Molecular Reorientation in Liquid Methanol

Ludwig, Ralf; Gill, Dip Singh; Zeidler, Manfred

doi:10.1515/zna-1991-1-214

Cited by 51 publications

(38 citation statements)

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“…The experimental data exhibit a faster growth for τ 2,w OH in comparison with results of the simulation models under study. For pure methanol, Ludwig et al [39] reported τ 2, m OH = 5.1 ps, but mentioned that the simulation results are quite sensitive to the force field, thus leading to a value in the wide interval of 2-5 ps. Our value for methanol is slightly less than 3 ps, showing a faster relaxation than apparently it comes out from the experiment.…”

Section: Dynamic Propertiesmentioning

confidence: 99%

Composition dependence of thermodynamic, dynamic and dielectric properties of water–methanol model mixtures. Molecular dynamics simulation results with the OPLS-AA model for methanol

Galicia‐Andrés

Domínguez

Pusztai

et al. 2015

Journal of Molecular Liquids

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Section: Dynamic Propertiesmentioning

confidence: 99%

Composition dependence of thermodynamic, dynamic and dielectric properties of water–methanol model mixtures. Molecular dynamics simulation results with the OPLS-AA model for methanol

Galicia‐Andrés

Domínguez

Pusztai

et al. 2015

Journal of Molecular Liquids

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“…A number of recent investigations have reported molecular correlation times for water, simple alcohols and binary solutions of alcohols that are based on the measurement of proton spin lattice relaxation times of oxygen-17 enriched samples [1][2][3][4][5] . For protonated samples the spin-lattice relaxation rate, R1, for protons interacting with other protons is given by the dipolar relaxation equation: …”

Section: Introductionmentioning

confidence: 99%

“…Deuterium relaxation time experiments are attractive since the deuterium quadrupole coupling constant, χD, is typically ten times greater than dipolar coupling; consequently, intermolecular interactions can be ignored. For a spin-1 nucleus such as 2 H the relaxation rate, R 1 is given by:…”

Section: Introductionmentioning

confidence: 99%

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

Farrar

Wendt

Zeidler

1999

J. Braz. Chem. Soc.

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O uso de amostras de álcoois enriquecidas com 17 O, para medir o tempo de correlação do vetor internuclear OH funciona bem quando o próton da hidroxila sofre uma troca rápida. Para álcoois tais como metanol e etanol, a taxa de troca da hidroxila para amostras puras é relativamente lenta, mesmo à temperatura ambiente, podendo resultar em erros sistemáticos significativos se efeitos de troca lenta não forem considerados. Para trocas lentas do próton da hidroxila, 17 OH, o sinal é uma função relativamente complexa da razão de troca química do próton da hidroxila, do acoplamento de spin OH (cerca de 80 Hz para álcoois e água) e do tempo de relaxação para o oxigênio. A largura de linha do OH pode tornar-se tão grande, devido à relaxação escalar com o núcleo de oxigênio, que o sinal torna-se muito difícil de detectar. Para etanol puro enriquecido com 17 O, à temperatura ambiente, o tempo de relaxação do oxigênio é de aproximadamente 3,0 ms e a largura de linha do próton da hidroxila é maior do que 1000 Hz.The use of 17 O enriched samples of alcohols to measure the correlation time of the OH internuclear vector works well when the hydroxyl proton exchanges rapidly. For alcohols such as methanol and ethanol the hydroxyl exchange rate for neat samples is relatively slow even at room temperature and significant systematic errors result if slow exchange effects are not considered. For slow exchange the hydroxyl proton, 17 OH, signal is a relatively complex function of the chemical exchange rate of the hydroxyl proton, the OH spin coupling (about 80 Hz for alcohols and water) and the relaxation time for the oxygen. The OH linewidth can become so large due to scalar relaxation with the rapidly relaxing oxygen nucleus that the signal becomes very difficult to detect. For neat 17 O enriched ethanol at room temperature the oxygen relaxation time is about 3.0 ms and the hydroxyl proton linewidth is over 1000 Hz.

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“…Several solid state NMR studies of single crystals of hydrated salts 3 and of single crystals of amino acids 4 have shown that the QCP is related to the inverse cube of the hydrogen-bond distance. Quite recently solution state NMR studies of water 5-7 and alcohols 8,9 have shown that the deuterium QCP depends in a sensitive way on the concentration and the temperature. The QCP, Q , is the product of the nuclear electric quadrupole moment, eQ, and the electric field gradient ͑EFG͒ at the nucleus, eq, that is,…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical studies of hydrogen bonding in neat, liquid formamide

Ludwig¹,

Weinhold²,

Farrar³

1995

The Journal of Chemical Physics

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Quadrupole coupling parameters ͑QCPs͒, Q , for nitrogen, oxygen, the carbonyl deuteron, and both amide deuterons in neat, liquid formamide were measured via NMR relaxation time experiments as a function of temperature. At room temperature the experimental values obtained for nitrogen, oxygen, carbonyl deuteron, and cis and trans amide deuteron were 2. 84, 9.18, 0.170, 0.280, and 0.233 MHz, respectively. These parameters and also the quadrupole coupling asymmetry parameters, Q , were calculated using standard ab initio self-consistent field methods at the 6-31G* level for eight different clusters of formamide molecules. The cluster sizes varied from one to six molecules and include linear and cyclic structures. At room temperature the theoretical calculations indicate that the dominant ͑95%͒ species is a six-membered ring of formamide molecules involving hydrogen bonding between the trans amide deuteron and the oxygen. This ring shows strong cooperative effects. The ab initio values obtained for the QCPs and the asymmetry parameters of this ring are 2.94 MHz and 0.394 for the nitrogen, 9.28 MHz and 0.402 for the oxygen, 0.182 MHz and 0.038 for the carbonyl deuteron, 0.285 MHz and 0.147 for the cis, and 0.221 MHz and 0.223 for the trans deuteron, respectively. These results are in excellent agreement with the experimental NMR results; both show clearly that primarily the trans amide proton is involved in hydrogen bonding. Other structural data from x-ray, electron, and neutron diffraction, low-frequency Raman and far-IR spectra are consistent with the conclusion that cyclic hexamers are the dominant species of liquid formamide under standard state conditions.

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Molecular Reorientation in Liquid Methanol

Abstract: Oxygen-17 enriched methanol CD

Cited by 51 publications

References 0 publications

Composition dependence of thermodynamic, dynamic and dielectric properties of water–methanol model mixtures. Molecular dynamics simulation results with the OPLS-AA model for methanol

Composition dependence of thermodynamic, dynamic and dielectric properties of water–methanol model mixtures. Molecular dynamics simulation results with the OPLS-AA model for methanol

Oxygen-17-induced proton relaxation rates for alcohols and alcohol solutions

Experimental and theoretical studies of hydrogen bonding in neat, liquid formamide

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