Molecular association of hydrogen-bonding solutes. Phenol in carbon tetrachloride

Self Cite

The intermolecular hydrogen-bonding self-association of the three cresols in CC1, solutions a t 25 "C has been investigated by calorimetric means. Calorimetrically determined heats of dilution of each of the cresols in anhydrous CCI4 are interpreted in terms of two different models: (i) dimerization and trimerization self-association reactions, and (ii) dimerization followed by stepwise polymerization self-association reactions. Values of K, AH0, and ASOfor these reactions are calculated using least-squares and other methods. Results show that o-cresol is clearly less associated in anhydrous CCI, solution at 25 "C than either m-or p-cresol. Values of K, and K, (both based on molar concentrations of solutes) and AHZO and AH30 (kcal) for the reactions 2C C, and 3C+ C,, respectively, are o-cresol: 0.7, I.,, -3.,, -12.,; m-cresol: 0.8, 5.,, -5.0, -13.,; p-cresol: 0.3,, 6.,, -5.5, -13.,. Values of K, and K, (both based on molar concentrations of solutes) and AH,, and AH? (kcal) for the reactions 2C $ Cz and

Section: Resultsmentioning

confidence: 99%

“…1-4) of phenols in CCI, and in other "inert" solvents have been interpreted in terms of monomerdimer equilibrium. There is now evidence, however, that associated species larger than dimers are important in all but the most dilute solutions (3,4). Mecke (5) reviews i.r.…”

Section: Introductionmentioning

confidence: 99%

Molecular Association of Hydrogen Bonding Solutes, o-, m-, and p-Cresol, in Carbon Tetrachloride

Woolley¹,

Rushforth²

1974

Self Cite

“…In view of the two well known resonance structures of the amide group (I), it is reasonable to assume that like alkanols (2)(3)(4)(5), the lower amides in the pure state exist as dimers, trimers, or higher r-mers. Davies ( 6 ) , however, maintains that the association of amides in solution is limited to dimer formation.…”

Section: Introductionmentioning

confidence: 99%

Topological investigations of the volumetric and enthalpic effects in some binary mixtures of non-electrolytes

Singh¹,

Bhatia²

1990

PREM P. SINGH and MEENU BHATIA. Can. J. Chem. 68, 74 (1990).Volumetric and enthalpic effects have been measured at 308.15 K for pyridine (A) + aniline, o-toluidine, formamide, or N,N-dimethylformamide (B) mixtures and the same have been rationalized by graph-theoretical arguments to suggest that while aniline in the pure state exists as an equilibrium mixture of monomers and dimers, o-toluidine exists mainly as dimers. This analysis has further yielded information about the state of association in formamide and N,N-dimethylformamide that is consistent with the existing views on their nature of association. This analysis has further yielded information about the molecular entities in these mixtures that has been supported by their infrared spectral studies. The energetics of the various interactions that result in the formation of these A + B mixtures have also been investigated and the results have been rationalized by graph-theoretical arguments.Key words: topological, association, solvation, energetics, volumetric, enthalpic effects.PREM P. SINGH et MEENU BHATIA. Can. J. Chem. 68, 74 (1990).Operant il 308,15 K, on a mesurk les effets volumCtriques et enthalpiques de mtlanges de pyridine (A) avec les composes suivants (B) : I'aniline, 1'0-toluidine, la formamide et la N,N-dimCthylformamide; en se basant sur la thCorie des graphes, on suggbre que I'aniline il 1'Ctat pur existe sous la forme d'un Cquilibre entre des monombres et des dimbres alors que 1'0-toluidine existe principalement sous la forme de dimbres. Cette analyse a aussi fourni des informations concernant l'ttat d'association dans la formamide et la N,N-dimCthylformamide et ces informations sont en accord avec les vues gCnCralement acceptkes concernant la nature de I'association qui existe dans ces composCs. Cette analyse a aussi fourni de I'information concernant les entitCs molCculaires prksentes dans ces melanges; ces informations sont en accord avec les donnCes obtenues en se basant sur les spectres infrarouges de ces mtlanges. On a aussi examine les Cnergies impliqutes dans les diverses interactions qui conduisent il la formation de ces A + B melanges et on a rationalis6 les rCsultats il l'aide d'arguments basts sur la thtorie des graphes.

“…The method is attractive because it is potentially applicable to a wide variety of systems. The solute can be either an electrolyte (1,2) or a nonelectrolyte (3). The experimental temperature can readily be varied (2,4) and the choice of nonaqueous solvents is limited only in that the solvent must be immiscible with water.…”

Section: Introductionmentioning

confidence: 99%

“…We therefore seek a system with the following properties: (I) the aqueous phase concentration of the solute in the partition experiments should be low. This is to ensure that complications due to possible nonideality of the solute in the aqueous phase are minimal; (2) the extent of hydration of the solute in the organic phase should be very small, so that the above mentioned uncertainties in the correction for hydration are small; (3) the binary system consisting of the solute in the anhydrous organic solvent should be amenable to study by classical thermodynamic methods, so that thermodynainic data are available for comparison with the data obtained by partition.…”

Section: Introductionmentioning

confidence: 99%

The Dimerization Constant of Nitrobenzene in Benzene: A Critique of Partition as a Thermodynamic Method

Goldman¹,

Duer²

1974

The dimerization constant (K) of nitrobenzene in benzene was determined at 5.5 and 25 °C by means of partition (solvent extraction). A hydration study was performed at these temperatures to determine the extent of hydration of nitrobenzene in the benzene phase. Published freezing point depression data for the anhydrous benzene–nitrobenzene system were used to obtain a value of K at 5.5 °C. The heats of solution of nitrobenzene in benzene (anhydrous) were determined at 25 °C. The heat of solution and freezing point depression data were combined to obtain a value of K for the anhydrous system at 25 °C. At each of 5.5 and 25 °C the value of K determined by partition was significantly smaller than the corresponding value of K for the anhydrous system, and the discrepancy was larger at 25 than at 5.5 °C. It was found that by fitting a simple electrostatic model to the difference in the values of K found at 5.5 °C, the difference at 25 °C could be predicted.