In order to vary the distance of positive and negative charge centers,
Δr, dicarboxylic acids were titrated with KOCH
3 and R
4NOH (R=CH
3, C
2H
5,
n-C
4H
9), as well as with LiOCH
3 and NaOCH
3. With tetramethylammonium hydroxide (TMAH), D
c value of numerous acids was obtained but less with tetraethylammonium hydroxide (TEAR), and not at all with tetrabutylammonium hydroxide (TBAH). As shown in Table I, values of D
c obtained with R
4NOH are much smaller than those obtained with alkali. It is suggested from the data shown by equations (1) and (2), and in Table II, that the values of
Δr TMAH and TEAH should be markedly large or small, and the values calculated from equation (3), based on the data in Table III, are 0.76 and 0.62 Å, respectively, being very small. This seems reasonable from the fact that, when titrated with two kinds of bases with different
Δr, values of D
c found were in good agreement with the values calculated from equation (4) and Fig. 2. The reason for this seems to be the displacement of charge center of R
4N
+, or a large overall dissociation constants of R
4N salts, rather than the solvation of alkali ions (Table V).
For the estimation of r,
Δr values of 2.35, 2.73, and 0.76 should respectively be adopted for NaOCH
3, KOCH
3 and TMAH, TMAH is especially useful since its salts are all soluble.
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