利用理論計算探討酮類與烯醇間之轉換的反應機制與動力學分析

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Title:	利用理論計算探討酮類與烯醇間之轉換的反應機制與動力學分析 Mechanistic and kinetic studies of the conversion reaction between ketones and enols: insight from First-Principles calculations
Authors:	邱浩瑜
Contributors:	化學系應用化學碩士班
Keywords:	活化能 Activation energy
Date:	2023
Issue Date:	2023-08-02 15:13:29 (UTC+8)
Abstract:	通過理論計算的方法來探討酮類轉換成稀醇的過程，改變取代基來觀察活化能之間的差異，找出何種取代基具有較低之活化能及討論何種取代基其產物最穩定。利用Gaussian 09W的計算軟體，搭配高層級的B3lyp/6-311++G(3df,2p)來獲得更精準的數據。所使用的取代基有:CH3、NH2、F、Cl、Br五種，嘗試改變取代基的數量來達到降低過渡態活化能的目的。由計算結果觀察，我們得知當有1個取代基時，取代基為NH2時的反應活化能會是最低，該Ea數值為64.04 kcal/mol。在2個取代基與3個取代基時，反應活化能最低的變成CH3取代的分子，數值分別為63.08 kcal/mol以及62.97 kcal/mol，故我們推測取代基若為推電子基有利於反應的進行。接著，我們進行動力學與Fukui function的計算，在動力學計算方面，我們可以看出含有CH3和NH2推電子基與其他拉電子基的分子在不同取代基的數量相比都具有較好的反應速率，而這項趨勢隨著取代基的增加有明顯上升，這項數據有助於證明我們對於活化能反應的實驗數據。再來利用Fukui function的計算我們可以發現當C含有推電子的取代基時，解離氫的C原子其f+的值會大於含有拉電子取代基的C，這項數值代表了推電子基會使H 容易進行氫的轉移，並有助於反應的進行。 This research uses the method of theoretical calculation to investigate the process of converting ketones into enols. By changing the substituents, we will observe the difference in activation energy and find out which substituent molecule has a lower activation energy. We will focus on discussing which structure of the substituent has the best effect to produce enol. This study will use the chemical calculation software of Gaussian 09W, together with the high-level calculation level B3LYP/6-311++G(3df,2p) to enable us to obtain more accurate data. The substituents we used here are CH3, NH2, F, Cl, Br five kinds, and try to change the number of substituents to achieve the purpose of reducing the activation energy of the reaction. Next, we go to the calculation of dynamics and Fukui function. In terms of kinetic calculations, we can see that molecules containing CH3 and NH2 electron-pushing groups have better reaction rates than molecules with other electron-withdrawing groups in terms of the number of different substituents. This trend increases significantly with the increase of substituents, which helps to support our experimental data on the activation energy response. Then, using the Fukui function calculation method, we can find that when C contains electron-pushing substituents, the f+ value of the C atom that dissociates hydrogen will be greater than that of C containing electron-pull substituents. This value represents the electron-pull substituent that makes H+ easy to dissociate and carry out the transfer of H, which is helpful for the reaction to proceed.
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