イオン会合抽出における陽,陰イオンの相対的抽出性と抽出定数の推定

水-クロロホルム系でのイオン会合抽出におけるイオンの抽出性の相対的尺度として,陽イオンに対しC値,陰イオンに対しA値を割り当てた.これらの値の算出の際の基準にはアルキル鎖及び水素原子を全く持たない仮想的な陽イオン[-〓N-(+)]をとった.C値,A値と抽出定数(logK(ex))の関係は,logK(ex)=C+Aで表される.陽イオンとして14種の第四級アンモニウムイオン,テトラフェニルホスホニウム(アルソニウム)イオン,5種のアゾ系染料陽イオン,7種のトリフェニルメタン系染料陽イオン及びメチレンブルーのC値を決めた.又π値(置換基の寄与)を用いるC値の計算方法についても考察した.C値を用い,無機,有機陰イオンのA値も決定した.得られたC値及びA値を用いて約150種のイオン会合体の抽出定数を推定し,既報の実測値との比較をしたところ,±0.3log単位程度の誤差であった.又著者以外により報告されている抽出定数との一致も良好であった.

Extraction constant, K(ex), for the chloroform extraction of ion associates from aqueous solution was divided into two parameters, C and A, assigned to the cation and the anion, respectively: logK(ex)=C+A. In estimating the values of C or A for various ions, a hypothetical cation, -N_??_-(+) (long-chain alkyltrimethylammonium type), with no alkyl groups nor hydrogen atoms was chosen as a reference ion for which C=0. C value for long-chain alkyltrimethylammonium cations can be calculated from C=0.59n, where n is the number of carbons and 0.59 is the value of π(CH(2)), contribution constant of methylene group to extraction constant. C values for other alkylammonium ions were determined experimentally and compared with those calculated on the assumption of additivity of contribution constants of functional groups. C values for other cationic groups were as follows: -1.20 for -N_??_-(+) (symmetrical tetraalkylammonium type), -0.56 for >-NH(3)(+) 0.40 for NH(2)(+), 1.29 for _??_ NH(+), 4.72 for -_??_NH(+), 7.53 for -(+)N_??_-N=N-_??_N(C(2)H(5))(2), and 10.74 for C(C(6)H(4)-)(3)(+), respectively. By using these C values, A values for inorganic and organic anions were determined. A values for inorganic anions were as follows: -11.06 for F(-), -9.07 for OH(-), -8.11 for NO(2)(-), -8.08 for Cl(-), -7.05 for NO(3)(-), -6.89 for Br(-), -5.80 for BF(4)(-), -5.32 for I(-), -5.17 for SCN(-), -5.03 for ClO(4)(-), and -4.45 for ReO(4)(-), respectively. A values for anionic groups were as follows: -9.08 for -SO(3)(-), -10.73 for -COO(-), and -7.38 for -OSO(3)(-), respectively. By using the values of C and A, the extraction constants (logK(ex)) for ion associate (C(+)·A(-)) were estimated and compared with those obtained experimentally. The differences between them were smaller than ±0.3 log unit.