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Journal ArticleDOI

Electric Polarization of Carboxylic Acids in Dilute Solutions of Nonpolar Solvents I. The Relation of Electric Polarization to the Association of Carboxylic Acids in Hydrocarbon Solvents

01 May 1941-Journal of Chemical Physics (AIP Publishing)-Vol. 9, Iss: 5, pp 408-414
TL;DR: In this paper, the association and polar character of various carboxylic acids have been studied in the solvents benzene and heptane by means of measurements of the electric polarization in very dilute solutions.
Abstract: The association and polar character of various carboxylic acids have been studied in the solvents benzene and heptane by means of measurements of the electric polarization in very dilute solutions. The data have been analyzed by assuming an equilibrium between dimers and monomers of the acid molecules. A rather large anomalous contribution to the polarization of the dimer has been found. Possible origins of this polarization have been briefly considered.
Citations
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TL;DR: In this article, the hydrogen bonding effect on the fluorescence of quinoline and acridine was studied in non-polar solvent mixed with various proton donors, and the equilibrium constants of hydrogen bonding calculated from the absorption and fluorescence data were the same for these molecules, in contradistinction to the case of naphthols.
Abstract: 1. The hydrogen bonding effect on the fluorescence of quinoline and acridine was studied in non-polar solvent mixed with various proton donors.2. The equilibrium constants of hydrogen bonding calculated from the absorption and fluorescence data were the same for these molecules, in contradistinction to the case of naphthols. Possible mechanisms for this experimental fact were proposed.3. The larger the relative fluorescenceyields of hydrogen bonded nitrogen heterocycles become, the stronger the donating powers of proton donors are, and from this fact, discussions were given on the role of non-bonding electrons in the inner-quenching of these molecules.4. The difference between quinoline and acridine in their fluorescence quenching caused by the existence of a halogen atom was ascribed to the different emitting π-electronic states in these molecules (1Lb in quinoline, 1La in acridine), and some considerations by means of analogy to the π-electronic structures of aromatic hydrocarbons were given.

124 citations

Journal ArticleDOI
TL;DR: In this article, the infra-red spectra of benzoic acid in the vapour phase, and in dilute solution in cyclohexane, carbon tetrachloride, and benzene show two bands between 1770 and 1670 cm−1 which are assigned respectively to free and carbonyl groups involved in hydrogen bonding between acid molecules.

89 citations

Journal ArticleDOI
TL;DR: In this paper, the authors derived an equation for the excess acoustic absorption in a liquid system due to the occurrence of a chemical reaction; the method used follows in part that used by Damkohler in the case of gases.
Abstract: An equation is derived for the excess acoustic absorption in a liquid system due to the occurrence of a chemical reaction; the method used follows in part that used by Damkohler in the case of gases. It is shown that the gross reaction rate at equilibrium can in general be found once the frequency at which the maximum excess absorption per wavelength occurs has been found, provided thermodynamic data for the reaction are known.The application of this method to the study of the kinetics of very rapid reactions is discussed and the effects of other causes of absorption are considered.As another application of the results obtained the acoustic absorption of acetic and propionic acids is considered. A consistent interpretation of data in the literature is given on the assumption that the excess absorption is due to the perturbation of an equilibrium between monomeric and dimeric molecules. The mole fraction equilibrium constant KN, and the heat of reaction for the dimerization are calculated. The values found...

75 citations

Journal ArticleDOI
TL;DR: In this paper, a homologe Reihe der aliphatischen Lactame (III, n − 15 bis 19) bietet the Moglichkeit des vergleichenden Studiums von cis-und trans-Amiden im Losungszustand.
Abstract: N-Monosubstituierte Saureamide, wie sie in der Peptidbindung vorliegen, vermogen in cis-trans-isomeren Plankonfigurationen aufzutreten. Die homologe Reihe der aliphatischen Lactame (III, n – 15 bis 19) bietet die Moglichkeit des vergleichenden Studiums von cis-und trans-Amiden im Losungszustand. Das Absinken der Molpolarisation der Lactame III, n = 5–9 mit zunehmender Konzentration zeigt die nur mit der cis-Amidgruppe vereinbare Assoziation zum cyclischen Dimeren an. Die mit der Konzentration ansteigende Molpolarisation von III, n = 10–19 weist auf eine Kettenassoziation unter Momentvergroserung, wie sie der trans-Amidgruppe eigen ist. Bis zum 8-gliedrigen Lactamring findet sich die cis-Konfiguration erzwungen, wahrend vom 10-gliedrigen an aufwarts die an sich bevorzugte trans-Form spannungsfrei moglich wird; III, n = 9 nimmt eine Ubergangstellung ein. Die Dipolmomente der monomeren cis- und trans-Amide sind nahezu gleich; fur die Bevorzugung der trans-Konfiguration mus somit ein Orthoeffekt verantwortlich sein. Die Assoziationskonstanten der cis-Lactame und die elektrischen Momente der cyclischen Dimeren wurden bestimmt.

