ASSOCIATION OF C5-C9 NORMAL ALKANES WITH CYCLODEXTRINS IN AQUEOUS-MEDIUM

The complex formation of cyclodextrin (CyD, host) with C5 to C9 normal alkanes (guests) has been studied in aqueous medium at 25 °C by making use of the volatilization rate of alkane molecules from aqueous into gaseous phase. In the excess of the host, β- and γ-CyDs form 1:1 complexes, while α-CyD forms 1:1 and 2:1 (host : guest) complexes. With an increase in the chain length of alkane, association constants for three CyDs increased; in the case of a-CyD, the 1:1 association constant for C 9 was identical to that for C8, while the 2:1 association constant continued to increase. The cavity size of CyD, the alkane chain length, and hydrophobicity and surface area of alkane molecules were taken into account to discuss the host-guest inclusion mechanism. © 1990 The Chemical Society of Japan.