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| 研究生： |
陳建成 Chen, Jian-cheng |
|---|---|
| 論文名稱： |
乙醇及三氟乙醇在BMIPF6中物理狀態之分子模擬 Molecular simulations of the physical states of Ethanol and 2,2,2-trifluoroethanol in 1-butyl-3-methylimidazolium hexafluorophoasphate |
| 指導教授： |
施良垣
Shy, Liang-Yuan |
| 學位類別： |
碩士 Master |
| 系所名稱： |
理學院 - 化學系碩士在職專班 Department of Chemistry (on the job class) |
| 論文出版年： | 2009 |
| 畢業學年度： | 97 |
| 語文別： | 中文 |
| 論文頁數： | 94 |
| 中文關鍵詞： | 導電 、擴散 、三氟乙醇 、乙醇 、BMIPF6 、分子動力模擬 |
| 外文關鍵詞： | diffusion, ethanol, trifluoroethanol, Molecular dynamics simulations, BMIPF6, conductivity |
| 相關次數： | 點閱：89 下載：1 |
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本篇以分子動力方法模擬稀釋劑(三氟乙醇、乙醇)分別加入離子液體BMIPF6 後的擴散及導電性質，模擬之溫度為300 K，稀釋劑之莫耳分率分別為0.25、0.45和0.65，並以微觀的角度探討稀釋劑與BMI+、PF6－之作用力。
結果顯示，模擬之擴散係數與比導電度值均隨著稀釋劑的含量增加而上升，且與實驗值相當接近。含三氟乙醇系統之離子擴散速率較快，這可能是因為CF3CH2OH之介電常數與體積較大所致。
當稀釋劑為三氟乙醇時，羥基之O原子與BMI＋離子之H2 原子(五圓環上兩個氮之間的氫原子)會產生氫鍵，且羥基之H原子也會與PF6－離子之F原子產生氫鍵。這些氫鍵作用力均較稀釋劑為乙醇時大，此結果與核磁共振所測得之H2的化學位移較down field的傾向一致。在PF6－離子之F原子的化學位移也發現類似的結果。
自由陽離子與陰離子之比率隨稀釋劑含量之增加而上升，其中以三氟乙醇之效果較好。BMI+ 離子周圍第一殼層PF6－之配位數隨稀釋劑含量之增加而減少，但稀釋劑配位數則遞增，其中以加入三氟乙醇時最大，可能是因為三氟乙醇與BMI+ 離子之氫鍵作用力較大所致。
依據這些分子模擬，本篇描繪出BMI+周圍環境示意圖。這些圖清楚說明離子與稀釋劑的分布情形，對於實驗極具參考價值。
Molecular dynamics simulations have been used to study the diffusion and conductivity properties for diluent 2,2,2-trifluoroethanol (CF3CH2OH) and ethanol (CH3CH2OH) in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIPF6) at 300 K with diluent mole fraction of 0.25, 0.45 and 0.65. The interactions between BMI+ and PF6－ ions were explored from a microscopic point of view.
The simulated diffusion coefficients and specific conductivities increase with the increase of diluent content, the values of which agree well with experiments. The diffusion rate of ions is faster in CF3CH2OH containing system, probably due to large dielectric constant and molecular volume of diluent.
In CF3CH2OH containing system, the oxygen atom of hydroxyl group forms hydrogen bond with H2 atom (the hydrogen atom between two nitrogen atoms of five-membered ring) of BMI+ ion.The hydrogen bond is also formed between the hydrogen atom of hydroxyl group and fluorine atom of PF6－ ion. These interactions are stronger than those in ethanol containing system. The result is consistent with the observed downfield tendency of H2 chemical shift from nuclear magnectic resonance. Similar result is also obtained for the chemical shift of fluorine atom of PF6－ ion.
The fraction of free cation and anion increases with the diluent content, whose value is relatively large for CF3CH2OH containing system.
The number of coordinating PF6－ ions around BMI+ ion drecreases with the addititon of diluent. By contrast, the number of coordinating diluent molecules around BMI+ increases. The substitution effect is most pronounced as CF3CH2OH is added, due to it’s strong hydrogen bond ing ability with H2 atom of BMI+ ion.
Based on this work, the surroundings around the BMI+ ion is now clear, which is believed to be helpful for the microscopic explanation of experimental observations.
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校內：2014-02-09公開校外：2019-02-09公開