Direct measurement of transition-state bond cleavage in hydrolysis of phosphate esters of p-nitrophenol

1990 ◽  
Vol 112 (20) ◽  
pp. 7421-7422 ◽  
Author(s):  
Alvan C. Hengge ◽  
W. W. Cleland
Keyword(s):  
Transition State ◽  
Direct Measurement ◽  
Bond Cleavage ◽  
Phosphate Esters ◽  
Hydrolysis Of

Transition-state structure for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride

2015 ◽  
Vol 93 (4) ◽  
pp. 463-467 ◽  
Author(s):  
Jefferson Chan ◽  
Ariel Tang ◽  
Andrew J. Bennet
Keyword(s):  
Transition State ◽  
Kinetic Isotope Effect ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Theoretical Modelling ◽  
Kinetic Isotope ◽  
Hydronium Ion ◽  
Anomeric Carbon ◽  
Hydrolysis Of

The transition state for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride in water has been characterized by combining multiple kinetic isotope effect measurements with theoretical modelling. The measured kinetic isotope effects for the C1-deuterium, C2-deuterium, C5-deuterium, anomeric carbon-13, and ring oxygen-18 are 1.219 ± 0.021, 1.099 ± 0.024, 0.976 ± 0.014, 1.014 ± 0.005, and 0.991 ± 0.013, respectively. The transition state for the hydronium ion reaction is late with respect to both C–F bond cleavage and proton transfer.

Kinetics and mechanism of the hydrolysis of a (5,6)-spirophosphorane. Thermodynamics of the hydrolysis of cyclic five-membered and six-membered phosphonium ions

1991 ◽  
Vol 69 (12) ◽  
pp. 2064-2074 ◽  
Author(s):  
Glenn H. McGall ◽  
Robert A. McClelland
Keyword(s):  
Free Energy ◽  
Transition State ◽  
Rate Constants ◽  
Strong Acid ◽  
Membered Ring ◽  
Phosphate Esters ◽  
Hydrolysis Rate ◽  
Activation Free Energy ◽  
Stabilizing Effect ◽  
Hydrolysis Of

The cyclic five-membered phosphonium ion 2b (2-(2′-hydroxyethoxy)-2-phenyl-1,3,2-dioxaphospholan-2-ylium) derived from ring-opening of the (5,5)-spirophosphorane 1b (5-phenyl-1,4,6,9-tetraoxa-5-phosphaspiro[4,4]nonane) has been observed in neat CF3SO3H and at >85% H2SO4. The cation undergoes hydrolysis in the latter solutions, and an extrapolation has been carried out to obtain an estimate for reactivity in 100% water. Hydrolysis rate constants for phenyltrialkoxyphosphonium ions in water are 107, 100, and 5 × 10−3 s−1 for cyclic five-membered, cyclic six-membered, and acyclic derivatives respectively; these show an excellent correlation with rate constants for a similar series of phosphate esters. An investigation of the hydrolysis of the (5,6)-spirophosphorane 5 (5-phenyl-8,8-dimethyl-1,4,6,10-tetraoxa-5-phosphaspiro[4,5]decane) provides a clue as to the origins of these rate differences. This phosphorane can in principle hydrolyze via two isomeric cyclic phosphonium ions, the six-membered 14 and the five-membered 15. The former is thermodynamically more stable, being the only cation observed under equilibrating conditions of strong acid. However, the hydrolysis of the spirophosphorane, as well as the hydrolysis of fully formed 14, channels through the cyclic five-membered 15. A thermodynamic breakdown reveals that the 9.5 kcal mol−1 difference in activation free energy for the hydrolysis of five- and six-membered cyclic phosphonium ions is due to a combination of a higher free energy (2.5–4.5 kcal mol−1) for the five-membered cation, and a lower free energy (7–5 kcal mol−1) for the pentacoordinate transition state with the five-membered ring. This analysis also shows that a (5,6)-spirophosphorane is 6–8 kcal mol−1 more stable than a (6,6)-spirophosphorane. Thus, a five-membered ring has a significant stabilizing effect on a pentacoordinated phosphorus structure. The accelerated hydrolysis of cyclic phosphonium ions and phosphate esters with five-membered rings is caused by a combination of this stabilizing effect in the transition state and a destabilizing effect in the ground state associated with ring strain. Key words: phosphorane, hydrolysis, phosphate, phosphonium.

