Spectrophotometric, polarographic and conductometric evidence for triple ion formation from benzenesulfonate and diphenyl phosphate salts in protophobic aprotic solvents

Hojo, Masashi; Hasegawa, Hiroshi; Miyauchi, Yuhei; Moriyama, Hironori; Yoneda, Hitoshi; Arisawa, Souichirou

doi:10.1016/0013-4686(94)80003-0

Cited by 31 publications

(14 citation statements)

References 24 publications

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“…Since then, we have revealed that the Li + ion operates an unexpectedly strong coordination ability in protophobic aprotic solvents. 8,9 Our method was found to be very useful for examining complex formation between alkali metal ions and macrocyclic polyamines (cyclam, tetramethylcyclam) 10,11 as well as acyclic polyamines (ethylenediamine, trien, tetren). 12 The complex formation of cryptand [2.2] and its sulfur derivative (ATCO: 1,10-diaza-4,7,13,16-tetrathiacyclooctadecane) with alkali metal or alkaline earth metal ions in acetonitrile has been examined.…”

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Interaction between Monoaza-, Diaza-, or Polyazacrown Ethers and Alkali Metal Ions in Acetonitrile by Polarography

et al. 2000

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Crown-type compounds are of general relevance as synthetic model substances for studying physiological ion-transport processed in biological membranes, for investigating receptor and enzyme interactions as well as for the salt balance and for metabolic processes of living organisms. 1 The complexation between alkali metal ions and macrocyclic polyethers, polyamines or polyetheramines has been extensively studied by means of various methods in many solvent systems. 2,3 The fitness of the cavity size of a macrocyclic compound is an important factor for determining the stability of an alkali metal complex. 4 Solvent effects in the complexation of cryptand [2.2] (1,10-diaza-18-crown-6) with Li + have indicated that the stability of the complex varies inversely with the donicity of the solvent.5 However, little attention may have been paid to the increase in the basicity of coordinating atoms by substitution of the oxygen atoms with NH groups in crown ethers.In the present study, the formation constants of alkali metal complexes with monoaza-, diaza-, and polyazacrown ethers were obtained by means of mainly d.c. polarography; differential pulse polarography on DME and cyclic voltammetry on HMDE were additionally employed.The mercurydissolution processes of the macrocyclic compounds were clarified during the course of examining alkali metal ion complexation. The variation in the formation constants is discussed from the viewpoint of not only cavity size, but also the interaction between the Lewis acids and bases. The main purpose of the present study was to investigate the effects of the number of substitution of the oxygen atoms with NH groups in the crown ethers on the stabilities of the Li + and Na + complexs of 12-crown-4, 15-crown-5, and 18-crown-6.We have developed a new analytical method in d.c. polarography for obtaining the complex formation constant between cations and an anion which induces the mercurydissolution wave on DME. 6 This method was first successfully applied to the Li + -CH3COO-system in acetonitrile. The formation constants of a "reverse coordinated" species, CH3COO -(M + )2 (M + = Li + or Na + ), 6 and later that of (Li + )2Cl -7were obtained. Since then, we have revealed that the Li + ion operates an unexpectedly strong coordination ability in protophobic aprotic solvents. 8,9 Our method was found to be very useful for examining complex formation between alkali metal ions and macrocyclic polyamines (cyclam, tetramethylcyclam) 10,11 as well as acyclic polyamines (ethylenediamine, trien, tetren). 12The complex formation of cryptand[2.2] and its sulfur derivative (ATCO: 1,10-diaza-4,7,13,16-tetrathiacyclooctadecane) with alkali metal or alkaline earth metal ions in acetonitrile has been examined. 13 In principle, "the mercury-dissolution method" utilizes the The complex formation constants between alkali metal ions and monoaza-or diazacrown ethers (L) in acetonitrile have been obtained by the analytical method of d.c. polarography, in which a positive shift in E1/2 of the mercury-dissolution w...

