The butane condensed matter conformational problem

Weber, Adrian C. J.; Lange, C.A. de; Meerts, W. Leo; Burnell, E. Elliott

doi:10.1016/j.cplett.2010.07.014

Cited by 13 publications

(18 citation statements)

References 29 publications

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“…So far these ranges were decided on by applying the above-mentioned phenomenological models and by incorporating a simple rotational isomeric state (RIS) approach for conformational changes. As is shown, e.g., in experimental studies of n-butane 26 and n-pentane, 21 the ranges for the dipolar couplings obtained in this way provide an adequate starting point for the evolutionary analysis procedure.…”

Section: 11mentioning

confidence: 99%

Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

Weber

Pizzirusso

Muccioli

et al. 2012

The Journal of Chemical Physics

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The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from these simulations are compared with the NMR experimental ones. The simulation predictions provide an excellent starting point for analysis of the experimental NMR spectra using the covariance matrix adaptation evolutionary strategy. This shows both the power of atomistic simulations for aiding spectral analysis and the success of atomistic molecular dynamics in modeling these anisotropic systems.

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Section: 11mentioning

confidence: 99%

Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

Weber

Pizzirusso

Muccioli

et al. 2012

The Journal of Chemical Physics

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“…More recently it was found that the effect calculated for a liquid-crystal condensed phase on the conformational statistics of n-butane was largely dependent on the model chosen to describe the orientational potential [21]. The RIS approximation was avoided by use of an intramolecular potential calculated by GAUSSIAN 03 (and will be used in the present study) and it was found that the CI (2k) model (defined by Eqs.…”

mentioning

confidence: 98%

“…For this purpose we choose to analyze results in terms of both the CCd and CI (2k) models. These models (and their variants) predicted very different conformer probabilities in the earlier paper [21], and hence they can be taken to be representative of differences caused by the choice of model.…”

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confidence: 99%

Conformational statistics of n-butane in the condensed phase and the effects of temperature

Weber

Burnell

2011

Chemical Physics Letters

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“…33 Another way of treating the n-pentane conformational problem is by using a continuous intramolecular potential, U iso int, n (φ 1 , φ 2 ); this treatment (using continuous probability distributions) was recently used in NMR studies on n-butane. 25,26,34,35 To do this for n-pentane, the internal energy was calculated in 15 • increments of φ 1 and φ 2 while keeping all other structural parameters fixed to those of the major conformer that exists at the bottom of the local (or global in the case of tt) energy well (see Figure 3 for potential energy plotted as a function of φ 1 and φ 2 ). These energy wells, calculated for the n-pentane molecule isolated in the gas phase, are affected by the environment in the anisotropic liquid phase in which the solute is dissolved.…”

Section: Methodsmentioning

confidence: 99%

A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

Burnell

Weber

Dong

et al. 2015

The Journal of Chemical Physics

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The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche + gauche + , pp, and gauche + gauche − , pm), the isotropic trans-gauche energy difference E tg and its temperature coefficient E ′ tg are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche + gauche − conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase. C 2015 AIP Publishing LLC. [http://dx

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The butane condensed matter conformational problem

Cited by 13 publications

References 29 publications

Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

Conformational statistics of n-butane in the condensed phase and the effects of temperature

A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

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