Transition state activity coefficients in the acid-catalyzed hydrolysis of amides

1977 ◽  
Vol 55 (16) ◽  
pp. 3050-3057 ◽  
Author(s):  
Tomasz A. Modro ◽  
Keith Yates ◽  
Françoise Beaufays
Keyword(s):  
Transition State ◽  
Bond Cleavage ◽  
Protonated Form ◽  
State Activity ◽  
Alkyl Derivatives ◽  
Amide Hydrolysis ◽  
Conjugate Acid ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Nitrogen Bond

The transition-state activity coefficient [Formula: see text] approach has been applied to the acid-catalyzed hydrolysis of benzamide and its N-alkyl derivatives. For all systems (with the exception of the N-tert-butyl derivative which reacts via carbon–nitrogen bond cleavage) a uniform type of medium dependence of [Formula: see text] is observed. The reaction shows a pronounced destabilization of S≠ over the whole region of acidity studied, practically identical to that found for the AAc-2 type of ester hydrolysis. This is interpreted in terms of an AoT2 mechanism of amide hydrolysis, that is the rate-determining formation of the oxonium-type tetrahedral intermediate from the O-protonated form of substrate conjugate acid.

1-Oxo-2-oxa-1-phosphabicyclo[2.2.2]octane:  A New Mechanistic Probe for the Basic Hydrolysis of Phosphate Esters

1996 ◽  
Vol 118 (42) ◽  
pp. 10168-10174 ◽  
Author(s):  
Andrzej E. Wróblewski ◽  
John G. Verkade
Keyword(s):  
Phosphate Esters ◽  
Mechanistic Probe ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

Nitro–Nitrite Isomerization and Transition State Switching in the Dissociation of Ionized Nitromethane: A Threshold Photoelectron–Photoion Coincidence Spectroscopy Study

2009 ◽  
Vol 15 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Brandon Ferrier ◽  
Anne-Marie Boulanger ◽  
David M.P. Holland ◽  
David A. Shaw ◽  
Paul M. Mayer
Keyword(s):  
Transition State ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Bond Cleavage ◽  
Cleavage Reaction ◽  
Nitrite Ion ◽  
Methyl Nitrite ◽  
Bond Cleavage Reaction ◽  
Entropy Of Activation ◽  
Lower Entropy

Threshold photoelectron–photoion coincidence (TPEPICO) spectroscopy has been employed to investigate the competition between bond cleavage and rearrangement reactions in the dissociation of ionized nitromethane, 1. Modeling TPEPICO breakdown diagrams with a combination of RRKM theory and ab initio calculations at the G3 level of theory allowed the derivation of the activation energy for the isomerisation of 1 to ionized methyl nitrite, 2, 82 kJ mol−1. In addition, evidence was found for a transition state switch in the bond cleavage reaction in 1 leading to CH3• + NO2+. As internal energy increases, the effective transition state for this reaction becomes tighter (i.e. is characterized by a lower entropy of activation, Δ‡S). Fitted thresholds for NO+ and CH2OHO+ ions, originating from the isomeric methyl nitrite ion, are consistent with G3 level ab initio calculations.

Transition state stabilization by deaminases: Rates of nonenzymatic hydrolysis of adenosine and cytidine

1987 ◽  
Vol 15 (2) ◽  
pp. 100-108 ◽  
Author(s):  
Lloyd Frick ◽  
John P. Mac Neela ◽  
Richard Wolfenden
Keyword(s):  
Transition State ◽  
Transition State Stabilization ◽  
Hydrolysis Of
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