单嘧磺隆除草剂的晶体构象-活性构象转换的密度泛函理论研究

应用密度泛函理论在B3LYP/6-31G(d)水平上对新型除草剂单嘧磺隆绕脲桥部分两个C—N键的内旋转势能面进行计算, 然后对势能面上的驻点进行构型优化和过渡态搜索, 得到单嘧磺隆4种稳定构象和构象转换过程所涉及的8个过渡态结构. 研究结果表明, 单嘧磺隆晶体构象-活性构象转换过程中涉及4种稳定构象和8条转换途径, 脲桥部分NH基团与嘧啶环上N原子所形成的分子内氢键对于构象的稳定性及转换过程起着十分重要的作用. 应用极化连续介质溶剂模型(PCM)在B3LYP/6-31＋＋G(d, p)水平下进行溶剂化效应计算, 结果表明单嘧磺隆从晶体构象转换成活性构象主要是在水相中进行的.     

单嘧磺隆除草剂水解机理的理论研究

用量子化学中密度泛函B3LYP方法在6-31G*水平上, 对单嘧磺隆的水解机理进行了理论研究. 优化了反应过程中反应物、中间体、过渡态及产物的几何构型, 并对各个过渡态和中间体进行了振动分析确认其真实性. 结果表明: 在碱性条件下, 水解反应主要经历一个五元环的过渡态TS1, 该反应速控步骤的能垒为25.7 kJ/mol; 在中性条件下, 水解反应涉及到一个三元环的过渡态和两个四元环的过渡态, 反应的速控步骤为M3'＋H₂O→TS2', 能垒为236.5 kJ/mol. 从能量上看, 碱性条件更有利于水解反应的进行, 与实验结果吻合. 同时, 我们还考虑了溶剂效应对水解反应的影响.     

Synthesis and Crystal Structure of Sodium Monosulfuron (N-(4-Methylpyrimidin-2-yl)-N'-2-(nitrophenylsulfonyl) Urea Sodium)

Monosulfuron is a novel sulfonylurea herbicide with ultra-low dosage invented and patented by Nankai University.Herein its sodium salt was firstly synthesized and crystal structure was determined by X-ray diffraction method.The title compound belongs to the triclinic system, space group P1- with a = 7.306(6), b = 9.446(8), c = 11.872(10)(A), α= 76.578(14), β= 78.049(13), γ= 77.620(14)°, V = 767.7(11)(A)3, Mr = 377.32, Z = 2, Dc = 1.632 g/cm3,μ= 0.283 mm-1, F(000) = 388, R = 0.0444 and wR = 0.1186.In the title compound, Na(1) coordinates with O(4) and O(5) from one monosulfuron molecule, N(4A) and O(5A) from the other monosulfuron molecule and the oxygen atom from H2O to give five coordination bonds.The title complex is further linked into a three-dimensional structure through π…π interactions and intermolecular hydrogen bonds between the oxygen and nitrogen atoms.     

Synthesis and Crystal Structure of Sodium Monosulfuron （N-（4-Methylpyrimidin-2-yl）-N＇-2-（nitrophenylsulfonyl） Urea Sodium）

ABSTRACT Monosulfuron is a novel sulfonylurea herbicide with ultra-low dosage invented and patented by Nankai University. Herein its sodium salt was firstly synthesized and crystal structure was determined by X-ray diffraction method. The title compound belongs to the triclinic system, space group P1^- with a = 7.306（6）, b = 9.446（8）, c = 11.872（10）A, α = 76.578（14）, β = 78.049（13）, γ = 77.620（14）°, V = 767.7（11）A^3, Mr = 377.32, Z = 2, Dc = 1.632 g/cm^3,μ= 0.283 mm^-1, F（000） = 388, R = 0.0444 and wR = 0.1186. In the title compound, Na（1） coordinates with 0（4） and 0（5） from one monosulfuron molecule, N（4A） and O（5A） from the other monosulfuron molecule and the oxygen atom from H2O to give five coordination bonds. The title complex is further linked into a three-dimensional structure through π…π interactions and intermolecular hydrogen bonds between the oxygen and nitrogen atoms.     

Theoretical Study on the Structures,Spectra and Thermodynamic Property of Herbicidal Monosulfuron

The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound's structure-activity relationship.