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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 10
BKCSDE 30(10)
October 20, 2009 

 
Title
Kinetic Studies of the Solvolyses of 4-Nitrophenyl Phenyl Thiophosphorochloridate
Author
Han Joong Koh*, Suk Jin Kang
Keywords
4-Nitrophenyl phenyl thiophosphorochloridate, Extended Grunwald-Winstein equation, SN2 mechanism, Kinetic solvent isotope effects
Abstract
Rates of solvolyses of 4-nitrophenyl phenyl thiophosphorochloridate (4-NO2PhOP(S)(Cl)OPh, 1) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone, and 2,2,2-trifluroethanol (TFE) are reported. Thermodynamic parameters were determined at several temperatures in three representative solvents. The extended Grunwald-Winstein equation was applied to 29 solvents and the correlation coefficient (R) showed 0.959. The sensitivities (l = 1.37 and m = 0.62) are similar to those obtained for diphenyl thiophosphorochloridate ((PhO)2PSCl, 2), diphenyl phosphorochloridate ((PhO)2POCl, 3), diphenyl phosphinic chloride (Ph2POCl, 4), and diphenyl thiophosphinic chloride (Ph2PSCl, 5). The solvolytic reaction mechanism of 4-nitrophenyl phenyl thiophosphorochloridate (1) is suggested to be proceeded a SN2 process as previously reported result. The activation enthalpies are shown as slightly low as ΔH≠ = 9.62 to 11.9 kcal·mol-1 and the activation entropies are shown as slightly high negative value as ΔS≠ = -34.1 to -44.9 cal·mol-1·K-1 compared to the expected SN2 reaction mechanism. Kinetic solvent isotope effects are accord with a typical SN2 mechanism as shown in the range of 2.41 in MeOH/ MeOD and 2.57 in H2O/D2O solvent mixtures.
Page
2413 - 2418
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