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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 2
BKCSDE 30(2)
February 20, 2009 

A Kinetic Study on Solvolysis of Diphenyl Thiophosphorochloridate
Han Joong Koh*, Suk Jin Kang, Dennis N Kevill
Diphenyl thiophosphorochloridate, Extended Grunwald-Winstein equation, SN2 mechanism
Rates of solvolyses of diphenyl thiophosphorochloridate ((PhO)2PSCl, 1) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone and 2,2,2-trifluoroethanol (TFE) are reported. For four representative solvents, studies were made at several temperatures and activation parameters were determined. The 30 solvents gave a reasonably precise extended Grunwald-Winstein plot, correlation coefficient (R) of 0.989. The sensitivity values (l = 1.29 and m = 0.64) of diphenyl thiophosphorochloridate ((PhO)2PSCl, 1) were similar to those obtained for diphenyl phosphorochloridate ((PhO)2POCl, 2), diphenylphosphinyl chloride (Ph2POCl, 3) and diphenylthiophosphinyl chloride (Ph2PSCl, 4). As with the previously studied of 3~4 solvolyses, an SN2 pathway is proposed for the solvolyses of diphenyl thiophosphorochloridate (1). The activation parameters, ΔH≠ (= 11.6~13.9 kcal?mol-1) and ΔS≠ (= -32.1 ~ -42.7 cal?mol-1?K-1), were determined, and they were in line with values expected for an SN2 reaction. The large kinetic solvent isotope effects (KSIE, 2.44 in MeOH/MeOD and 3.46 in H2O/D2O) are also well explained by the proposed SN2 mechanism.
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