86260-32-4Relevant academic research and scientific papers
Bonding in Phosphoryl (-PO32-) and Sulfuryl (-SO3-) Group Transfer between Nitrogen Nucleophiles as Determined from Rate Constants for Identity Reactions
Williams, Andrew
, p. 6335 - 6339 (2007/10/02)
Rate constants have been measured for the bimolecular reactions of pyridines with pyridinium-N-phosphonates (kyxp) and pyridinium-N-sulfonates (kyxs) for aqueous solution at 25 deg C and 0.1 M ionic strength.The Broensted correlations with the pK of the entering or leaving pyridine can be used to calculate the rate constants for reactions where entering and leaving pyridines are identical.The Broensted selectivities of the "identity" rate constants (βi=-0.53 for kxxp and βi=-55 for kxxs) predict tightness parameters (τ) of 0.35 and 0.56 and bond orders (η) of 0.17 and 0.28 for the N-P and N-S bonds in the transition states for the transfer processes.The data are consistent with first-order "Marcus" theory governing the energy surfaces of the reactions and in particular obey the relationship βi=βnuc+βlg predicted by Lewis and Hu.
Single Transition State for Sulfuryl Group (-SO3-) Transfer between Pyridine Nucleophiles
Bourne, Nicholas,Hopkins, Andrew,Williams, Andrew
, p. 4327 - 4331 (2007/10/02)
The second-order rate constants for the nucleophilic attack of pyridines on isoquinoline-N-sulfonate (25 deg C, 0.1 M ionic strength) obey an excellent linear relation, log kXpyisq = 0.23 pKXpy - 1.91 (r=0.995), with the pK of the attacking - equation - pyridine over eight pK units.The complete absence of curvature in the relationship indicates a single transition state for the reaction consistent with a concerted, symmetrical mechanism.The attack of pyridine on substituted pyridine-N-sulfonates (25 deg C, ionic strength at 0.1 M) obeys the Bronsted equation log KpyXpy = -0.9 pKXpy + 4.22 (r=0.998).The ΒEQ for the equilibrium transfer of the -SO3- group from a constant pyridine leaving group to a variant pyridine nucleophile ( +1.13) is close to that predicted from a previous study.The electronic structure of the transition state possesses considerable sulfur trioxide character as deduced from the changes in effective charge on the entering and leaving pyridine nitrogen atoms.
