The problem of the structure of liquid aliphatic nitriles

Горбунова, Т В; Batalin, G. I.

doi:10.1007/bf00746654

Cited by 3 publications

(4 citation statements)

References 11 publications

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“…Despite the relatively simple structure of an acetonitrile molecule, the organization of liquid acetonitrile exhibits fascinating behavior. Given the substantial dipole moment of this molecule (3.92 D), acetonitrile has some propensity for dipole pairing in the bulk. , However, at a silica surface, acetonitrile takes on a remarkably different organization. Because acetonitrile can accept a hydrogen bond, there is a layer of molecules whose cyano groups point toward the silica surface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature on the Organization of Acetonitrile at the Silica/Liquid Interface

2017

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Liquid acetonitrile at a silica surface is known to organize in a manner that, in some respects, resembles a supported lipid bilayer. Here we use broadband vibrational sum-frequency generation (VSFG) spectroscopy to study how this organization depends on temperature. We find that VSFG spectra in the methyl-stretching region of the spectrum decrease in magnitude and shift to the blue for all polarization combinations (SSP, SPS, and PPP) as the temperature is raised from 25 to 60 °C. The observed decrease in intensity with increasing temperature is unexpected and suggests that the dynamics of the second sublayer of acetonitrile molecules plays an important role in the spectral behavior of this system. We propose that the decrease in intensity with increasing temperature arises largely from the more static first sublayer becoming more disordered. This picture is supported by the observed blue shift at high temperature, which is consistent with faster reorientation-induced spectral diffusion. The rapid dynamics and average orientation of the second sublayer are biased by the first sublayer, but this bias is not influenced substantially by increasing the temperature.

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Section: Introductionmentioning

confidence: 99%

Effect of Temperature on the Organization of Acetonitrile at the Silica/Liquid Interface

2017

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“…This is connected with that the most substantial restructurings of the structure of the water-acetone mixtures occur at < 0.25 m.f. [29,30].…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Thermodynamics of Re-Solvation of Cadmium Ions in Water-Acetone Solvents

Chankina

Parfenyuk

2005

Russ J Electrochem

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On the basis of a method of differences of Volta-potentials at 298.15 K the real primary effect of an environment of cadmium ions and the real Gibbs energy for the transport of ë d 2+ out of water into a wateracetone solvent ( åÂ 2 ëé ) are determined. The surface potential at the nonaqueous solvent/gas phase interface is obtained. This quantity is taken into account when calculating chemical thermodynamic characteristics for cadmium ions and the surface potential at the gas phase/acetone interface = -0.337 V. Thermodynamic characteristics of the over-solvation of a II-I electrolyte with those for a I-I electrolyte are compared. Key words : voltaic difference of potentials, primary effect of an environment, Gibbs energy for transport ∆χ H 2 O S ∆χ Me 2 O

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“…4−6 Although the ordering in liquid acetonitrile can be described largely in terms of repulsive interactions, 7 there is also a propensity for dipole pairing. 4,5 In longer-chain nitriles, the increasing importance of nonpolar/nonpolar interactions with decreasing temperature leads to changes in ordering 4 that are reflected in dynamics. 6 The balance of interactions in nitriles can be disrupted by a cosolvent.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Nitriles are some of the most widely used solvents in chemistry. − The nature of nitriles gives these liquids the ability to solvate a broad range of species, and the interplay between polar/polar and nonpolar/nonpolar interactions leads to interesting intermolecular ordering. − Although the ordering in liquid acetonitrile can be described largely in terms of repulsive interactions, there is also a propensity for dipole pairing. , In longer-chain nitriles, the increasing importance of nonpolar/nonpolar interactions with decreasing temperature leads to changes in ordering that are reflected in dynamics …”

Section: Introductionmentioning

confidence: 99%

Nitriles at Silica Interfaces Resemble Supported Lipid Bilayers

Berne

Fourkas²,

Walker

et al. 2016

Acc. Chem. Res.

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Nitriles are important solvents not just for bulk reactions but also for interfacial processes such as separations, heterogeneous catalysis, and electrochemistry. Although nitriles have a polar end and a lipophilic end, the cyano group is not hydrophilic enough for these substances to be thought of as prototypical amphiphiles. This picture is now changing, as research is revealing that at a silica surface nitriles can organize into structures that, in many ways, resemble lipid bilayers. This unexpected organization may be a key component of unique interfacial behavior of nitriles that make them the solvents of choice for so many applications. The first hints of this lipid-bilayer-like (LBL) organization of nitriles at silica interfaces came from optical Kerr effect (OKE) experiments on liquid acetonitrile confined in the pores of sol-gel glasses. The orientational dynamics revealed by OKE spectroscopy suggested that the confined liquid is composed of a relatively immobile sublayer of molecules that accept hydrogen bonds from the surface silanol groups and an interdigitated, antiparallel layer that is capable of exchanging into the centers of the pores. This picture of acetonitrile has been borne out by molecular dynamics simulations and vibrational sum-frequency generation (VSFG) experiments. Remarkably, these simulations further indicate that the LBL organization is repeated with increasing disorder at least 20 Å into the liquid from a flat silica surface. Simulations and VSFG and OKE experiments indicate that extending the alkyl chain to an ethyl group leads to the formation of even more tightly packed LBL organization featuring entangled alkyl tails. When the alkyl portion of the molecule is a bulky t-butyl group, packing constraints prevent well-ordered LBL organization of the liquid. In each case, the surface-induced organization of the liquid is reflected in its interfacial dynamics. Acetonitrile/water mixtures are favored solvent systems for separations technologies such as hydrophilic interaction chromatography. Simulations had suggested that although a monolayer of water partitions to the silica surface in such mixtures, acetonitrile tends to associate with this monolayer. VSFG experiments reveal that, even at high water mole fractions, patches of well-ordered acetonitrile bilayers remain at the silica surface. Due to its ability to donate and accept hydrogen bonds, methanol also partitions to a silica surface in acetonitrile/methanol mixtures and can serve to take the place of acetonitrile in the sublayer closest to the surface. These studies reveal that liquid nitriles can exhibit an unexpected wealth of new organizational and dynamic behaviors at silica surfaces, and presumably at the surfaces of other chemically important materials as well. This behavior cannot be predicted from the bulk organization of these liquids. Our new understanding of the interfacial behavior of these liquids will have important implications for optimizing a wide range of chemical processes in nitrile solvents.

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The problem of the structure of liquid aliphatic nitriles

Cited by 3 publications

References 11 publications

Effect of Temperature on the Organization of Acetonitrile at the Silica/Liquid Interface

Effect of Temperature on the Organization of Acetonitrile at the Silica/Liquid Interface

Thermodynamics of Re-Solvation of Cadmium Ions in Water-Acetone Solvents

Nitriles at Silica Interfaces Resemble Supported Lipid Bilayers

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