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이종팔,Ae Ri Bae,엄익환 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.6
A kinetic study is reported for nucleophilic substitution reactions of 4-pyridyl X-substituted benzoates 7a-e with a series of alicyclic secondary amines in H_2O. The Brønsted-type plot for the reactions of 4-pyridyl benzoate 7c is linear with β_(nuc) = 0.71. The corresponding reactions of 2-pyridyl benzoate 6, which is less reactive than 7c, resulted in also a linear Brønsted-type plot with β_(nuc) = 0.77. The fact that the more reactive 7c results in a smaller β_(nuc) value appears to be in accord with the reactivity-selectivity principle. The aminolysis of 7c has been suggested to proceed through a stepwise mechanism in which breakdown of the intermediate is the rate-determining step (RDS). The Hammett plot for the reactions of 7a-e with piperidine consists of two intersecting straight lines, i.e., ρX = 1.47 for substrates possessing an electron-donating group (EDG) and ρX =0.91 for those possessing an electron-withdrawing group (EWG). In contrast, the corresponding Yukawa-Tsuno plot exhibits excellent linear correlation with ρX = 0.79 and r = 0.56. Thus, it has been concluded that the nonlinear Hammett plot is not due to a change in the RDS but is caused by stabilization of the ground state of the substrates possessing an EDG through resonance interaction between the EDG and the C=O bond of the substrates.
이종팔,임귀택,이용희,구인선,류준하,Lee, Jong-Pal,Im, Gwi-Taek,Lee, Yong-Hui,Gu, In-Seon,Ryu, Jun-Ha 대한화학회 2002 대한화학회지 Vol.46 No.4
5-치환 2-Furaldehyde류의 양성자화 반응을 25$^{\circ}C$, 황산 수용액 속에서 분광광도법으로 조사하여 각 반응물질의 염기도 상수인 p$K_{BH+}$값을 과산도 (execess acidity)법으로 구하였다. 전자 주게 치환기를 가진 5-methyl-2-Furaldehyde의 염기도 상수는 전자 받게 치환기를 가진 5-nitro-2-Furaldehyde의 염기도 상수보다 크게 나타났으며 pK단위로 3.25정도 차이가 나는 것을 알수 있었다. 각 반응기질의 양성자화 반응으로부터 형성된 짝산의 용매화 정도를 나타내는 m값은 본 반응계와 유사한 반응물질인 acetophenone과 비슷한 크기로 나타남을 알 수 있었다. 2-Furaldehyde의 치환기 변화에 따른 염기고 상수의 변화 값인 -${\Delta}pK_{BH+}$과 m의 상관관계가 좋은 직선성을 보였다 The protonation equilibrium of 5-substituted 2-furaldehydes is investigated spectrophotometrically in aqueous sulfuric acid at $25^{\circ}C$ and the basicity constants(p$K_{BH+}$) of the substrates is calculated by means of the excess acidity method. The basicity constant of 5-metyl-2-furaldehyde having electron donating group is larger than that of 5- nitro-2-furaldehyde having electron withdrawing group. Difference between the basicity constants(p$K_{BH+}$) of these two compounds was about 3.25 pK unit. The m value which is the degree of solvation of the protonated substrate is similar to that of acetophenone having same protonation site. The dependence of p$K_{BH+}$ on m value shows good linear cor-relation.