An electrostatic model for hydrogen bonds in alcohols

Giguère, Paul A.; Pigeon-Gosselin, Marie

doi:10.1007/bf00647798

Cited by 21 publications

(11 citation statements)

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“…[22][23][24][25][26][27][28] Recently, an alternative microscopic origin was proposed that the isosbestic point can arise from the statistical thermal distribution of harmonic oscillators in a continuous distribution of structures, and therefore should not be used as evidence or fingerprint of multistate (discrete cluster distribution) behavior. 17,18 The temperature-dependent Raman spectra of liquid methanol in the -OH stretching region have already been recorded for many years, 28,29 but the spectral analysis was based on the socalled linear-bifurcated-trifurcated HB model in a continuously hydrogen-bonded network, 29 which is not consistent with the widely employed cluster model. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]30,31 In fact, different from liquid water in which a tetrahedral H-bonding network forms, liquid methanol should be in some respects simpler than water, since much fewer hydrogen bonds can be formed in it.…”

Section: Resultsmentioning

confidence: 99%

The Microscopic Structure of Liquid Methanol from Raman Spectroscopy

et al. 2010

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The microscopic structure of liquid methanol has been systematically investigated with Raman spectroscopy in a temperature range of 15-55 degrees C. The unbonded free -OH stretching vibrational band has been observed at approximately 3660 cm(-1) in pure liquid. With the aid of depolarization measurements and theoretical calculations, four featured spectral components have been unambiguously identified and assigned to four well-defined vibrational modes of clusters in chain or ring forms. Furthermore, the cluster size distribution and its temperature dependence have been derived from the spectral fittings for the first time, which lead to the conclusion that the trimer, tetramer, and pentamer are the dominant clusters in liquid methanol, taking up more than 50% of total clusters.

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Section: Resultsmentioning

confidence: 99%

The Microscopic Structure of Liquid Methanol from Raman Spectroscopy

et al. 2010

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“…The observed temperature isosbestic point can indeed be easily rationalized as the result of straightforward changes in a continuous distribution of hydrogen bonding geometries, with no need to invoke distinct classes of solvation structure. Two-state pictures inspired by the appearance of isosbestic points in a variety of systems, including other solutes in water [23][24][25] and other liquids such as methanol, 26,27 should be similarly reconsidered.…”

Section: Discussionmentioning

confidence: 99%

Temperature Dependence of Inhomogeneous Broadening: On the Meaning of Isosbestic Points

Geissler

2005

J. Am. Chem. Soc.

104

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An isosbestic point in the temperature dependence of an absorption spectrum is commonly viewed as a sign of interconverting chemical or structural species. Here I explore an alternative microscopic origin of temperature-independent absorbance in inhomogeneously broadened spectra: While the equilibrium probability of observing a particular frequency generally changes with the magnitude of thermal fluctuations, the weight of at least one frequency is insensitive to small changes in temperature. The range of temperature accessible to aqueous solutions at ambient pressure is sufficiently small that such insensitivity would appear in experiments as an isosbestic point. This mechanism depends only on the continuity of equilibrium distributions, not on the presence of multiple components. Even the simplest model of a single solute species in a fluctuating environment exhibits isosbestic points, van't Hoff behavior, and, with appropriate dependence of transition frequency on configuration, multiple absorption peaks.

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“…Giguere discussed the presence of bifurcated hydrogen bonds (BHB) based on the results of the temperature changes of the O-H stretching bands in the Raman spectra and the neutron diffraction of heavy water22 and pure methanol. 23 He estimated the 0-0 distances between the outer two water molecules connected with the central water through BHB to be 4.2 A by keeping the nearest-neighbor 0-0 distance at 2.8 A (ice site). The angle between the two BHB is 97°in this case.…”

Section: Discussionmentioning

confidence: 99%