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Interaction between Monoaza-, Diaza-, or Polyazacrown Ethers and Alkali Metal Ions in Acetonitrile by Polarography

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“…14 In acetonitrile, 1.0×10 -2 mol dm -3 p-TsOH solutions gave only a very small maximum after the half-equivalence point by the addition of 1.0 mol dm -3 Et 3 N solution.…”

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“…For obtaining association constants in the presence of higher aggregates, the conductivities of acids or salts were analyzed using our method. 4,14,18 Results and Discussion Figure 1 shows the conductometric titration curves of p-toluenesulfonic acid (p-TsOH, 25 ml) of various concentrations with triethylamine (Et 3 N) of the hundredfold concentrations in benzonitrile (PhCN) at 25˚C. When the concentration of p-TsOH was low (≤2×10 -3 mol dm -3 ), the conductance increased almost linearly with increasing amount of Et 3 N up to the equivalence point (250 µl).…”

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“…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 follows: NO 3 -<PhSO 3 -<p-TsO -<CH 3 SO 3 -.…”

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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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“…3 In the course of such studies, we have discovered that alkali metal and alkaline earth metal ions have unexpectedly strong interactions with simple anions, such as halide, 4 sulfonate, 5 tropolonate, 6 carboxylate, 7 and nitrophenolate 8 ions in aprotic solvents.…”

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Characterization of a Mixed-Anion Salt, BaCl(ClO4), Isolated from Acetonitrile Solution

et al. 2000

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In lower permittivity media (ε r < 10), ions may form higher aggregations, including triple ions, through Coulombic interactions. 1 We have found a linear relationship between triple ion formation constants and the salt concentrations at the minimum appeared in conductometric curves. 2 Higher ion aggregations from uni-univalent salts have been demonstrated even in higher permittivity media (20 < εr < 65) of very poor solvating ability. 3 In the course of such studies, we have discovered that alkali metal and alkaline earth metal ions have unexpectedly strong interactions with simple anions, such as halide, 4 sulfonate, 5 tropolonate, 6 carboxylate, 7 and nitrophenolate 8 ions in aprotic solvents.In a previous study, 9 the formation of stable carbocations from trityl(triphenylmethyl) and methoxy-substituted trityl halides in the presence of alkali metal (M + ) or alkaline earth metal (M 2+ ) ions in acetonitrile solution was observed by means of UVvisible spectroscopy. The γ -lactone rings of Rhodamine B and Crystal Violet lactone in the solvent were also cleaved by the addition of M + or M 2+. Very recently, we reported the observation by 1 H NMR 10 and 13 C NMR 11 of the formation of the stable carbocations from 4-methoxy-substituted trityl chlorides ((4-MeOC6H4)nPh3-nCCl: n = 1 -3) at higher concentrations, i.e., a preparative level, in the presence of alkali metal and alkaline earth metal perchlorates in acetonitrile at room temperature. The carbocations have been isolated as perchlorate salts from the acetonitrile solutions. The formation of the trityl cation from 4-methoxytrityl chloride at a higher concentration upon the addition of Ba(ClO4)2 in acetonitrile has been explained by Eq. (1).The complete ionization of 4-methoxytrityl chloride in the presence of Ba(ClO4)2 must be much indebted to the insoluble species (out of the system) in acetonitrile. The cation effects on the ionization of the trityl chlorides have increased as Li + < Mg 2+ < Na + < Ca 2+ < Sr 2+ < Ba 2+ . The precipitation reactions of the cations, excluding Li + and Mg 2+ , in acetonitrile are regarded as chemical reactions which promote greatly the ionization of the trityl chlorides. Our 1 H NMR data have verified that the stabilities of carbocations in the presence of alkali metal or alkaline earth metal ions increased as 4-methoxy-< 4,4′-dimethoxy-< 4,4′,4″-trimethoxytrityl derivative. 10In the present paper, metal precipitates formed in acetonitrile solution are characterized by chemical and instrumental analyses; and a novel salt, BaCl(ClO4), is proposed. ExperimentalCommercially obtained acetonitrile (Wako, GR grade) was used as received. 4-Methoxytrityl chloride (Aldrich, 97%) and 4,4′-dimethoxytrityl chloride (Aldrich, 95%) were used without further purification. The resources or purification methods of alkali metal and alkaline earth metal perchlorates, Et4NCl, and Et4NBr were mentioned previously. 6,9 Other reagents of analytical grade were used as received.IR spectra were obtained on a JASCO spectrometer FT/IR-5300 or a Hitachi...

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Spectrophotometric, polarographic and conductometric evidence for triple ion formation from benzenesulfonate and diphenyl phosphate salts in protophobic aprotic solvents

Cited by 31 publications

References 24 publications

Interaction between Monoaza-, Diaza-, or Polyazacrown Ethers and Alkali Metal Ions in Acetonitrile by Polarography

Interaction between Monoaza-, Diaza-, or Polyazacrown Ethers and Alkali Metal Ions in Acetonitrile by Polarography

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

Characterization of a Mixed-Anion Salt, BaCl(ClO4), Isolated from Acetonitrile Solution

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