Alkali Metal Ion Catalysis and Inhibition in Nucleophilic Displacement Reactions at Phosphorus Centers: Ethyl and Methyl Paraoxon and Ethyl and Methyl Parathion
We report on the ethanolysis of the PO and PS compounds ethyl and methyl paraoxon (1a and 1b) and ethyl and methyl parathion (2a and 2b). Plots of spectrophotometrically measured rate constants, kobsd versus [MOEt], the alkali ethoxide concentration, show distinct upward and downward curvatures, pointing to the importance of ion-pairing phenomena and a differential reactivity of free ions and ion pairs
我们报道了P O和PS化合物乙基和甲基对氧磷(1a和1b)以及乙基和甲基对硫磷(2a和2b)的乙醇化反应。分光光度法测量的速率常数的曲线,ķ实测值与[MOET],碱浓度乙醇,显示不同的向上和向下的曲率,指向的离子配对现象的重要性和自由离子和离子对的差分的反应性。三种类型的反应性和选择性的图案已经被辨别:(1)对于P Ò化合物1A和1B,LiOEt>的NaOEt> KOEt>环氧乙烷- ; (2)用于P S化合物图2a,KOEt>环氧乙烷- >的NaOEt> LiOEt; (3)对于P S,2B,18C6冠络合KOEt> KOEt =环氧乙烷- >的NaOEt> LiOEt。这些选择性模式取决于亲电中心,P O vs P S和金属阳离子的性质,是碱金属阳离子的催化和抑制的特征。基态(GS)与过渡态(TS)的稳定能为催化和抑制趋势提供了线索。值得注意的是,冠状K +对2b反应的空前催化行为。建模揭示了2a与加冠K
Rate and product studies with dimethyl phosphorochloridate and phosphorochloridothionate under solvolytic conditionsPresented, in part, at the Tenth Kyushu International Symposium on Physical Organic Chemistry, Fukuoka, October 2003. Abstracted in part from the MS thesis of J. S. C., Northern Illinois University, December 1998.
作者:Dennis N. Kevill、Jeffrey S. Carver
DOI:10.1039/b402093f
日期:——
correlated using the extendedGrunwald-Winsteinequation, with incorporation of the NT solvent nucleophilicity scale and the YCl solvent ionizing power scale. The sensitivity parameters (l and m) are similar to each other and also similar to previously recorded values for solvolyses of arenesulfonyl chlorides, which were proposed to follow a concerted displacement mechanism. For solvolyses in aqueous ethanol