View : 651 Download: 0

Full metadata record

DC Field Value Language
dc.description.abstractIn this thesis, there are three sections of kinetic studies for reactions of 1-(Y-substituted-phenoxy)-2,4-dinitrobenzenes with alkali-metal ethoxides (1) and cyclic secondary amins (2), and aminolysis of 4-nitrophenyl 3,5-dinitrobenzoate (3). Each summary is shown below. (1) The first observation of alkali-metal ion catalysis and inhibition in SNAr reactions is reported. Plot of kobsd vs [alkali-metal ethoxide] exhibits downward curvature for the reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with EtOLi, EtONa and EtOK, but upward curvature for the corresponding reaction with EtOK in the presence of 18-crown-6-ether (18C6). Dissection of kobsd into the second-order rate constants for the reactions with the dissociated EtO- and the ion-paired EtOM (i.e., kEtO- and kEtOM, respectively) has revealed that the reactivity increases in the order EtOLi < EtONa < EtOK < EtO- < EtOK/18C6. This indicates that the reaction is inhibited by Li+, Na+ and K+ ions but is catalyzed by 18C6-K+ ion. The reactions of 1-(Y-substituted-phenoxy)-2,4-dinitrobenzenes (1a-1h) have been proposed to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs after the rate-determining step based on the kinetic result that σo constants exhibit a much better Hammett correlation than σ- constants. Alkali-metal ion catalysis or inhibition has been discussed in terms of differential stabilization of ground-state and transition-state complexes via a qualitative energy profile. A π-complexed transition-state structure is proposed to account for the kinetic results. (2) A kinetic study is reported for SNAr reactions of 1-(Y-substituted-phenoxy)-2.4-dinitrobenzenes (1a-1h) with amines in MeCN. The plots of pseudo-first-order rate constant versus amine concentration curve upward, indicating that the reactions are catalyzed by a second amine molecule. The Brønsted-type plots for the reaction of 1-(4-nitrophenyl)-2,4-dinitrobenzene (1a) with a series of secondary amines are linear with βnuc = 1.10 and 0.85 for the uncatalyzed and catalyzed reactions, respectively, while the Yukawa-Tsuno plots for the reactions of 1a-1h with piperidine result in excellent linear correlations with ρY = 1.85 and r = 0.27 for the uncatalyzed reaction and ρY = 0.73 and r = 0.23 for the catalyzed reaction. The catalytic effect exerted by a second amine molecule decreases with increasing amine basicity or electron-withdrawing ability of the substituent Y in the leaving group. Activation parameters calculated from the rate constants measured at five different temperatures for the catalyzed reaction of 1a with piperidine are ΔH‡ = 0.38 kcal/mol and ΔS‡ = -55.4 cal/mol K. The catalyzed reaction from a Meisenheimer complex (MC±) is proposed to proceed through a concerted mechanism with a cyclic