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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 32, Number 1
JKCSEZ 32(1)
February 20, 1988 

 
Title
Formation Constants of 18-Crown-6 Complexes with Substituted Potassium Phenoxides

치환 Potassium phenoxide와 이루는 18-Crown-6 Complex의 형성상수
Author
Soo-Dong Yoh, Soon-Kyoo Kim, In-Sook Han, Jong Hwan Park

여수동, 김순규, 한인숙, 박종환
Keywords
Abstract
파라치환된 포타슘 페녹사이드류와 18-crown-6가 이루는 1 : 1 착물 형성상수를 전기 전도도법으로 35℃에서 측정하여 용매와 치환기의 변화에 따른 효과를 측정하였다. 18-crown-6와 K+의 착물 형성상수는 CH3OH(DN=19.0) > DMF(26.6) > DMSO(29.8)의 순으로 감소되었다. 이는 전자주게 수가 클수록 K+과 용매와의 상호작용이 커지므로 크라운 에테르와의 착물형성과의 서로 경쟁관계가 되어 Kf값이 작아진다고 추정된다. 포타슘 페녹사이드의 치환기가 p-NO2 > H > p-CH3 > p-OCH3의 순으로 Kf값이 감소하는 경향을 나타내었다. 이는 전자를 당기는 기는 페녹사이드 음이온이 비편재화되어 안정해지므로 전자를 미는 기에 비해서 K+를 쉽게 내어 놓을 수 있어 18-crown-6와의 착물 형성이 용이하기 때문이라고 생각된다.

Recently, the formation of the complexes between macrocyclic polyethers and alkali metal salts have been determined by several methods. It has been suggested that the specificity of the complexation be due to the nature of the surrounding solvent molecules. The formation constant values (Kf) of K+ are shown to be the largest among the other alkali metal cations because the ionic diameter of K+ is approximately the same with the hole size of 18-crown-6. In this study the formation constants of the 1 : 1 complexes of 18-crown-6 with potassium p-substituted phenoxide are calculated by the conductance measurement in organic solvents. As a result, the Kf value series among organic solvents are given in the order of CH3OH > DMF > DMSO. It seems that the donor number of the solvent is a main factor in the formation of the complex between K+ metal ion and 18-crown-6 molecules. At the same time, the formation constants increase with increasing the electron-withdrawing power of substituents because the phenoxide ion is stabilized by the charge dispersion.

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