A Study on the Hydrolysis of Sarin and Soman by Merrifield-Type Diaminatedpolystyrene-Cu (II) Heterogeneous Polymers

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Journal of the Korea Institute of Military Science and Technology 2000;3(1):164-175.

Merrifield-Type Diaminatedpolystyrene-Cu (II) 불균일 촉매에 의한 Sarin과 Soman 분해반응 연구

정우영, 계영식

육군사관학교 화학과

Abstract

Three compounds of Cu(II)-loaded N,N,N'-trimethylethylenediaminated Merrifield-type polymers were synthesized with yields higher than 80%, and the hydrolysis reaction rates of O-isopropylmethyl-phosphonofluoridate(GB) and O-pinacolylmethylphosphonofluoridate (GD) catalyzed by them have been surveyed. GB and GD hydrolysis by Cu(II)-loaded polymers occurs via intermediate complex mechanism where rapid equilibrium to form intermediate complex between substrate and Cu(II)-loaded polymers($K_f$) is followed by rate determining hydrolysis step($k_1$). The measured activation parameters for $k_1$ are ${Delta}H^{ddag}$ : $17.75{pm}0.98kJ/mol$ ${Delta}S^{ddag}$ / : $-218.42{pm}3.35J/mol$ K, $E^{circ}_a$ : $20.22{pm}0.98kJ/mo1$ for GB and ${Delta}H^{ddag}$ / : $11.16{pm}1.15kJ/mol,$${Delta}S^{ddag}$ /: $-258.57{pm}3.93J/mol$ K, $E^{circ}_a$ : $13.64{pm}1.15 kJ/mol$ for GD. Standard enthalpy/entropy changes corresponding to the intermediate complex formation constant $K_f$ are ${Delta}H^{circ}$ : $37.05{pm}2.19 kJ/mo1,$$ {Delta}S^{circ}$ : $163.12{pm}7.49 J/mol$ K and ${Delta}H^{circ}$ : 418.59{pm}2.04 kJ/mol,$ ${Delta}S^{circ}$ : 4111.92{pm}6.98 J/mol$ K for GB and GD, respectively, The electron push-pull mechanism by Cu(II)-loaded polymers lowers the P-F bond breaking energy(~400 kJ/mol) to less than 1/20 compared to the case in which no Cu(II)-loaded resin presents. Analysis of $K_f$ and 4k_1$ over pH=6.5~8.0 range suggest that the GB and GD hydrolysis occurs intramolecularily with $pK_a$ =7.29 for ligated $H_2O$ and $t_{1/2}$=36.9 sec, $pK_a$ = 7.06 and $t_{1/2}$=177.7 sec for GB and GD, respectively.

Key Words: Sarin, Soman, Hydrolysis, Polymer Catalyst. Cu(II)