Abstract
Two series of N-[2- [ω-methyl oligo (oxyethylene)] decyl ]monoaza crown ethers (2 a-c and 2 d-f) were prepared from N- (2-hydroxydecyl) monoaza crown ethers (1 a : -15-crown-5 and 1 b : -18-crown-6) and ω-methyl oligo (oxyethylene) tosylates (Scheme-1). The cloud point, complexing stability constant (log K1') with alkali metal cations (Na+ and K+) in methanol and phase-transfer catalysis (PTC) were determined for the products and compared with those of reference compounds.
The crown ethers with oligo (oxyethylene) chains (2) generally showed higher cloud points and greater log K1' than those of the corresponding N-decyl monoaza crown ethers (3). The cloud points of (2) in both series and log K1' (K+) of (2) in 15-membered series increased with the number of oxyethylene units in the side chain. A plot of log K1' (Na+ and K+) vs. the total number of oxygen atoms in a molecule of the crown compounds showed a clear peak at six oxygen atoms for each series except for log K1' (K+) of the 15-membered series.
The enhanced cation-complexing ability of (2) reflects the high efficiency of PTC with (2) which was superior to that of any of the reference compounds, (1), (3) or (4). The order of log K1' showed close correlation with the PTC efficiency in each series.
