Large extractability of aluminium(III) with 2-methyl-8-quinolinoi derivatives in the presence of 3,5-dichlorophenol

The extraction of aluminium(III) with 2-methyl-8-quinolinol derivatives (HA ), such as 2-methyl-8-quinolino1 (HMQ), 2-methyl-5-methoxymethyl-8-quinolin ol (HMO(1)Q), and 2-methyl-5-octyloxymethyl-8-quinolinol (HMO(8)Q), from a weakly acidic solution into heptane was studied in both the absence and pre sence of 3,5-dichlorophenol (Hdcp) as the synergist. In the absence of Hdcp , aluminium(III) was not extracted with HMQ and HMO(1)Q due to a steric hin drance of the methyl group at the 2-position at all, but was slightly extra cted with HMO(8)Q. The unusual extraction behavior of aluminium(III) with H MO(8)Q should be ascribed to the formation of a hydrophobic aluminium(III)- HMO(8)Q complex. Aluminium(III) was quantitatively extracted with HA into h eptane upon the addition of Hdcp. The large synergism of Hdcp was ascribed to the formation of an inner-sphere complex, Al(dcp)(A)(2), in an aqueous p hase and an outer-sphere complex, Al(dcp)(A)(2). Hdcp, in the organic phase . The compositions of extracted aluminium(III)-HA-Hdcp were assigned to be Al(dcp)(A)(2). Hdcp. The synergistic extraction constants (K-ex,K-s = [Al(d cp)(A)(2). Hdcp](org)[H+](3)[Al3+](-1)[HA](org)(-2) [Hdcp](org)(-2)) for Al (dcp)(A)(2). Hdcp are 10(-5.75+/-0.12) (HMQ), 10(-4.74+/-0.05) (HMO(1)Q), a nd 10(-3.98+/-0.19) (HMO(8)Q), respectively, at I = 0.1 M (H, Na) ClO4(1 M = 1 mol dm(-3)) and 25 degrees C.