Dimerization of Ion-Pairs from Sodium Diphenyl Phosphate in Acetone at Various Temperatures

Hojo, Masashi; Hasegawa, Hiroshi; Morimoto, Yasuhiro

doi:10.2116/analsci.12.521

Cited by 8 publications

(3 citation statements)

References 13 publications

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“…Vapor-phase osmometric and NMR studies have shown that LiCl is aggregated in THF. Stronger quadrupole formation with lower temperature has been reported for sodium diphenyl phosphate (Na + (PhO) 2 PO 2 - ) in acetone 1 Quadrupole from LiCl in THF 1 Formation Constants K 1 , K 2 = K 3 , and K 41 in THF at 25.0 °C K 1 K 2 K 41 ( K 2 / K 1 )10 3 × Δ C a rel.

…”

Section: Resultsmentioning

confidence: 93%

“…Stronger quadrupole formation with lower temperature has been reported for sodium diphenyl phosphate (Na + (PhO) 2 PO 2 -) in acetone. 21 Figure 2 shows the equilibrium concentrations of the various species related to the salt concentrations (C s ) of LiPic in THF at 25°C. With increasing salt concentration, the equiribrium concentration of simple ions decreases, while the concentration of the triple ions increases, the concentration of the ion pair being the predominant species over the whole C s range.…”

Section: Resultsmentioning

confidence: 99%

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Relationship between Triple Ion Formation Constants and the Salt Concentration of the Minimum in the Conductometric Curves in Low-Permittivity Solvents

Chen

Hojo

1997

J. Phys. Chem. B

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Conductivities of a number of uni-univalent salts, including tetrabutylammonium and lithium nitrophenolates, were measured at 25.0 °C in low-permittivity solvents such as tetrahydrofuran (THF, εr = 7.58), 1,2-dimethoxyethane (DME, 7.2), chloroform (4.8), and ethyl acetate (6.0). Minima in the conductometric curves (Λ−C 1/2) were observed for concentrations which were dependent upon both the salt and the solvent, C min = 1.73 × 10-4 mol dm-3 for 2,4-(NO2)2C10H5OLi (lithium 2,4-dinitro-1-naphtholate) in THF and 2.56 × 10-2 mol dm-3 for LiPic (lithium picrate) in DME. The observed molar conductivities including C min could be completely explained by the formation of ion pairs (M+ + X- ⇌ MX, K 1), “symmetrical” triple ions (2M+ + X- ⇌ M2X-, K 2; M+ + 2X- ⇌ MX2 -, K 3; K 2 = K 3), and (in some cases) additional formation of quadrupoles (2MX ⇌ M2X2, K 41). A linear relationship (the slope of −1) between the triple ion formation constants (log(K 2/K 1)) and the salt concentrations at the minimum (log C min) was given for all the salts in the various solvents, except for some systems in which a distinct formation of quadrupole takes place, e.g., LiNO3 in DME (K 1 = 3.16 × 1010, K 2 = 4.5 × 1013, and K 41 = 35). The formation of triple ions might be attributed to the ion sizes in solutions in which Coulombic interactions were the only main forces between ions (R4N+···X-). However, coordination (or covalent) bonding forces as well as Coulombic forces had to be considered for the lithium salts except for LiClO4 and LiBF4). Gutmann's donor and acceptor numbers of solvents (and not the permittivity) accounted for the larger difference of C min of lithium salts in THF and DME. In mixed solvents of THF and 2-ethyl-1-hexanol (εr = 7.58), the C min values of LiNO3 and 2,4-(NO2)2C10H5OLi increased with increasing contents of the hexanol, whereas the C min values of LiClO4 and Bu4NX (X- = NO3 -, 2,4-(NO2)2C10H5O-, and ClO4 -) remained constant for 0−30 vol % hexanol added to THF. The positive shifts in C min were explained quantitatively by the decrease in triple ion formation constants and/or by an increase in the quadrupole formation constants.

