Transfer thermodynamics of <i>p</i>-nitroaniline in aqueous solutions of some ionic and non-ionic cosolvents and the structuredness of the solvents

Datta, Jayati; Kundu, Kiron K.

doi:10.1139/v83-113

Cited by 19 publications

(11 citation statements)

References 13 publications

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“…As in previous papers (8,9), assuming the effect of activity coefficient factor to be negligibly small, the free energies of solutions AG! on the molar scale in the case of pNA and on the molal scale in the case of HBz were calculated for each solvent composition using eq.…”

Section: Resultsmentioning

confidence: 58%

“…The solubilities of HBz in mol kg-' and pNA in molarity in different solvent compositions as well as in pure water (9) are given in Table 4. Just as in aqueous organic solvents (8b, 9b) and salt solutions (9b, 11) of lower dielectric constant than water, the degrees of ionization (a,) of HBz in these salt solutions are also tentatively taken to be negligibly small as the dielectric constant decreases with increasing salt concentration (1) owing to the well known "dielectric decrement effect" (16,25).…”

Section: Resultsmentioning

confidence: 99%

“…The observed increased destabilization of pNA and HBz with increased proportion of ionic cosolvent NaN0, seemingly reflects the expected well known "saltingout" effect (14)(15)(16). It is also significant that unlike most aquoorganic solvent systems (9), the cavity effects are increasingly negative in this solvent system and thus largely obscures the expected salting-out effect in this solvent system when not duly corrected. Admittedly, however, although there are a number of theories to explain and quantify the salting-out and salting-in phenomena of various solutes including the ones studied here, they only achieve partial success (14)(15)(16)(17).…”

Section: A~ctoionization and Transfer Free Energiesmentioning

confidence: 98%

“…Similarly, although there are large number of studies (14-17) on salting-out and salting-in phenomena of various solutes, including benzoic acid (HBz) and p-nitroaniline (pNA), in various salt solutions and various theories have been proposed to explain the phenomena, so far very few attempts (1 1, 18, 19 have been made to study the temperature effects and the related structural changes of the solvent. However, in a series of papers 9) have recently demonstrated that ASP and particularly of p N A and HBz obtained by subtracting the cavity effect AS&,, (20) from AS: values, throw important suggestions on the structuredness of the aquoorganic solvents, as they are free from the "electrostatic" effect which confuses the structural content of AS: data of HX type of electrolytes (1-3, 8 , 9).…”

Section: Introductionmentioning

confidence: 99%

“…Significantly enough, the TAS?,, ,,,-composition profiles also show sharp downward trend both for p N A and HBz right from the beginning, as has been observed for these solutes in the respective salt solution referred to above. If one uses the semiquantitative theory of 9) for these solutes as a guide, then the observed sharply downward trend of TAS?,, ,,,-composition profiles in N a N 0 3 solutions is to be expected as a result of 3 D structure breaking propensity of the salt as observed earlier in other salt solutions.…”

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confidence: 99%

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Ion–ion–solvent interactions in aqueous ionic cosolvent systems. IV. Transfer energetics of water, p-nitroaniline, and benzoic acid from emf/solubility measurements at different temperatures in aqueous sodium nitrate solvent system

Rudra¹,

Talukdar²,

Kundu³

1988

Can. J. Chem.

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(K,) of aqueous mixtures of I , 2 , and 4 m sodium nitrate used as an ionic cosolvent system have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm) / KOH (m I ) KC1 (tn2), solvent / AgC1-Ag at five equidistant temperatures ranging from 15535°C. The standard free energies (AGO) and entropies (AS') of autoionisation of the solvents were then evaluated from these data. Relative free energies (AGO) and entropies (AS') of autoionization of the solvents when coupled with the previously determined transfer free energies [AG:(H+)] and entropies [AS:(H++)] of H' yielded AGY(OH),,, [= AGY(0H-) -AG:(H,O)], As:(OH-), and ASF(H20). Values of AG:(Ht.) and A G Y ( 0 H ) obtained after correcting for AG;(H~o), as well as A@,,,,in,(H+) and AGfl,i,,(O~-) obtained after correcting the "cavity effect" and Born-type electrostatic effect suggests that while the "basicity" of the aqueous NaN03 solutions decreases, the "acidity" more or less increases with NaN03 concentration. The observed A$,,,.i,,(OH-)-and A~l r , i , , (~,~) -c o m p o s i t i o n profiles were also examined in the light of Kundu et al.'s four-step transfer process and the involved order-disorder phenomena, respectively, as proposed earlier.Standard free energies (A@) and entropies (AS:) of transfer of p-nitroaniline (pNA) and benzoic acid (HBz) for the solvent system have also been determined from solubility measurements at different temperatures. The observed AGY-and AGf,,,in,-composition profiles appear to reflect the salting-out effect of the salt and the AS,' -and A$,,,,in,-composition profiles confirm the applicability of either of these quantities rather than A$.,r,i,,(HX), as a better structural probe both for aquo-ionic and aquo-organic solvents. [Traduit par la revue] Introduction In our previous papers (1-3) we have reported the thermodynamics of HX, X = C1 (I), Br, and I (3), and also the transfer energetics of some electrolytes and the related "ion-ionsolvent" interactions (2) in aqueous solutions of 1, 2, and 4 rn NaN03 taking each composition as an individual solvent and taking the infinitely dilute solution of solutes in each solvent as the standard state as in aquo-organic solvent systems.Since autoionization constants of water in aquo-organic solvents reflect acidity and basicity of the solvents, it would be of particular interest to evaluate the same for this solvent system as well. Moreover, it is now increasingly recognised that thermodynamics of autoionization of water and the transfer energetics of various non-electrolytes including water, provide useful information regarding the three dimensional (3D) "structuredness" of the solvent (4-13). The basis of structural

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Section: Resultsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%