Polar stacking of molecules in liquid chloroform

Shephard, Jacob J.; Soper, A. K.; Callear, Samantha K.; Imberti, Silvia; Evans, John S. O.; Salzmann, Christoph G.

doi:10.1039/c4cc09235j

Cited by 26 publications

(69 citation statements)

References 28 publications

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“…The smaller decrease of CC environments compared to AA environments is in line with chloroform's tendency for selfaggregation into polar chains 49 which seems to be preserved to at least some extent in the azeotrope (cf. Figure 4).…”

Section: Comparison Of the Local Environments In The Two Different Azmentioning

confidence: 63%

“…By comparing the structural model of the acetone-chloroform azeotrope with pure liquid chloroform, 49 the previously observed unusual shift of the CC-HC stretching mode towards higher wavenumbers upon addition of chloroform to liquids with proton acceptor character 29, 60-62 can now be better understood. This observation, which is the opposite of what might be expected for C-H···O hydrogen bond formation, is attributed to the disturbance of chloroform's selfassociation in the pure liquid.…”

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

“…This effect may also explain the 'non-specific' dilution shift in the 1 H-NMR spectra of chloroform-acetone mixtures. 26 Figure 4 shows a comparison of the percentages of chloroform molecules in chains with collinear dipole moments in the EPSR models of pure liquid chloroform 49 and the acetonechloroform azeotrope. The greater number of chloroform molecules with a chain length of 1 (i.e.…”

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

“…[45][46][47] The approximate interaction distances from EPSR models of the pure liquids are also included. 48,49 Focussing on the OA-HC hydrogen bonding interaction, an important reference state is the 1:1 acetone-chloroform co-crystal formed at 150 K. In the cocrystal, the shortest OA-HC distance is 2.41 Å. 45 The maximum in the OA-HC gij(r) at 2.76 Å indicates that the interaction distance in the azeotrope is significantly longer.…”

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

“…no chloroformchloroform associations) and lower number of chloroform molecules with chain length > 1 in the azeotrope than in pure chloroform shows that the self-association of chloroform is significantly disrupted in the azeotrope. Chains analysis applied to the EPSR models of pure liquid chloroform 49 (green) and the acetone-chloroform azeotrope (red). Molecules were considered to be in a chain of chloroform molecules with collinear alignment of dipole moments for rH···C < 4.2 Å and H···C-H > 150°.…”

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

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Microstructures of negative and positive azeotropes

Shephard

Callear

Imberti

et al. 2016

Phys. Chem. Chem. Phys.

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Azeotropes famously impose fundamental restrictions on distillation processes, yet their special thermodynamic properties make them highly desirable for a diverse range of industrial and technological applications. Using neutron diffraction, we investigate the structures of two prototypical azeotropes, the negative acetone-chloroform and the positive benzenemethanol azeotrope. C-H···O hydrogen bonding is the dominating interaction in the negative azeotrope but C-Cl···O halogen bonding contributes as well. Hydrogen-bonded chains of methanol molecules, which are on average longer than in pure methanol, are the defining structural feature of the positive azeotrope illustrating the fundamentally different local mixing in the two kinds of azeotropes. The emerging trend for both azeotropes is that the more volatile components experience the more pronounced structural changes in their local environments as the azeotropes form. The mixing of the acetonechloroform azeotrope is essentially random above 20 Å where the running Kirkwood-Buff integrals of our structural model converge closely to the ones expected from thermodynamic data. The benzene-methanol azeotrope on the other hand displays extended methanol-rich regions and consequently, the running Kirkwood-Buff integrals oscillate up to at least 60 Å. Our study provides first insights into the microstructures of azeotropes and a direct link with their thermodynamic properties. Ultimately, this will provide a route for creating tailored molecular environments in azeotropes to improve and fine-tune their performances.

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Section: Comparison Of the Local Environments In The Two Different Azmentioning

confidence: 63%

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

Section: Local Structure Of the Acetone-chloroform Azeotropementioning

confidence: 99%

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Microstructures of negative and positive azeotropes

Shephard

Callear

Imberti

et al. 2016

Phys. Chem. Chem. Phys.

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Design of Fluoro‐Free Surfaces Super‐Repellent to Low‐Surface‐Tension Liquids

et al. 2023

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Super‐liquid‐repellent surfaces feature high liquid contact angles and low sliding angles find key applications in anti‐fouling and self‐cleaning. While repellency for water is easily achieved with hydrocarbon functionalities, repellency for many low‐surface‐tension liquids (down to 30 mN m−1) still requires perfluoroalkyls (a persistent environmental pollutant and bioaccumulation hazard). Here, the scalable room‐temperature synthesis of stochastic nanoparticle surfaces with fluoro‐free moieties is investigated. Silicone (dimethyl and monomethyl) and hydrocarbon surface chemistries are benchmarked against perfluoroalkyls, assessed using model low‐surface‐tension liquids (ethanol–water mixtures). It is discovered that both hydrocarbon‐ and dimethyl‐silicone‐based functionalization can achieve super‐liquid‐repellency down to 40–41 mN m−1 and 32–33 mN m−1, respectively (vs 27–32 mN m−1 for perfluoroalkyls). The dimethyl silicone variant demonstrates superior fluoro‐free liquid repellency likely due to its denser dimethyl molecular configuration. It is shown that perfluoroalkyls are not necessary for many real‐world scenarios requiring super‐liquid‐repellency. Effective super‐repellency of different surface chemistries against different liquids can be adequately predicted using empirically verified phase diagrams. These findings encourage a liquid‐centric design, i.e., tailoring surfaces for target liquid properties. Herein, key guidelines are provided for achieving functional yet sustainably designed super‐liquid‐repellency.

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Host–Guest Exchange of Viologen Guests in Porphyrin Cage Compounds as Studied by Selective Exchange Spectroscopy (1D EXSY) NMR

Swartjes¹,

White²,

Lammertink³

et al. 2020

Angewandte Chemie

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Dynamics in complexes of porphyrin cage compounds and viologen-derived guest molecules are investigated by selective exchange NMR spectroscopy (1D EXSY). Exchange rates were found to be independent of excess guest concentration, revealing a dissociative exchange mechanism, which is accompanied by negative activation entropies, indicating significant reorganization of the host-guest complex during dissociation. Nonsymmetric viologen guests with bulky head groups had more unidirectional binding and slower exchange rates than guests with less-bulky head groups. Thermodynamic and kinetic studies revealed that the exchange process is primarily driven by the thermodynamics of binding and that guest binding can be influenced by introducing steric and electronic groups on the host . Exchange studies with guests bearing a polymer chain revealed that both slippage and full dissociation takes place and the rate constants for both processes were determined. The slippage rate constant revealed that for smaller guests exchange takes place nearly exclusively under thermodynamic control.

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Polar stacking of molecules in liquid chloroform

Cited by 26 publications

References 28 publications

Microstructures of negative and positive azeotropes

Microstructures of negative and positive azeotropes

Design of Fluoro‐Free Surfaces Super‐Repellent to Low‐Surface‐Tension Liquids

Host–Guest Exchange of Viologen Guests in Porphyrin Cage Compounds as Studied by Selective Exchange Spectroscopy (1D EXSY) NMR

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