High Pressure 13C NMR Study of the Motional Dynamics of Liquid Bis(2-ethylhexyl) Phthalate

Kim, Yoo Joong; Jonáš, J.

doi:10.1021/j100018a005

Cited by 8 publications

(32 citation statements)

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“…The dipole−dipole relaxation rate, may be obtained from the standard relationship between the overall T 1 and NOE measurements: 24 The reorientation correlation time obtained in this manner is an average assuming isotropic reorientation of the C−H vector. This correlation time may be related to a rotational diffusion coefficient by assuming that each CH 2 bead is roughly spherical and rotates randomly: From the temperature dependence of rotational diffusion coefficients at fixed viscosity, one can determine effective rotational activation energies. Table lists these energies for 1-decanol in CO 2 at fluid viscosity of 0.09 cP, along with some of the previous activation energies.…”

Section: Resultsmentioning

confidence: 99%

CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

et al. 1997

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A sapphire high-pressure NMR cell, capable of independently controlling sample pressure, temperature, and concentration, is used to measure 13 C spin-lattice relaxation times for carbons 1, 5, and 9 of 1-decanol in dense carbon dioxide at pressure between 80 and 200 atm. These NMR experiments, carried out along four isotherms between 288 and 348 K, provide relaxation data for 1-decanol in liquid and supercritical fluid CO 2 . The nuclear spin-lattice relaxation mechanisms for carbons 1, 5, and 9 of 1-decanol as well as for the carbon nucleus in carbon dioxide of this mixture are discussed. The relaxation data are analyzed using a modified Stokes-Einstein-Debye equation, together with an AK model, that postulates the formation of CO 2 clusters with the 1-decanol molecule in CO 2 -decanol mixture at supercritical and near-critical liquid densities. Such CO 2 cluster formation with methanol molecules was also detected in earlier relaxation measurements in CO 2 -methanol mixtures at the comparable densities. Possible solvent clustering gradients along the aliphatic chain in 1-decanol in dense CO 2 are also suggested.

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Section: Resultsmentioning

confidence: 99%

CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

et al. 1997

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“…The experimental relaxation data for the individual carbon nuclei were analyzed in terms of a model assuming a Cole−Davidson distribution of relaxation times. The detailed method of analysis has been described previously . In short, the theoretical expressions for T 1 and NOE, eqs 1 and 2, with J (ω) replaced by the spectral density function of the Cole−Davidson distribution model, eq 5, were fitted to the experimental data to yield a set of optimum parameters.…”

Section: Resultsmentioning

confidence: 99%

“…Information on the motional behavior of these molecules can be obtained from the interpretation of the optimized parameters of the Cole−Davidson distribution model. As discussed in the previous paper, τ 0 * and B , among three parameters, are considered to describe the motional behavior as a whole (the overall motion), and β contains information about the motional details of individual carbon nuclei from which the internal motion of the molecule can be estimated. The correlation time for the overall motion described by τ 0 * and B via eq 7 are in fact the limiting correlation time of the Cole−Davidson model which represents the slowest process of the molecular motion that rotationally averages a particular C−H relaxation vector.…”

Section: Resultsmentioning

confidence: 99%

“…Carbon-13 NMR relaxation measurements were performed at 45.2 or 100.6 MHz. The home-built NMR spectrometer system with a 4.2 T magnet (for the relaxation measurements at 45.2 MHz) as well as the techniques of relaxation measurements have been described in the previous report …”

Section: Methodsmentioning

confidence: 99%

“…Among them, the theoretical model assuming a Cole−Davidson distribution of correlation times proved to be the most suitable for describing the dynamic structure of the complex phthalate liquid. This model has successfully described the reorientational motions in many complex, viscous fluids. ,,− In the Cole−Davidson distribution model, , the spectral density function assumes a distribution of isotropic reorientational correlation times given by where the normalized probability density of the distribution, g (τ), takes the form β is the distribution width and may assume a value from 0 to 1. In the case where β = 1, only one correlation time exists, and consequently the spectral density function reduces to that of the isotropic reorientational model.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of Complex Phthalate Liquids. 1. Structural Effects of Molecular Framework

Kim

Jonáš

1998

J. Phys. Chem. A

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The motional behavior of complex phthalates and structurally related liquids has been investigated in order to study the structural effect of molecular framework on the macroscopic and microscopic dynamic properties. 13C NMR spin−lattice relaxation times and nuclear Overhauser enhancements (NOE) of individual carbon nuclei of bis(2-ethylhexyl) cyclohexane-1,2-dicarboxylate (DEHHP), bis(2-ethylhexyl) isophthalate (DEHIP), bis(2-ethylhexyl) terephthalate (DEHTP), and tris(2-ethylhexyl) trimellitate (TOTM) have been measured as a function of temperature from −40 to 90 °C. Individual 13C peaks were unambiguously assigned by using 2D hydrogen−carbon chemical shift correlation spectra. In addition, the density and viscosity of these compounds as a function of temperature have been measured. The results were also compared with those of 2-ethylhexyl benzoate (EHB), 2-ethylhexyl cyclohexanecarboxylate (EHC), and bis(2-ethylhexyl) phthalate (DEHP), complex liquids studied earlier in our laboratory. Both the macroscopic and microscopic dynamic properties were significantly affected by the structure of the molecular framework. The conjugation between a phenyl ring and carboxyl groups was found to make the structural framework stiffer and resulted in an enhanced viscosity. The 13C NMR relaxation data were interpreted in terms of a theoretical model assuming a Cole−Davidson distribution of correlation times. The internal motions of the common 2-ethylhexyl side chains were found to be independent of the nature of the molecular framework of the compounds. The parameter β in the Cole−Davidson model, representing the distribution width of the involved correlation times of the molecular motions, contained useful information on the detailed motional features of individual carbon nuclei. The β values for the rigid phenyl ring carbons reflected the reorientational anisotropy resulting from the molecular shape of the structural framework and could be successfully correlated with the parameter κ introduced by McClung and Kivelson in the modified Stokes−Einstein−Debye (SED) equation. On the other hand, the β values for the flexible cyclohexane ring carbons were affected by both the internal motion of the cyclohexane ring and the anisotropy of the molecular reorientation.

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Supercritical Fluids

Taylor¹,

Jacobson²

2007

Encyclopedia of Magnetic Resonance

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High Pressure 13C NMR Study of the Motional Dynamics of Liquid Bis(2-ethylhexyl) Phthalate

Cited by 8 publications

References 3 publications

CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

Dynamics of Complex Phthalate Liquids. 1. Structural Effects of Molecular Framework

Supercritical Fluids

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High Pressure 13C NMR Study of the Motional Dynamics of Liquid Bis(2-ethylhexyl) Phthalate

Cited by 8 publications

References 3 publications

CO2 Clustering of 1-Decanol and Methanol in Supercritical Fluids by 13C Nuclear Spin−Lattice Relaxation

CO2 Clustering of 1-Decanol and Methanol in Supercritical Fluids by 13C Nuclear Spin−Lattice Relaxation

Dynamics of Complex Phthalate Liquids. 1. Structural Effects of Molecular Framework

Supercritical Fluids

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CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation

CO₂ Clustering of 1-Decanol and Methanol in Supercritical Fluids by ¹³C Nuclear Spin−Lattice Relaxation