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…”

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Relationship between Triple Ion Formation Constants and the Salt Concentration of the Minimum in the Conductometric Curves in Low-Permittivity Solvents

Chen

Hojo

1997

J. Phys. Chem. B

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“…On the other hand, trifluoromethanesulfonic acid in benzonitrile gave a monotonical Λ-C 27 We have determined, by means of conductometry, the dimer formation constants of not only acids in DMF 4 , but also salts, CF 3 COOLi in propylene carbonate 18 and sodium diphenyl phosphate (Na + (PhO) 2 PO 2 -) in acetone. 26 …”

Section: Methodsmentioning

confidence: 99%

Appearance of Maxima on Conductometric Titration Curves of Sulfonic Acids and the Evidence of Strong Homoconjugation Reactions in Benzonitrile

Hojo

Chen

1999

ANAL. SCI.

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The conductometric titrations of acids with bases usually give decreasing or increasing straight lines from the beginning to the equivalence point in protic solvents. However, in aprotic solvents, such as acetone 1 and acetonitrile 2 , maxima at the half equivalence point on titration curves have been observed for carboxylic acids with amine bases. The cause of the maxima at the half equivalence point has been attributed to homoconjugation reactions 2 between an acid (HA) and the conjugate base anion (A -) on the neutralization: B+2HA BH + ... H 2 A -. In a poorly solvating solvent, nitrobenzene, the maxima could be observed even at the one-third, and not at the half equivalence point, suggesting the formation of an A -(HA) 2 -type homoconjugate species. 3 We have reported maxima on conductometric titration curves of phosphoric, phosphonic, and related organophosphorus acids with triethylamine in DMF. 4 The stability of the homoconjugated species was found to depend much upon the number of OH groups involved homoconjugation reactions, e.g., not (PhO) 2 PO(OH) but PhOPO(OH) 2 gave a maximum in DMF, regardless of the acidities of the acids.Gunduz et al. 5 stressed an important role of the base strength of a conjugate anion upon the appearance of maxima in conductometric titrations of substitutedacetic and benzoic acids. In acetonitrile, the equilibrium constants of the homoconjugation reactions of acetate and benzoate ions with two acid moleclues (A -+2HA A -(HA) 2 , K homo ) have been determined to be 5.7×10 7 and ca. 1×10 7 , respectively. 6 Some phenols, especially 3,5-dinitrophenol etc.1,7 can form the homoconjugate species in aprotic solvents. The homoconjugation reaction or the appearance of a maximum on conductometric curve of sulfuric acid (SO 2 (OH) 2 ) has been observed in acetonitrile 2,8 and acetone. 9 However, maxima on conductometric curves for sulfonic acids (RSO 2 (OH)) have not been reported so far, even though fairly large homoconjugation constants of sulfonic acids were obtained in acetonitrile. 10 An sulfonic acid has only a single OH group, while sulfuric acid has two OH groups in the molecule. Therefore, the stability of the homoconjugated species from an sulfonic acid must have been too small to give a maximum on the titration curve; this point encouraged us to perform the present study.Sulfonic acids are rather strong acids (e.g., pK a =0.7 for benzenesulfonic acid) 11 in aqueous solution, however, the acidities of the acids are extremely weakened in aporic solvents. 10,12 The dissociation and homoconjugation constants of methanesulfonic and related acids have been determined in propylene carbonate, and compared with those in acetonitrile. 13 We have reported 14 on the formation constants of "triple ions" of trialkylammonium sulfonates and nitrate through hydrogen bonding forces as well as Coulombic forces in benzonitrile. Judging from the 1:1 association and "triple ion" formation constants of R 3 NH + A -in benzonitrile, the basicity of the conjugate anions were found to increase as follo...

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Ligand Exchange Processes on Solvated Lithium Cations: Complexation by Cryptands in Acetone as Solvent

et al. 2007

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Dimerization of Ion-Pairs from Sodium Diphenyl Phosphate in Acetone at Various Temperatures

Cited by 8 publications

References 13 publications

Relationship between Triple Ion Formation Constants and the Salt Concentration of the Minimum in the Conductometric Curves in Low-Permittivity Solvents

Relationship between Triple Ion Formation Constants and the Salt Concentration of the Minimum in the Conductometric Curves in Low-Permittivity Solvents

Appearance of Maxima on Conductometric Titration Curves of Sulfonic Acids and the Evidence of Strong Homoconjugation Reactions in Benzonitrile

Ligand Exchange Processes on Solvated Lithium Cations: Complexation by Cryptands in Acetone as Solvent

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