• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1418-1420
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• 1999

Kinetics and mechanism of the aminolysis of Z-thiophenyl acetates with X-benzylamines are investigated in acetonitrile at 45.0 ℃. The magnitudes of Bronsted coefficients β$_x$ (=1.3~-1.6) and β$_z$ (= -2.1~-2.4) are all large and cross-interaction constant ρxz is relatively large and positive (0.90). These trends are consistent with the rate-limiting breakdown of a tetrahedral intermediate, $T^±$. The proposed mechanism is also supported by adherence of the rate data to the reactivity-selectivity principle (RSP). The kinetic isotope effects, $k_H/k_D$, are greater than unity (1.3-1.4) suggesting a possibility of hydrogen-bonded four-centered transition state. The activation parameters, ΔH$^≠$ and ΔS$^≠$, are consistent with this transition-state structure.

• Bulletin of the Korean Chemical Society
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• 제13권6호
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• pp.642-647
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• 1992

Second-order rate constants have been measured spectrophotometrically for the reactions of substituted phenyl acetates with butane-2,3-dione monoximate and p-chlorophenoxide anions in MeCN-H$_2$O mixtures of varying compositions. The reaction rate, unexpectedly, decreased remarkably upon initial additions of MeCN to H$_2$O up to 30-40 mole ${\%}$ MeCN, and followed by a gradual increase upon further additions of MeCN. The change in solvent composition also influenced the magnitude of the ${\alpha}$-effect, i.e., the ${\alpha}$-effect increased as the mole ${\%}$ MeCN increased. The solvent dependent ${\alpha}$-effect for the present system appears to indicate that the differential solvation between the ${\alpha}$-effect nucleophile and the corresponding normal nucleophile is not solely responsible but the difference in the transition-state stabilization is also responsible for the ${\alpha}$ -effect in organic solvent-rich region.

• Bulletin of the Korean Chemical Society
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• 제29권9호
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• pp.1835-1838
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• 2008

• Bulletin of the Korean Chemical Society
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• 제11권4호
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• pp.262-265
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• 1990

• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.349-350
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• 2001

• 한국식품과학회지
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• 제22권6호
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• pp.659-667
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• 1990

옥수수전분을 무수초산과 아세틸화반응을 시켜 슬러리상태의 재래적인 방법과 예열처리에 의한 방법 및 extrusion 공정에 의하여 초산전분을 제조하여 이화학적 성질을 비교하였다. 재래적인 방법으로의 초산전분을 제조(CSA)할 경우 최고의 치환도를 갖는 반응 최적조건은 반응온도 $35^{\circ}C$와 반응 pH8.5이었다. Anhydrous glucose unit에 대하여 무수초산의 mole비를 0.03에서 0.2로 증가시킬 경우 최적조건에서의 치환도는 0.019에서 0.082로 증가한 반면 아세틸화반응 수율은 31.6%에서 20.5%로 감소되었다. 예열처리를 $65^{\circ}C$와 $90^{\circ}C$에서 처리하여 초산전분제조(PSA)시 치환도는 각각 0.027과 0.040 이었다. Extrusion 공정에 의한 초산전분제조(WESA)시 치환도는 0.02이었다. 초산전분의 호화개시온도와 호화 enthalpy는 치환도가 증가함에 따라 원료전분보다 낮아졌다. 모든 초산전분시료가 원료전분에 비하여 투명도가 증가되었고 색도에 있어서 명도는 감소되었고 황색도는 증가되었다. WESA 시료는 원료전분, CSA 및 PSA 시료에 비해 낮은 곁보기점도를 보였으며 뉴우톤성 유체에 접근하였다. 고유점도는 CSA와 WESA 시료가 원료전분보다 낮았으나 PSA 시료는 약간 큰 값을 보였다. 초산전분겔의 노화시간상수는 모든 초산전분시료가 원료전분보다 큰 상수값을 보였다.

• 생약학회지
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• 제26권3호
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• pp.227-238
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• 1995

Recent reports on biotransformation of monoterpene alchols, aldehydes, acetates and epoxides are summerized. The studies have focused on stereospecific reaction of the functional groups of exogenous foreign substrates by foreign plant cells and micro-organisms. An another important aspect of research is the development of the immobilization technique for cells or related enzymes.

• Bulletin of the Korean Chemical Society
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• 제25권2호
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• pp.328-330
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• 2004

• Bulletin of the Korean Chemical Society
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• 제26권3호
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• pp.481-484
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• 2005

• Bulletin of the Korean Chemical Society
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• 제26권6호
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• pp.1001-1004
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• 2005