75 citations

Journal ArticleDOI
TL;DR: In this article, Fourier transform infrared (FTIR) spectroscopy has been used to determine the equilibrium constants of the dimerization for carboxylic acid (acetic acid or palmitic acid).
Abstract: Supercritical fluid extraction has been given much attention recently as one of the new separation technologies in the chemical industry. Fourier transform infrared (FTIR) spectroscopy has been used to determine the equilibrium constants of the dimerization for carboxylic acid (acetic acid or palmitic acid) and the amount of hydrogen bonding species between carboxylic acid and ethanol in supercritical CO{sub 2}. Experiments were carried out at 308.2--313.2 K and 10.0--20.0 MPa. The noticeable band was the C{double_bond}O stretching band for carboxylic acid. In the binary system (supercritical CO{sub 2} + carboxylic acid), the equilibrium constants of the dimerization between the carboxylic acid monomer and dimer decrease with increasing pressure and temperature. The equilibrium constants of palmitic acid are larger than those of acetic acid. In a ternary system (supercritical CO{sub 2} + carboxylic acid + ethanol), the amount of hydrogen bonding species between carboxylic acid and ethanol in supercritical CO{sub 2} increases with the increasing mole fraction of added ethanol. Furthermore, the authors confirm that the solubility enhancement by ethanol used as an entrainer in supercritical CO{sub 2} related to the amount of hydrogen bonding species between carboxylic acid and ethanol.

49 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a list of the formulae which had been proposed at the time of the Faraday Society's discussion is collated by Goss, and the theory formula of Weigle is omitted from this list.
Abstract: It has been conclusively proved in the last two years that there is a significant effect of the solvent on the measured value of dipole moment of a solute. It has also been shown that the effect is mainly determined by the dielectric constant of the medium, suggesting a relatively simple physical cause, but the precise law of relationship is still disputed. A list of the formulae which had been proposed at the time of the Faraday Society's discussion is collated by Goss. These all have the status of empirical formulae, since that of Raman and Krishnan contains two difficult accessible constants. The theory formula of Weigle is omitted from this list. It receives some discussion in the next section of this paper. These formulae agree in disregarding the properties of the solute, excepting its dipole moment. The solvent effect is considered to be proportionately the same for all polar substances. Muller makes an exception in suggesting a modified law for certain substances, mainly ketones. The hydrogen halides, with positive solvent effects, are considered entirely anomalous, and their increase of moment is attributed to an intramolecular change towards more ionic linkage.

25 citations

Journal ArticleDOI
TL;DR: In this article, a detailed discussion of the methods employed for interpreting and analyzing the results from the standpoint of the association of the solutes is aIso incIuded, and a description of some of the improvements which were made in apparatus and methods in order to carry out dielectric polarization measurements in very low concentrations in non-polar solvents under anhydrous conditions.
Abstract: The effective use of dielectric polarization measurements in investigating the association of polar molecules in non-polar solvents has been largely confined to a study of the association of alcohols. These show significant changes in their state of aggregation in a range of concentrations sufEiciently high so that the equipment and methods hitherto available for dielectric constant measurements in solutions can be successfully applied to the investigation of their extent of association. The case of the carboxylic acids in non-polar solvents is quite different. Freezing point determinations show that extremely low concentrations must be attained before significant changes in the state of aggregation occur. This range of concentrations in the case of many of the acids lies below 2 X mole fraction. As a consequence it has been difficult to make sufficiently accurate measurements by most of the methods for molecular weight determination in solution to yield quantitative information about the molecular state of these acids in dilute solution in non-polar solvents. While it has been possible to use the freezing point method, this is applicable only a t a single temperature and so gives information about temperature coefficients and energies of association only through the use of estimates made at other temperatures by other methods. In this paper a description will be given of some of the improvements which were made in apparatus and methods in order to carry out dielectric polarization measurements in very low concentrations in non-polar solvents under anhydrous conditions. In view of the low concentrations involved it is necessary to include a comprehensive statement of the errors of the method. A detailed discussion of the methods employed for interpreting and analyzing the results from the standpoint of the association of the solutes is aIso incIuded.

8 citations