Investigation of direct polar conjugation in thioanisoles and anisoles by the dipole moment method

Borovikov, Yu. Ya.; Топчий, В. А.

doi:10.1007/bf00526055

Cited by 8 publications

(13 citation statements)

References 4 publications

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“…As shown in ref , the FEM calculations readily reproduce both the Sauerbrey equation and the Gordon−Kanazawa result, , with an error of <0.1%. The film resonance in liquids is reproduced within 1%.…”

Section: Modelingsupporting

confidence: 61%

Dissipation in Films of Adsorbed Nanospheres Studied by Quartz Crystal Microbalance (QCM)

2009

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The quartz crystal microbalance (QCM) has become a popular method to study the formation of surface-confined films that consist of discrete biomolecular objects--such as proteins, phospholipid vesicles, virus particles--in liquids. The quantitative interpretation of QCM data--frequency and bandwidth (or, equivalently, dissipation) shifts--obtained with such films is limited by the lack of understanding of the energy dissipation mechanisms that operate in these films as they are sheared at megahertz frequencies during the QCM experiment. Here, we investigate dissipation mechanisms in such films experimentally and by finite-element method (FEM) calculations. Experimentally, we study the adsorption of globular proteins and virus particles to surfaces with various attachment geometries: direct adsorption to the surface, attachment via multiple anchors, or attachment via a single anchor. We find that the extent of dissipation caused by the film and the evolution of dissipation as a function of surface coverage is not dependent on the internal properties of these particles but rather on the geometry of their attachment to the surface. FEM calculations reproduce the experimentally observed behavior of the dissipation. In particular, a transient maximum in dissipation that is observed experimentally is reproduced by the FEM calculations, provided that the contact zone between the sphere and the surface is narrow and sufficiently soft. Both a small-angle rotation of the sphere in the flow field of the background fluid (rocking) and a small-amplitude slippage (sliding) contribute to the dissipation. At high coverage, lateral hydrodynamic interactions between neighboring spheres counteract these modes of dissipation, which results in a maximum in dissipation at intermediate adsorption times. These results highlight that, in many scenarios of biomolecular adsorption, the dissipation is not primarily determined by the adsorbate itself, but rather by the link by which it is bound to the substrate.

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Section: Modelingsupporting

confidence: 61%

Dissipation in Films of Adsorbed Nanospheres Studied by Quartz Crystal Microbalance (QCM)

2009

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“…A study of the initial rate of the azidation of silyl ether 2e as a function of the electronics of the nitro cocatalyst (100 mol %) in benzene shows that electron-rich nitrobenzenes have a much larger promoting effect than electron-poor analogues (Figure ). This trend is opposite to the expected outcome if small changes in dielectric constant due to the additive were responsible for the faster rates since p -methoxynitrobenzene (ε = 27.5) is less polar than nitrobenzene (ε = 36.1) . The method of initial rates was used to determine the order of the individual components for the reaction of 2e in benzene.…”

mentioning

confidence: 90%

“…In contrast, all five other solvents tested that contained a nitro group led to rapid progression of the reaction after 1 h, even though in some cases their dielectric constants are much lower than nitromethane (Table S1). Azidation could even be carried out in “unreactive” solvents when nitro compounds were employed as additives. To our delight, 50 mol % p -nitroanisole was an effective cocatalyst for the azidation of alcohol 1e in benzene, giving 65% isolated yield after 24 h compared to <5% in the absence of cocatalyst, eq . …”

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confidence: 99%

Nitro-Assisted Brønsted Acid Catalysis: Application to a Challenging Catalytic Azidation

et al. 2015

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A cocatalytic effect of nitro compounds is described for the B(C6F5)3·H2O catalyzed azidation of tertiary aliphatic alcohols, enabling catalyst turnover for the first time and with a broad range of substrates. Kinetic investigations into this surprising effect reveal that nitro compounds induce a switch from first order concentration dependence in Brønsted acid to second order concentration dependence in Brønsted acid and second order dependence in the nitro compounds. Kinetic, electronic, and spectroscopic evidence suggests that higher order hydrogen-bonded aggregates of nitro compounds and acids are the kinetically competent Brønsted acid catalysts. Specific weak H-bond accepting additives may offer a new general approach to accelerating Brønsted acid catalysis in solution.

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“…Its potential applications go much beyond microgravimetry . Acoustic sensing of viscosity is now routine. , Effects of viscoelasticity are well understood for planar layer systems. − As the samples have become more and more complex, lateral heterogeneity has turned into one of the biggest hurdles in quantitative modeling. Many biologically motivated investigations concern adsorbed objects, which are spatially separated.…”

mentioning

confidence: 99%

“…While modeling of heterogeneous samples might appear to be demanding, the general approach is rather clear, when basing the analysis on the small-load approximation (see eq below). On a fundamental level, the frequency shift, Δ f , is proportional to the ratio of (average) stress and speed at the resonator surface. , The well-known formalism of QCM data analysis for planar layer systems (including the Sauerbrey equation and the Gordon-Kanazawa result , ) follows straightforwardly from the small-load approximation, if the stress is calculated with theory of planar acoustic multilayers. Before elaborating on the extension of the formalism to heterogeneous loads, we comment on the existing approaches dealing with heterogeneity.…”

mentioning

confidence: 99%

Effect of Sample Heterogeneity on the Interpretation of QCM(-D) Data: Comparison of Combined Quartz Crystal Microbalance/Atomic Force Microscopy Measurements with Finite Element Method Modeling

et al. 2008

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A quartz crystal microbalance was integrated into an AFM in order to monitor the adsorption of biomolecules to the resonator surface with both atomic force microscopy and microgravimetry. The comparison between the two techniques allows the fractional coverage of the surface, theta, to be correlated with the frequency shift of the resonator, deltaf. The adsorbed material was ferritin, which is a spherical protein with a diameter of approximately 12 nm. Even ata coverage below 50%, the protein layer exhibits Sauerbrey-like behavior, meaning that the magnitude in the frequency shift [deltaf] much exceeds the shift in bandwidth and that the normalized frequency shift, deltaf/n (n the overtone order), is similar on the different overtones. The relation between coverage and frequency shift was found to be nonlinear. In order to model this situation, we performed finite element method calculations based on the incompressible Navier-Stokes equation. The comparison between the model and the experiment suggests that the deformation of the protein upon adsorption is small. For low coverage, the volume of the trapped solvent exceeds the volume of the adsorbate itself. The ratio of the two decreases with increasing coverage. This is the cause of the experimentally observed nonlinear relationship between the surface coverage and frequency shift. Comparing frequency shifts at different overtones, one finds that deltaf/n slightly decreases with overtone order. Such a behavior is typically attributed to softness. The model shows that, for the adsorbed spheres, this apparent softness arises through a rocking motion of the spheres at the surface instead of the shear deformation. Also, there is a hydrodynamic contribution (related to roughness) to the overtone dependence of deltaf/n.

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Investigation of direct polar conjugation in thioanisoles and anisoles by the dipole moment method

Cited by 8 publications

References 4 publications

Dissipation in Films of Adsorbed Nanospheres Studied by Quartz Crystal Microbalance (QCM)

Dissipation in Films of Adsorbed Nanospheres Studied by Quartz Crystal Microbalance (QCM)

Nitro-Assisted Brønsted Acid Catalysis: Application to a Challenging Catalytic Azidation

Effect of Sample Heterogeneity on the Interpretation of QCM(-D) Data: Comparison of Combined Quartz Crystal Microbalance/Atomic Force Microscopy Measurements with Finite Element Method Modeling

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