EFFECTIVE NEUTRAL DEAGGREGATORS

Hydrolysis of the aggregated p-nitrophenyl hexadecanoate (C16-Ag) can be appreciably or greatly accelerated by some neutral molecules, hereafter called ''deaggregators'' or deAgr's, e.g., n-octyl-alpha-D-glucopyranoside (alpha-G-8), n-dodecyl-alpha-D-glucopyranoside (alpha-G-12), n-dodecyl-beta-D-glucopyranoside (beta-G-12), 13,17-dioxa-15-nonacosanyl-beta-maltoside (M-2-12), and 17,21-dioxa-19-heptatriacontanyl-beta-maltoside (M-2-16), in the 40:60 (v/v) (phi = 0.40) and 45:55 (v/v) (phi = 0.45) dioxane-H2O aquiorgano solvent. Experimental data show that the rate enhancement of the C16-Ag is most likely brought about by processes depicted by our simplified ''deaggregation'' scheme (Scheme 1), i.e., the deAgr molecules first break into the C16-Ag, then ''grab'' one (or more) C16 molecule(s) and carry it (them) into the bulk of solvent in which the C16 molecule is released in its monomeric form. Two double-chained deAgr's (M-2-12 and M-2-16) that incorporate hydrophilicity and lipophilicity in an effective and balanced manner possess deaggregating abilities orders of magnitude greater than those of the typical ionic surfactants. The above-mentioned scheme is fully supported by fluorescence spectroscopy with 1-(alpha-naphthyl)-3-oxapentadecane (Np-12) as the fluorescence probe.