The molecular association of some carboxylic acids in aqueous solutions from conductivity data

Cartwright, D.; Monk, C. B.

doi:10.1039/jr9550002500

Cited by 31 publications

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“…Similar effects were observed in /3-alanine3-although not in -alanine-and were also found to be strongly present in several aliphatic diamines and the conjugate diammonium ions. 6 Our present studies show that the effect of the -NH2 or -NH3+ group in perturbing the C-D stretching vibrations is very similar to the previously observed effects on the G-H vibrations, although there are differences in detail.…”

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confidence: 88%

Raman Spectra of Carbon-Deuterated Glycine in Various Ionic Forms

Ghazanfar¹,

Myers²,

Edsall³

1964

J. Am. Chem. Soc.

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Raman spectra are reported for C-deuterated glycine ( +H,jS-CDz-COO-) in the form of the dipolar ion dissolved in HzO, and also for the conjugate cation in acid solution, and for the anion in alkaline solution. Similar studies are reported for completely deuterated glycine (+D,X-CD,-COO-) in D20 in all three forms and for ordinary glycine ( +H,S-CH,-COO-) in Hz0. The data were photoelectrically recorded ; quantitative intensity measurements and semiquantitative depolarization values are reported. In confirmation of earlier photographic measurements from this laboratory by Takeda, el al., it is found that the two C-H stretching frequencies of ordinary glycine a t 2975 and 3010 cm.-l, which are sharp and quite distinct in solutions of the cation and dipolar ion, become fused into a single broad band in the anion, and the frequency shift decreases to about 2935 cm.-'. In C-deuterated glycine in HzO the corresponding frequencies lie between 2100 and 2270 cm.-l; there are, however, three distinct peaks instead of two. The downward displacement of the C-H stretching frequencies in the anion, a s compared with the cation or dipolar ion, is similar to the displacement observed in ordinary glycine. Similar relations are observed for the C-D stretching frequencies in C-deuterated glycine in DzO, but there is some overlap between one of the C-D vibrations and the S-11 stretching frequency near 2200 cm.-l t h a t is characteristic of the charged -S D s f group. The frequencies characteristic of the carboxyl group are scarcely affected a t all by ionization of the amino group, or by deuteration of either the amino group or the a-carbon atom.

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supporting

confidence: 88%

Raman Spectra of Carbon-Deuterated Glycine in Various Ionic Forms

Ghazanfar¹,

Myers²,

Edsall³

1964

J. Am. Chem. Soc.

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“…The carboxyl group can be both a hydrogen bond donor (through the hydroxyl group) and an acceptor (through the carbonyl group). [3][4][5] The double hydrogen bonding character enables carboxylic acids to establish a strong intermolecular bond which leads them to form very stable dimers. This is reflected in their physical properties.…”

Section: Introductionmentioning

confidence: 99%

Measuring acetic acid dimer modes by ultrafast time-domain Raman spectroscopy

Heisler

Mazur

Yamaguchi

et al. 2011

Phys. Chem. Chem. Phys.

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Acetic acid is capable of forming strong multiple hydrogen bonds and therefore different dimeric H-bonded structures in neat liquid phase and in solutions. The low frequency Raman spectra of acetic acid (neat, in aqueous solution and as a function of temperature) were obtained by ultrafast time and polarization resolved optical Kerr effect (OKE) measurements. Isotropic OKE measurements clearly reveal a specific totally symmetric mode related to the dimeric structure H-bond stretching mode. The effects of isotope substitution, water dilution and temperature on this mode were investigated. These results together with anisotropic OKE measurements and density functional theory calculations for a number of possible dimers provide strong evidence for the cyclic dimer structure being the main structure in liquid phase persisting down to acetic acid concentrations of 10 M. Some information about the dimer structure and concentration dependence was inferred.

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“…From the best fit to the data of MacDougall and Blumer5 we found that partial pressure of anhydrous monomeric acetic acid = 3(mole fraction of [HA• H20 + HA] in solution) (7) Equating the two expressions ( 6) and ( 7) for the partial, pressure of anhydrous monomeric acetic acid, we get: 150(mole fraction of HA) = 3(mole fraction of [HA• H20 + HA]) (8) Equation 8 shows that in the solutions with which Mac-Dougall and Blumer worked, the ratio of hydrated to anhydrous acetic acid is in the neighborhood of 50 to 1, and therefore it may be safely assumed that the monomer represented by the Raman line at 1710 cm-1 is the hydrated monomer occurring in eq 5. In applying eq 6 to predominantly aqueous solutions we assumed that the activity coefficient of anhydrous monomeric acetic acid is substantially unchanged in going from glacial acetic acid to water, an approximation we consider sufficiently good for our purposes.…”

Section: Results and Conclusionmentioning

confidence: 94%

Conductivity anomalies of aqueous carboxylic acid solutions. Dimerization or effect of solvent medium

Simpson¹

1975

J. Phys. Chem.

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The low conductivity of concentrated aqueous solutions of fatty acids cannot be explained by the model of a cyclic dimer proposed by Katchalsky, Eisenberg, and Lifson because (1) the "dimerization constants" of homologs calculated on this basis are inconsistent with the model; (2) "dimerization constants" calculated frqm conductivity are larger than those from other data (this includes vapor pressure data if the presence of hydrated fatty acids in the vapor phase is recognized); (3) Raman spectra published by Koteswaram and confirmed in this paper show very little cyclic dimer in predominantly aqueous solutions of fatty acids. In these solutions the dimerization constant calculated from Raman spectra is approximately 0.01 M-1. Most of the anomaly in the conductivity or electromotive force cannot be due to dimerization, but must be ascribed to the replacement of water by un-ionized fatty acid in the solvent medium. The medium effect must still be regarded as empirical, since attempts to calculate its value from the properties of the medium have not been successful.

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The molecular association of some carboxylic acids in aqueous solutions from conductivity data

Cited by 31 publications

References 0 publications

Raman Spectra of Carbon-Deuterated Glycine in Various Ionic Forms

Raman Spectra of Carbon-Deuterated Glycine in Various Ionic Forms

Measuring acetic acid dimer modes by ultrafast time-domain Raman spectroscopy

Conductivity anomalies of aqueous carboxylic acid solutions. Dimerization or effect of solvent medium

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