Hydrogen bonding in liquid methanol and ethanol determined by x-ray diffraction

Narten, A. H.; Habenschuss, A.

doi:10.1063/1.447093

Cited by 291 publications

(221 citation statements)

References 23 publications

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“…The average intramolecular O -C distance in the liquid, roc, is needed for the evaluation of the correlation time r 2 from the measured relaxation time Ti. Values of r^ = 1.44 Ä are found in the liquid phase from neutron [12] and X-ray [13,14] diffraction. These values are slightly larger than the ones reported for the gas phase, 1.42-1.43 Ä [15][16][17][18].…”

Section: Experiments and Simulationsmentioning

confidence: 99%

The Anisotropy of the Molecular Reorientational Motions in Liquid Methanol

Ludwig

Bopp

Zeidler

1995

Zeitschrift Für Naturforschung A

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Dedicated to Professor W . Müller-Warmuth on the occasion of his 65th birthday Nuclear magnetic resonance (NMR) relaxation time measurements on isotopically substituted samples yield a detailed understanding of the molecular reorientational dynamics in liquids. Reori entational correlation times obtained from such experiments are reported for two molecule-fixed vectors in pure liquid methanol. While the reorientational motions of single molecules are nearly isotropic at temperatures below 250 K, at 308 K the reorientational correlation time of the O-H vector becomes 2.3 times larger than that of the O-C vector. Molecular dynamics (MD) simulations give access to the complete correlation functions of the reorientational motions. Correlation times extracted from these functions fit well to the experiment in case of the O-C vector. At low temper atures, however, these times lie markedly above those obtained in the experiment for the O-H vector. Thus, the simulation yields reorientation times for the O-H vector that are, independent of the temperature, twice as large as those of the O-C vector.

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Section: Experiments and Simulationsmentioning

confidence: 99%

The Anisotropy of the Molecular Reorientational Motions in Liquid Methanol

Ludwig

Bopp

Zeidler

1995

Zeitschrift Für Naturforschung A

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“…Namely, chains-like structures for methanol(CH 3 OH) (MetOH) and micellelike structure for tert butanol((CH 3 ) 3 COH) (TBA). The first type of structure has been studied previously by many authors and by various techniques [4,12,13]. It is often a matter of debate as to know in which exact form these chain-like structures appear, such as rings, lassos and so on.…”

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confidence: 99%

Microstructure of neat alcohols

2007

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Formation of microstructure in homogeneous associated liquids is analysed through the densitydensity pair correlation functions, both in direct and reciprocal space, as well as an effective local one-body density function. This is illustrated through a molecular dynamics study of two neat alcohols, namely methanol and tert-butanol, which have a rich microstructure: chain-like molecular association for the former and micelle-like for the latter. The relation to hydrogen bonding interaction is demonstrated. The apparent failure to find microstructure in water -a stronger hydrogen bonding liquid-with the same tools, is discussed.Liquids are generally thought as macroscopically homogeneous when they are considered far from phase transitions and interfacial regions. From a statistical mechanical point of view, homogeneity is expressed by the fact that the order parameter, in this case the one body density, which formally depends on both the position and orientation of a single particle 1 (as in a crystal or a liquid crystal, for example), is a constant throughout the sample: ρ (1) (1) = ρ = N/V , where N is the number of particles per volume V. As a consequence, the microscopic description of the structure of a neat liquid starts from the two-body density function ρ (2) (1, 2) = ρ (1) (1)ρ (1) (2)g(1, 2) that expresses the density correlations between particles 1 and 2, and reduces in this case to ρ 2 g(1, 2) , where g(1, 2) is the pair distribution function. Associated liquids, such as water and alcohols, for example, belong to a special class because of the particularity of the hydrogen bonding (HB) that is highly directional, and tend to enhance the structure the liquid locally. One particularly interesting example of this phenomena is the microheterogeneous nature of aqueous mixtures, which has attracted a recent upsurge of interest [1,2,3,4,5,6,7]. Perhaps the most remarkable reported fact is that watermethanol mixtures show local immiscibility at microscopic level, while being miscible at macroscopic level [1,2]. In order to appreciate this result it is interesting to compare it to microemulsions where bicontinuous phases are usually observed, and micro-immiscibility operates with domain sizes ranging from 100 nanometers to few micrometers, while those mentioned here are around few nanometers-that is about few molecular diameters. In addition, it is important to note that bicontinuous phases in microemulsions arise after a phase transition has occurred from disordered to ordered phase; while in the former case, we are still in a genuinely homogeneous and disordered liquid phase. From these facts, microheterogeneity in aqueous mixtures can be considered as both obvious and mysterious, obvious because the mechanism behind it is the strong directionality of the hydrogen bonding, and mysterious because of the existence of stable microimmiscibility of water and solute in a macroscopically homogeneous sample. In contrast to the situation for mixtures, neat water do not seem to exhibit any micro phase separation betwe...

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“…The values of A = B = 0.264± 0.008 D and r AB = 2.798± 0.006 Å are known, 26,27 but the angle between the transition dipoles of the two CD 3 OH molecules will vary from pair to pair. To obtain an upper limit for the transition-dipole coupling, we calculate ␤ dipole for the case of parallel transition dipoles, for which we find ␤ dipole =−32±2 cm −1 .…”

Section: ⌬E 11mentioning

confidence: 99%

Simultaneous photon absorption as a probe of molecular interaction and hydrogen-bond cooperativity in liquids

Woutersen

2007

The Journal of Chemical Physics

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We have investigated the simultaneous absorption of near-infrared photons by pairs of neighboring molecules in liquid methanol. Simultaneous absorption by two OH-stretching modes is found to occur at an energy higher than the sum of the two absorbing modes. This frequency shift arises from interaction between the modes, and its value has been used to determine the average coupling between neighboring methanol molecules. We find a rms coupling strength of 46±1cm−1, larger than can be explained from a transition-dipole coupling mechanism, suggesting that hydrogen-bond mediated interactions also contribute to the coupling. The most important aspect of simultaneous vibrational absorption is that it allows for a quantitative investigation of hydrogen-bond cooperativity. We derive the extent to which the hydrogen-bond strengths of neighboring molecules are correlated by comparing the line shape of the absorption band caused by simultaneous absorption with that of the fundamental transition. Surprisingly, neighboring hydrogen bonds in methanol are found to be strongly correlated, and from the data we obtain an estimate for the hydrogen-bond correlation coefficient of 0.69±0.12.

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Hydrogen bonding in liquid methanol and ethanol determined by x-ray diffraction

Cited by 291 publications

References 23 publications

The Anisotropy of the Molecular Reorientational Motions in Liquid Methanol

The Anisotropy of the Molecular Reorientational Motions in Liquid Methanol

Microstructure of neat alcohols

Simultaneous photon absorption as a probe of molecular interaction and hydrogen-bond cooperativity in liquids

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