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首页> 外文期刊>ACS Omega >Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
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Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation

机译：验证部分酰胺键旋转中的焓熵补偿机制

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The concept of enthalpy–entropy compensation (EEC) is one of the highly debated areas of thermodynamics. The conformational change due to restricted double-bond rotation shows a classic two-site chemical exchange phenomenon and has been extensively studied. Fifty-four analogs of N ,N -diethyl-m -toluamide (DEET) as a model system were synthesized to study the thermodynamics of the partial amide bond character using nuclear magnetic resonance (NMR) spectroscopy. Line-shape analysis as a function of temperature is used to estimate the chemical exchange. Eyring analysis was then used to convert the chemical exchange rates to determine the transition state enthalpy and entropy of the molecules. The experimental design follows selective variations that perturb one aspect of the molecular system and its influence on the observed thermodynamic effect. The results of the study demonstrate that amide bond resonance in analogs of DEET follows an EEC mechanism. Simple modifications made to DEET’s structural motif alter both the enthalpy and entropy of the system and were limited overall to a temperature compensation factor, T _(β) = 292.20 K, 95% CI [290.66, 293.73]. We suggest EEC as a model to describe the kinetic compensation seen in chemical exchange phenomena in analogs of DEET.
机译：焓熵补偿（EEC）的概念是热力学高度争论的区域之一。由于受限制的双键旋转引起的构象变化显示了经典的双站点化学交换现象，并已被广泛研究。合成了五十四种的 N， N-二乙基 - m-唑胺（DEET）作为模型系统，以研究使用核磁共振（NMR）光谱法的部分酰胺键特征的热力学。线形分析作为温度的函数用于估计化学交换。然后用于转换化学汇率以确定分子的过渡状态焓和熵的化学汇率分析。实验设计遵循扰动分子系统的一个方面的选择性变化及其对观察到的热力学效应的影响。该研究的结果表明，DEET类似物中的酰胺键共振遵循EEC机制。对DEET结构基质的简单修改改变了系统的焓和熵，并且总体上限于温度补偿因子， T_（β）= 292.20k，95％CI [290.66,293.73]。我们建议EEC作为描述DEET类似物中化学交换现象中看到的动力学补偿的模型。

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