YOSHIDA Masafumi Kumamoto Univ., Faculty of General Education, Natural Sci. Dept., Assoc. Prof., 教養部, 助教授 (10040114)
TANAKA Akira Kumamoto Univ., Dept. of Chem., Instructor, 理学部, 助手 (50163499)
SANEMASA Isao Kumamoto Univ., Dept. of Chem., Prof., 理学部, 教授 (60040119)
Cyclodextrins (CyDs, cyclic oligosaccharides consisting of six, seven, or eight glucopyranose units, called alpha, beta, or gamma, respectively, with a central cavity of the corresponding size) have attracted interests of many workers due to their unique properties. It is well-established that CyDs (hosts) form inclusion complexes with a variety of molecular species (guests) in aqueous medium. In this host-guest association, the size (and shape) and hydrophobicity of a guest moecule play an important role.
We have recently found that beta-CyD is easily precipitated from aqueous solution upon introducing cyclohexane vapor into the solution. There is a possibility that, When hydrophobic solutes are present in the aqueous solution, these solutes may be coprecipitated with CyD. The present research is concerned with this possibility using 8 kinds of aromatic hydrocarbons with a view to develop a new method to concentrate hydrophobic solutes from water to the CyD solid phase.
Aqueous sample s
olutions were prepared by adding each aromatic hydrocarbon of known concentration to 3.0X10^<-3> mol dm^<-3> beta-CyD aqueous solution. Then, cyclohexene vapor was introduced into the sample solution and circulated in a closed system for two minutes. The aqueous phase becomes turbid owing to CyD precipitation just after introduction of cyclohexene vapor. The CyD solid phase was collected and the recovery of sample hydrocarbon was determined. It was found that anthracene, Phenanthrene, fluorene, fluoranthene, and pyrene are coprecipitated with CyD almost quantitatively, but this is not the case for highly volatile solutes such as benzene, biphenyl, and naphthalene. The mechanism of the present coprecipitation of aromatic hydrocarbons with CyD was discussed based on the data of 1 : 1 association constant of each host-guest system.
The present research is also concerned with the determination of association constant of a series of aromatic hydrocarbons with alpha-, beta-, and gamma-CyDs.
A new technique was also proposed in this research. That is, hydrophobic solutes such as Fe (III) -8-hydroxyquinolate, Ni (II) -dimethylglyoximate, and some non-volatile aromatic hydrocarbons can be extracted onto a polytetrafluoroethylene film surface. Less