intermediate rather than via a stepwise pathway with an anionic intermediate (MC-, a deprotonated form of MC±). (3) Kinetic study for reactions of 4-nitrophenyl 3,5-dinitrobenzoate (2) with a series of cyclic secondary amines in acetonitrile is reported. Plots of pseudo-first-order rate constant (kobsd) vs [amine] curve upward, while those of kobsd /[amine] vs [amine] exhibit excellent linear correlations with positive intercepts, indicating that reaction proceeds through both uncatalyzed and catalyzed routes. Brønsted-type plots for uncatalyzed and catalyzed reactions are linear with βnuc = 1.03 and 0.69, respectively. The ΔH‡ and ΔS‡ values measured for the catalytic reaction with morpholine are -0.80 kcal/mol and -61.7 cal/mol K, respectively. The negative ΔH‡ with a large negative ΔS‡ suggests that the reaction proceeds through a highly ordered transition-state (i.e., a six-member cyclic transition-state, which includes a second amine molecule that accepts a proton from the aminium moiety of zwitterionic-tetrahedral intermediate and simultaneously donates a proton to the aryloxyl oxygen of the nucleofuge with concomitant C-OAr bond scission). This proposal is consistent with the smaller βnuc value for the catalyzed reaction as compared to the uncatalyzed reaction. An inverse deuterium kinetic isotope effect (DKIE) value of 0.93 and a contrasting normal primary DKIE value of 3.23 for the uncatalyzed and catalyzed routes, respectively, also support the proposed cyclic TS.;본 논문은 1-(Y-substituted-phenoxy)-2,4-dinitrobenzenes(1a-1h)의 alkaline ethonolysis (1), aminolysis (2) 그리고 4-nitrophenyl 3,5-dinitrobenzoate(2)의 aminolysis (3) 를 다루었으며, 각 논문의 개요는 다음과 같다. (1) 무수 에탄올에서 1-(Y-subsituted-phenoxy)-2,4-dinitrobenzenes(1a-1h)와 EtOM의 SNAr 반응에 대한 반응속도 연구를 수행하여 알칼리 금속 이온의 촉매효과와 억제효과에 대해 관찰하였다. EtOLi, EtONa 그리고 EtOK의 반응에 대한 1a의 kobsd vs. [EtOM] 그래프들은 아래로 향하는 곡선을 보이는 반면 18C6가 존재하는 EtOK와의 반응에서는 위로 향하는 곡선이었다. kobsd를 해리된 EtO-와 이온쌍을 이룬 EtOK 의 반응에 대한 이차 속도 상수 kEtO-와 kEtOK로 나누었다. 그 결과 EtOM의 반응성은 kEtOLi < kEtNa < kEtOK < kEtO- < kEtOK/18C6 순서로 증가하였으며, 이는 Li+, Na+ 그리고 K+ 이온은 반응을 저해시키고 18C6가 존재하는 K+ 이온은 촉매 작용을 했다는 것을 의미한다. Hammett 그래프에서는 σ-상수보다 σo 상수와의 상관관계가 훨씬 좋으며 이는 1a-1h의 반응이 이탈기가 떨어져 나가는 단계가 속도결정단계인 stepwise mechanism으로 진행할 것이라고 결론 내릴 수 있었다. 알칼리 금속 이온의 촉매효과와 저해효과는 qualitative energy profile을 통해 ground-state와 transition-state가 차등적으로 안정화한다는 관점으로 설명하였다. π-complexed transition-state 구조는 반응속도 연구 결과를 토대로 제안하였다. (2) 1-(Y-subsituted-phenoxy)-2,4-dinitrobenzenes(1a-1h)와 일련의 고리형 2차 amine의 SNAr반응을 MeCN에서 수행하여 유사일차속도상수(kobsd)를 측정하였다. 실험 결과 kobsd vs. [amine] 그래프는 위로 휘는 곡선의 그래프로 나타났으며, 이는 또 하나의 amine 분자가 촉매작용을 한다는 것을 의미한다. 1a와 2차 amine들의 반응 결과 Brønsted-type 그래프들은 Kk2와 Kk3에 대해 각각 βnuc = 1.10와 0.85 인 직선으로 나타났으며, 1a-1h와 piperidine의 반응 결과 Yukawa-Tsuno 그래프는 Kk2의 경우 ρY = 1.85 와 r = 0.27 그리고 Kk2의 경우에는 ρY = 0.73 와 r = 0.23 을 가지는 완벽한 직선이었다. 