Single transition state in the transfer of a neutral phosphoryl group between phenoxide ion nucleophiles in aqueous solution

1990 ◽  
Vol 112 (22) ◽  
pp. 8115-8120 ◽  
Author(s):  
Salem A. Ba-Saif ◽  
Mark A. Waring ◽  
Andrew Williams
Keyword(s):  
Aqueous Solution ◽  
Transition State ◽  
Phosphoryl Group ◽  
Single Transition

A single transition state in the reaction of aryl diphenylphosphinate esters with phenolate ions in aqueous solution

1988 ◽  
Vol 110 (6) ◽  
pp. 1890-1895 ◽  
Author(s):  
Nicholas. Bourne ◽  
Edwin. Chrystiuk ◽  
Andrew M. Davis ◽  
Andrew. Williams
Keyword(s):  
Aqueous Solution ◽  
Transition State ◽  
Single Transition

Ligand substitution at five-coordinate copper(II) centres by cyanate, chloride and bromide ions

1980 ◽  
Vol 33 (6) ◽  
pp. 1381 ◽  
Author(s):  
JH Coates ◽  
PR Collins ◽  
SF Lincoln
Keyword(s):  
Aqueous Solution ◽  
Transition State ◽  
Ligand Substitution ◽  
Aqua Ligand ◽  
Stopped Flow ◽  
Bromide Ions ◽  
Ethyl Amine ◽  
Ligand Bond

The substitution of the aqua[tris{2-(dimethylamino)ethyl}amine]copper(II) ion by cyanate, chloride and bromide ions has been studied in aqueous solution by static and stopped-flow spectrophoto-metric techniques. This process is unusually slow for ligand substitution at a copper(II) centre and appears to proceed through an interchange mechanism in which the copper(II)-aqua ligand bond makes a major contribution to the transition state energetics.

Phosphotransfer and Nucleotidyltransfer

2007 ◽  
Author(s):  
Perry A. Frey ◽  
Adrian D. Hegeman
Keyword(s):  
Transition State ◽  
Molecular Mechanisms ◽  
Enzymatic Reaction ◽  
Covalent Bond ◽  
Phosphoryl Group ◽  
Dissociative Mechanism ◽  
Chemical Mechanisms ◽  
Cellular Processes ◽  
Nucleic Acid Biosynthesis ◽  
Transfer Mechanisms

Phosphotransferases, phosphatases, and nucleotidyltransferases catalyze nucleophilic substitution at phosphorus. They constitute a dominant class of enzymes in intermediary metabolism, energy transduction, nucleic acid biosynthesis and processing, and regulation of many cellular processes, including replication, cellular development, and apoptosis. The mechanisms of the action of these enzymes have been studied intensively at several levels, ranging from the biosynthesis of metabolites and nucleic acids to unmasking signaling networks to elucidating the molecular mechanisms of catalysis. We focus on the chemical mechanisms of the reactions of biological phosphates. More than 40 years of research on this chemistry reveals that the mechanisms can be grouped into two classes: the phosphoryl group (PO3−) transfer mechanisms and the nucleotidyl or alkylphosphoryl group (ROPO2−) transfer mechanisms. Because the fundamental chemical mechanisms of these reactions are not treated in textbooks, we begin by considering this chemistry and then move on to the enzymatic reaction mechanisms. Phosphomonoesters, phosphoanhydrides, and phosphoramidates undergo substitution at phosphorus by transfer of the phosphoryl (PO3–) group, that is, by P—O and P—N cleavage. The current description of a typical phosphoryl group transfer mechanism is one in which the phosphoryl donor and acceptor interact weakly with the phosphoryl group in flight in a transition state in which the total bonding to phosphorus is decreased relative to the ground state. The bonding is weak between phosphorus and the leaving group R–X and between phosphorus and the accepting group Y in the transition state of. Because of decreased bonding to phosphorus, this is a loose transition state that has been described as dissociative. The latter should not be confused with the dissociative mechanism, which is considered later. To avoid confusion, we use the term loose transition state. Detailed studies indicate that the bonding denoted by the dashed lines in represents partial covalency on the order of 10% to 20% of the strength of a full covalent bond, or a bond order of 0.1 to 0.2.

Sign in / Sign up

Export Citation Format

Share Document