Acetone— 572 association constants

In contrast, reaction of ligand 72 with 4,4 -biphenyldiboronic acid has been successful and diboronate 73 is obtained in yields of 33%. This complex acts as a receptor for the paraquat dication forming a 1 1 complex with an association constant of 320 in acetone. The intermolecular forces responsible for the complexation are ion-dipole stabilization between the dative N B dipoles and the two cationic centers in paraquat, attractive tz-tz interactions between... 

The determination of the association constant K values can be done either graphically or numerically (Kertes and Gutmann, 1976). The K values can be used to estimate thermodynamic quantities such as AG°, AH° and AS0. The interactions of polar substances, such as methanol, ethanol and acetone, with Aerosol OT in toluene systems were examined (Kon-no, 1993). The negative AG° value was found in the decreased order methanol > ethanol > acetone and the contribution to AG° was AH° > TAS°. This result indicates that the solubilization of three solutes with Aerosol OT micelle is an enthalpy driven process. 

The anion templated syntheses by Beer afforded receptors 60-62 by reacting the chloride salt of the starting pyridinium precursor with an appropriately chosen 1,3-diamidobenzene derivative. Based on 1H NMR spectroscopic titrations carried out in acetone-d6, the structure Cl 60 was found to form with a 1 1 stoichiometry and with an association constant of 2400 M-1. 

Table 2. Association constants (K.assoc) for 1 1 complexes between diquat and dibenzocrown ethers 4 in acetone at 25.5 °Ca...

This equation accounts for experimental association constant values higher than theoretical ones because KA > Ki. Moreover, we may deduce that when cations are equal, KA is smaller for smaller anions, which means that they have a greater charge density and thus are more basic, since K2 is lower for them. On the contrary, KA values decreasing with an increase in the size of the anion have been observed in aprotic solvents like TMS (II), acetone (41), nitrobenzene (42), nitromethane (43), acetonitrile (44), and 1,1,3,3-tetramethylurea (45). This order can be understood if one considers that in this class of solvents the anions are scarcely solvated so that association is affected mainly by the strength of cation-anion interaction, which, with the cations being equal, increases with an increase in the anion charge density. 

Beer and co-workers have reported the anion-binding abiUty of a number of indolocarbazoles sensors (54a-c) [72]. The highest association constants were obtained with receptor 54c presumably due to the presence of the electron-withdrawing bromide groups increasing the acidity of the NH groups. UV-Vis spectroscopic titrations in acetone at 25 C revealed that... 

Evans, Zawoyski and Kay analysed data for R4N salts in acetone (AC) " with the Fuoss-Onsager equation. They found Ka decreases with cation size, and for the anions, association decreases in the order Bu4NBr(i = 264) > I-(143) NOg > CIO4 (80) > Pic-(17). This agrees with data for methylethylketone. The fact that association of Bu4NC104 in AC, benzonitrile, and methylethyl-ketone corresponds to = 4.85 A for the three solvents, indicates formation of contact ion pairs. Tetraalkylammonium halides in dimethyl-formamide (DMF) have small association constants when the data are evaluated with Shedlovsky s eqn. 5.4.10. When the data for Me4NPic in is assessed with Fuoss and Hsia s eqn. 5.2.31, a is 6.0 A. 

Rate laws, rate constants, and activation parameters have been established for exchange of acetylacetone (acacH) with [V(acac)3] in several organic solvents, including acetylacetone itself. The mechanism is thought to be associative, but to involve intermediates containing unidentate acetyl-acetonate. Rate constants for exchange in methanol, ethanol, chloroform, acetonitrile, and dimethyl sulfoxide cover a range of 10 rates appear to... 

Furthermore, m-cresol and m-halogenated phenols have been polymerized in aqueous buffer solution only in the presence of 2,6-di-0-methyl-[)-cyclodextrin [90]. In the absence of cyclodextrin, only insoluble materials in very low yields were obtained under aqueous conditions from these phenols [81]. The structure of the host-guest complexes between cyclodextrin and the phenols was characterized by 2D NMR [48,90] and the association constants of the cyclodextrin complexes were determined by the Benesi-Hildebrand method. Firrthermore, 3-fluorophenol, 3-chlorophenol, and 3-bromophenol were successfully polymerized in various aqueous organic solvents such as methanol, acetone, or isopropanol [115]. 

Singh, P. P. Malik, R. Maken, S. Acree Jr., W. E. Zvaigzne, A. L Thermochemical investigations of associated solutions. 12. Mole fraction versus volume fraction based association constants for predicting excess molar enthalpies of acetone-bromoform-alkane mixtures Thermochim. Acta 1990,165,113-127... 

An association constant K = 3100 M for the 1 1 complex between 25 and trimethylanilinium chloride in water at pH 7.3 and 25°C was established by the computer assisted non linear least-square analysis of H NMR titration experiments [38]. This value is lower than = 5390 M found in the same conditions for the inclusion of the guest 26 into the cavity of the flexible host 24 [37]. On the other hand the association constant of acetone with the preorganized host molecule 25 was found... 

Fig. 2 Bis- and tris(iodoperfluoroarene) anion receptors 2a-3c. Association constants with Bu4isrCP (acetone, 295 K) are listed...

Table 5 Association constants AT, for interactirais between Bu4N X and tridentate halogen bond draior 3c (acetone, 295 K)...

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