| 研究生: |
黃瀕媚 Huang, Pin-Mei |
|---|---|
| 論文名稱: |
利用鹼催化環合形成5-腈尿嘧啶的反應:動力學以及反應機制之研究 General-base catalyzed ring-closure reactions to 5-yanouracils:kinetic and mechanistic studies |
| 指導教授: |
宋光生
Sung, Kuangsen |
| 學位類別: |
碩士 Master |
| 系所名稱: |
理學院 - 化學系 Department of Chemistry |
| 論文出版年: | 2006 |
| 畢業學年度: | 94 |
| 語文別: | 中文 |
| 論文頁數: | 55 |
| 中文關鍵詞: | Brønsted圖 、動力學研究 、5-腈尿嘧啶 、環合 、反應機制研究 、同位素效應 |
| 外文關鍵詞: | Brønsted plot, isotope effect, kinetic studies, mechanistic studies, ring closure, 5-cyanouracil |
| 相關次數: | 點閱:66 下載:1 |
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Z-ethyl[2-cyano-3-(substituted-amino)acry-loyl] carbamate, Z-3a~c的環合反應是一個general-base catalysis的反應。我們利用動力學實驗方法得知此反應的一級動力同位素效應值 kH/kD = 1.40;並從實驗結果得知Brønsted β value為0.174;同時藉由立體效應影響的實驗結果發現氮上取代基立體障礙越大、或為拉電子取代基皆會使環合反應速率變慢。
我們綜合kinetic isotope effect、 Brønsted plot和 N-substituent effect的實驗結果,進一步推導出Z-3a~c的鹼催化環合反應的反應機制,發現反應速率決定步驟包含proton transfer並同時發生分子內親核加成,隨後才脫去ethoxide。
The ring-closure reactions of Z-ethyl[2-cyano-3- (substituted-amino)acry-loyl] carbamate, Z-3a~c, are general-base catalysis. Primary kinetic isotope effect of kH/kD = 1.40, the Brønsted β value of 0.174, and reduction of the NEt3-catalyzed ring-closure rates by bulky or electron-withdrawing N-substituents confirm that the mechanism for the general-base catalyzed ring-closure reactions of Z-3a~c involves the rate-determining simultaneous proton transfer and intramolecular nucleophilic addition, followed by elimination of ethoxide.
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