title: Theoretical study of the importance of the spectator groups on the hydrolysis of phosphate triesters.
abstract: The spontaneous hydrolysis of a series of five triaryl and two dialkyl aryl phosphate triesters, previously studied experimentally, is examined theoretically using two different hybrid density functional methods, B3LYP and M06; two basic sets, 6-31+G(d) and 6-311++G(d,p); and the Gaussian 09 program. The B3LYP/6-31+G(d) methodology combined excellent accuracy with minor computational cost. The calculations show excellent quantitative agreement with experiment, which is best in the presence of three discrete water molecules. The results support a two-step mechanism involving a pentacovalent addition intermediate, with a lifetime of tenths of a millisecond. The rate-determining formation of this intermediate involves general base catalysis, defined by concerted proton transfers in a six-membered cyclic activated complex (TS1), which involves two hydrogen-bonded water molecules supporting a well-developed H(2)O···P bond (mean % evolution 77.83 ± 0.97). The third water molecule is hydrogen-bonded to P═O and subsequently involved in product formation via TS2. The effects on reactivity of all the groups attached to phosphorus in TS1 are examined in detail: the two non-leaving groups in particular are found to play an important role, accounting for the substantial difference in reactivity between triaryl and dialkyl aryl phosphate triesters.
authors: Department of Chemistry, National Institute of Catalysis, Federal University of Santa Catarina, Florianópolis, Santa Catarina 88040-900, Brazil.
authors: José R
authors: JR
authors: Mora
authors: Anthony J
authors: AJ
authors: Kirby
authors: Faruk
authors: F
authors: Nome
mesh_terms: D002384:Catalysis; D003198:Computer Simulation; D006860:Hydrogen Bonding; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D015394:Molecular Structure; D010755:Organophosphates / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D011522:Protons; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D010755:Organophosphates; D011522:Protons; D014867:Water; D010758:Phosphorus