| 李强根,毛双,蔡皖飞,郑 妍,刘柳斜.化学通报,2016,79(5):418-424. |
| 卤素离子与卤代苯气相SNAr反应理论研究 |
| Theoretical Studies on the Gas-Phase SNAr Reactions of Halobenzenes and Halide Anions |
| 投稿时间：2015-08-12 修订日期：2015-10-19 |
| DOI： |
| 中文关键词: SNAr反应 亲核试剂 反应性 B3LYP 反应机理 |
| 英文关键词:SNAr reaction, Nucleophile, Reactivity, B3LYP, Reaction mechanism |
| 基金项目:四川省教育厅基金（批准号：13ZB0160） |
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| 中文摘要: |
| 采用B3LYP/6-311+G**和MP2/6-311+G**方法,对卤素离子与卤代苯气相SNAr反应(ArY + X－ = ArX + Y－, X, Y = F, Cl, Br和I)作了全面理论研究。结果显示：气相里除了X, Y = F, F反应为分步路径外,其余反应通道都是协同SNAr机理；F离子进攻卤苯SNAr反应无论从动力学(ΔGb = 9.0 ~ 17.3 kJ/mol)还是热力学上来说都很容易进行,然而Cl、Br和I离子进攻的反应,其MP2吉布斯自由能垒(ΔGb)高达91.3~202.5 kJ/mol,因此在气相里很难发生；另外,标题反应的反应性可以通过卤素离子质子亲和能(PA)、最高占据轨道能(EHOMO)、Mulliken电负性(χ)以及键级(BO)与NPA电荷(Q)来分析,其中过渡态里C─Y键的断裂是引起反应能垒升高的主要因素,亲核试剂的亲核能力主要由最高占据轨道能控制,而卤素离子的离去能力由其质子亲和能或电负性决定。 |
| 英文摘要: |
| Comprehensively investigations on the gas-phase SNAr reactions of halobenzenes and halide anions (ArY X－ = ArX Y－, X, Y = F, Cl, Br and I) were performed by the B3LYP and MP2 methods with the 6-311 G** basis set. Calculated results indicate that the SNAr reactions of halobenzenes and halide anions in the gas-phase proceed via a concerted mechanism, while a two-step addition–elimination pathway is founded with the formation of a stable σ-complex for X, Y = F, F. In view of thermodynamics and kinetics, the gas-phase SNAr reactions of halobenzenes attacked by fluoride ion are easily to proceed (ΔGb = 9.0 ~ 17.3 kJ/mol), whereas it would be hardly possible to observe the reactions for X = Cl－, Br－ and I－ due to the higher overall barriers (ΔGb = 91.3~202.5 kJ/mol). In addition, the reactivity of the title reactions can be analyzed by proton affinity (PA), the highest occupied orbital energy (EHOMO) and Mulliken electronegativity (χ) of the halide as well as the bond order (BO) and NPA charges (Q). The broken of the C─Y bond in TS is mainly responsible for the reaction barriers, and the nucleophilicity of the halide anion nucleophile is mainly dominated by the highest occupied orbital energy, while the leaving-group ability of halogen anion is governed by proton affinity or Mulliken electronegativity. |
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