t...Herein, we report an unprecedented regiospecific oxidative Mizoroki-Heck type reaction for the synthesis of α-difluoromethyl homoallylic alcohols. The reaction shows broad substrate scopes and high functional group tolerance. Late-stage functionalization of complex biologically active molecules demonstrates the synthetic potential of this transformation. Mechanistic study supports the involvement of MnBr_(2) catalyzed radical 1,2-silyl transfer.展开更多
文摘Density （ρ） and viscosity （η） measurements were carried out for 4-aminobutyric acid in 0.0041,0.0125 and 0.0207 mol·L-1 aqueous salbutamol sulphate at T=308.15,313.15 and 318.15K.The measured values of density and viscosity were used to estimate some important parameters such as apparent molar volume Vφ,limiting apparent molar volume Vφ0,transfer volume △Vφ0,hydration number Hn,second derivative of infinite dilution of partial molar volume with temperature 2Vφ0/T2,viscosity B-coefficients,variation of B with temperature dB/dT,free energy of activation per mole of solvent △μ10＊ and solute △μ20＊,activation entropy △S20＊ and activation enthalpy △H20＊ of the amino acids.These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.
基金Supported by the National Natural Science Foundation of China(No.20673080)the Scientific Research Fund of Xi’an Polytechnic University of China(No.BS0704)
文摘Over the full range of compositions, in the ternary-pseudo-binary mixtures of x[（1-y）C6H5CH=CH2＋ yCH3COOC2H5（or C6H6）]＋（1-x）[（1-y）NMP＋yCH3COOC2Hs（or C6H6）], the apparent molar volumes of each pseudo-pure component at different y values were calculated from the density data at 298.15 K and atmospheric pressure. The results show that the four parameters cubic polynomial can correlate the apparent molar volume with the molar fraction well over the full molar fraction range. The limiting partial molar volumes and the molar volumes of each pseudo-pure component were evaluated with different methods. Based on the limiting partial molar volume and molar volume at a certain y value, a new universal coefficient termed as solvation coefficient γ was defined to describe quantitatively the solvation degree of pseudo-pure solute and the interactions of solute-solvent molecules from the macroscopical thermodynamics viewpoint. The results demonstrate the solvation coefficients decrease with the amount of the third component increasing for each pseudo-pure solute, irrespective of the pseudo-pure solvent. Then the solvation degrees of each pseudo-pure component, the specific interactions between the solute molecule and the solvent one were discussed in terms of the solvation coefficient.
文摘阐述了传统动力学模型用以描述天然产物萃取过程的局限性。将CO2高压萃取烟叶中茄尼醇的正交试验数据进行预处理,经过确定隐含节点数、模型的训练、模型的测试等步骤建立了人工神经网络的EBP(Error Back Propagation)模型。模拟结果与试验结果得到了吻合得很好,为CO2高压萃取烟叶中茄尼醇的工艺设计与优化提供了理论依据,并且显示出人工神经网络在超临界或高压流体萃取的过程模拟中的技术优势,从而展示了人工神经网络在超临界或CO2高压萃取天然产物技术中的应用前景。
基金the National Natural Science Foundation of China (No. 21901191)the Fundamental Research Funds for the Central Universities and Wuhan University for financial support
文摘Herein, we report an unprecedented regiospecific oxidative Mizoroki-Heck type reaction for the synthesis of α-difluoromethyl homoallylic alcohols. The reaction shows broad substrate scopes and high functional group tolerance. Late-stage functionalization of complex biologically active molecules demonstrates the synthetic potential of this transformation. Mechanistic study supports the involvement of MnBr_(2) catalyzed radical 1,2-silyl transfer.