또 다른 amine에 의한 촉매 효과는 amine의 염기성과 이탈기의 Y 치환기의 전자끌개능력이 커질수록 줄어든다. 1a와 piperidine의 반응속도를 서로 다른 다섯 개의 온도에서 측정하여 얻은 활성화 파라미터를 통해 ΔH‡ = 0.38 kcal/mol 와 ΔS‡ = -55.4cal/mol K. 를 계산할 수 있었다. Meisenheimer complex에서 촉매 반응은 고리형 전이상태를 형성하는 concerted mechanism인 것으로 제안하였다. (3) MeCN에서 고리형 2차 amine들과 4-nitrophenyl 3,5-dinitrobenzoate(2)의 친핵성 치환반응에 대한 반응속도론적 연구를 수행하였다. 유사일차속도상수(kobsd)를 [amine]와 상관지은 그래프(kobsd vs[amine])는 위로 휘어지는 곡선인 반면, kobsd /[amine] vs [amine] 그래프는 양의 절편을 가지는 직선을 얻었으며, 이는 본 반응이 uncatalyzed와catalyzed 경로를 통해 진행한다는 것을 의미한다. Brønsted-type 그래프에서는 Kk2와 Kk3에 대해 각각 βnuc = 1.03 그리고 0.69인 좋은 직선으로 나타났다. 활성화 파라미터를 통해morpholine과의 촉매 반응에서의 ΔH‡ = -0.80 kcal/mol와 ΔS‡ = -61.7 cal/mol K 값을 계산하였다. 큰 음의 ΔS‡ 값을 가지는 음의 ΔH‡ 값을 근거로 본 반응이 또 하나의 아민이 기여하는 6각형 고리형 구조를 통한 높은 transition-state를 거쳐 진행한다고 주장할 수 있다. 이 제안은 catalyzed 반응의 βnuc 값이 uncatalyzed의 값보다 현저히 작다는 사실과 일치한다. 또한 uncatalyzed 반응에서 나타난 역 중수소효과와 일반적인 중수소 효과가 나타난 catalyzed 반응은 제안한 고리형 전이상태 구조를 더 강하게 뒷받침한다.-
dc.description.tableofcontentsI. Introduction 1 II. Experimental 3 A. Synthesis of substrates and preparation of solutions 3 1. Substrates 3 2. Nucleophlies 3 3. Reaction Media 3 B. Kinectics 4 III. Results and Discussion 5 A. Alkaline ethanolysis of 1-(Y-substituted-phenoxy)-2,4-dinitrobenzens: alkali-metal ion catalysis and inhibition in SNAr displacement 5 1. Curvature of Rate Plots and Role of M+ Ions 7 2. Dissection of kobsd into kEtO- and kEtOM 10 3. Effect of Leaving-Group Substituents on Reactivity 11 4. Hammett Plots and Reaction Mechanism 16 5. TS Structure and Role of M+ Ions 19 6. GS and TS Stabilization by M+ Ions 20 B. SNAr reaction of 1-(Y-substituted-phenoxy)-2,4-dinitrobenzenes with cyclic secondary amines in acetonitrile 22 1. Effect of Amine Basicity on Reactivity and Reaction Mechanism 25 2. Effect of Leaving-Group Basicity on Reactivity and Reaction Mechanism 28 3. Deduction of Reaction Mechanism 35 4. Deduction of TS Structure from Activation Parameters 36 C. Aminolysis of 4-nitrophenyl 3,5-dinitrobenzoate in acetonitrile: evidence for a catalytic six-member cyclic transition state 47 1. Dissection of kobsd into Kk2 and Kk3 49 2. Brønsted-type Analysis of Kk2 and Kk3 53 3. Analysis of Activation Parameters 55 4. Deduction of Reaction Mechanism 62 5. Deuterium Kinetic Isotope Effect 63 IV. Couclusion 68 V. Reference 70 국문초록 75 List of publications 77-
dc.format.extent1050270 bytes-
dc.publisher이화여자대학교 대학원-
dc.titleKinetic Studies on SNAr Reactions of 1-(Y-Substituted-Phenoxy)-2,4-Dinitrobenzenes with Alkali-Metal Ethoxides and Cyclic Secondary Amines, and Aminolysis of 4-Nitrophenyl 3,5-Dinitrobenzoate-
dc.typeMaster's Thesis-
dc.format.pagex, 81 p.-
dc.identifier.major대학원 화학·나노과학과- 2-
Appears in Collections:
일반대학원 > 화학·나노과학과 > Theses_Master
Files in This Item:
There are no files associated with this item.
RIS (EndNote)
XLS (Excel)


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.