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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Free energies for degradation reactions of 1,2,3-trichloropropane from ab initio electronic structure theory
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Free energies for degradation reactions of 1,2,3-trichloropropane from ab initio electronic structure theory

机译：从头算电子结构理论看1,2,3-三氯丙烷降解反应的自由能

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Electronic structure methods were used to calculate the gas and aqueous phase reaction energies for reductive dechlorination (i.e., hydrogenolysis), reductive β-elimination, dehydrochlorination, and nucleophilic substitution by OH~- of 1,2,3-trichloropropane. The thermochemical properties ΔH_f°(298.15 K), S°(298.15 K, 1 bar), and ΔG _S(298.15 K, 1 bar) were calculated by using ab initio electronic structure calculations, isodesmic reactions schemes, gas-phase entropy estimates, and continuum solvation models for 1,2,3-trichloropropane and several likely degradation products: CH_3-CHCl-CH_2Cl, CH _2Cl-CH_2-CH_2Cl, C~?H _2-CHCl-CH_2Cl, CH_2Cl-C~?H-CH _2Cl, CH_2=CCl-CH_2Cl, cis-CHCl=CH-CH _2Cl, trans-CHCl=CH-CH_2Cl, CH_2=CH-CH _2Cl, CH_2Cl-CHCl-CH_2OH, CH_2Cl-CHOH- CH_2Cl, CH_2=CCl-CH_2OH, CH_2=COH- CH_2Cl, cis-CHOH=CH-CH_2Cl, trans-CHOH=CH-CH_2Cl, CH(=O)-CH_2-CH_2Cl, and CH_3-C(=O)-CH _2Cl. On the basis of these thermochemical estimates, together with a Fe(II)/Fe(III) chemical equilibrium model for natural reducing environments, all of the reactions studied were predicted to be very favorable in the standard state and under a wide range of pH conditions. The most favorable reaction was reductive β-elimination (ΔG_(rxn)~° ≈ -32 kcal/mol), followed closely by reductive dechlorination (Δ _(Grxn)~° ≈ -27 kcal/mol), dehydrochlorination (Δ_(Grxn)~° ≈ -27 kcal/mol), and nucleophilic substitution by OH~- (Δ_(Grxn)~° ≈ -25 kcal/mol). For both reduction reactions studied, it was found that the first electron-transfer step, yielding the intermediate C~?H _2-CHCl-CH_2Cl and the CH_2Cl-C ~?H-CH_2Cl species, was not favorable in the standard state (Δ_(Grxn)~° ≈ +15 kcal/mol) and was predicted to occur only at relatively high pH values. This result suggests that reduction by natural attenuation is unlikely.
机译：使用电子结构方法来计算气相和水相反应能，以进行1,2,3-三氯丙烷的还原性脱氯（即氢解），还原性β-消除，脱氯化氢和亲核取代。热化学性质ΔH_f°（298.15 K），S°（298.15 K，1 bar）和ΔG_S（298.15 K，1 bar）是使用从头算电子结构计算，等渗反应方案，气相熵估算， 1,2,3-三氯丙烷和几种可能的降解产物的连续溶剂化模型：CH_3-CHCl-CH_2Cl，CH _2Cl-CH_2-CH_2Cl，C〜？H _2-CHCl-CH_2Cl，CH_2Cl-C〜？H-CH _2Cl ，CH_2 = CCl-CH_2Cl，顺式CHCl = CH-CH _2Cl，反式CHCl = CH-CH_2Cl，CH_2 = CH-CH _2Cl，CH_2Cl-CHCl-CH_2OH，CH_2Cl-CHOH-CH_2Cl，CH_2 = CCl-CH_2OH，CH_2 = COH-CH_2Cl，顺式-CHOH = CH-CH_2Cl，反式-CHOH = CH-CH_2Cl，CH（= O）-CH_2-CH_2Cl和CH_3-C（= O）-CH_2Cl。根据这些热化学估算值以及用于自然还原环境的Fe（II）/ Fe（III）化学平衡模型，可以预测所有研究的反应在标准状态和宽pH值下均非常有利。条件。最有利的反应是还原性β-消除（ΔG_（rxn）〜°≈-32 kcal / mol），紧接着是还原性脱氯（Δ_（Grxn）〜°≈-27 kcal / mol），脱氯化氢（Δ_（Grxn） ）〜°≈-27 kcal / mol），并通过OH〜-（Δ_（Grxn）〜°≈-25 kcal / mol）进行亲核取代。对于所研究的两种还原反应，发现第一步电子转移步骤产生的中间体C〜？H _2-CHCl-CH_2Cl和CH_2Cl-C〜？H-CH_2Cl物种在标准状态下不利（Δ_ （Grxn）〜°≈+15 kcal / mol），据预测仅在相对较高的pH值下才会发生。该结果表明通过自然衰减的降低是不可能的。

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