Temperature dependent dielectric relaxation study of tetrahydrofuran in methanol and ethanol at microwave frequency using time domain technique

Chaudhari, Ajay; Khirade, P. W.; Singh, Raghubar; Helambe, S. N.; Narain, Narendra; Mehrotra, S. C.

doi:10.1016/s0167-7322(99)00102-6

Cited by 45 publications

(21 citation statements)

References 8 publications

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“…This assignment is supported by the fact that a 10 ps solvation time scale is too slow to ascribe to simple dielectric relaxation. 57,58 The relatively slow solvation observed is explained by the fact that 3-fold coordinated Na 0 , which is formed from occasional fluctuations in our 1 ns equilibrium simulation, has a lifetime of several picoseconds (see Supporting Information). In an upcoming paper, we will present the full details of how relatively simple changes in solvent coordination number explain the full ultrafast transient spectroscopy of this system.…”

Section: Changes In the Electronicmentioning

confidence: 92%

Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran

2010

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With no internal vibrational or rotational degrees of freedom, atomic solutes serve as the simplest possible probe of a condensed-phase environment's influence on solute electronic structure. Of the various atomic species that can be formed in solution, the quasi-one-electron alkali atoms in ether solvents have been the most widely studied experimentally, primarily due to the convenient location of their absorption spectra at visible wavelengths. The nature of solvated alkali atoms, however, remains controversial: the consensus view is that solvated alkali atoms exist as (Na + , e -) tight-contact pairs (TCPs), species in which the alkali valence electron is significantly displaced from the alkali nucleus and confined primarily by the first solvent shell. Thus, to shed light on the nature of alkali atoms in solution and to further our understanding of condensedphase effects on solutes' electronic structure, we have performed mixed quantum/classical molecular dynamics simulations of sodium atoms in liquid tetrahydrofuran (Na 0 /THF). Our interest in this particular system stems from recent pump-probe experiments in our group, which found that the rate at which this species is solvated depends on how it was created (Science 2008, 321, 1817); in other words, the solvation dynamics of this system do not obey linear response. Our simulations reproduce the experimental spectroscopy of this system and clearly indicate that neutral Na atoms exist as (Na + , e -) TCPs in solution. We find that the driving force for the displacement of sodium's valence electron is the formation of a tight solvation shell around the partially exposed Na + . On average, four THF oxygens coordinate the cation end of the TCP; however, we also observe fluctuations to other solvent coordination numbers. Furthermore, we find that species with different solvent coordination numbers have unique absorption spectra and that interconversion between species with different solvent coordination numbers requires surmounting a free energy barrier of several k B T. Taken together, our results suggest that the Na 0 /THF species with different solvent coordination numbers may be viewed as chemically distinct. Thus, we can explain the kinetics of Na TCP formation as being dictated by changes in the Na + solvent coordination number, and we can understand the dependence on initial conditions seen in the solvation dynamics of this system as resulting from the fact that the important solvent coordinate involves the motion of only a few molecules in the first solvation shell.

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Section: Changes In the Electronicmentioning

confidence: 92%

Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran

2010

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“…The dependence of HDH rate on solvent can be again represented in terms of Eq. (16), with e THF ¼7, v THF ¼ 75 cm 3 mol À1 and drawing on reference data (Chaudhari et al, 1999;Nayak et al, 2004) for the excess properties (see Eqs. (12)-(13) in Section 3.4).…”

Section: Hdh Of Chlorobenzenesmentioning

confidence: 99%

Solvent effects in the catalytic hydrotreament of haloaromatics over Pd/Al2O3 in water+organic mixtures

Gómez‐Quero

Díaz

Cárdenas‐Lizana

et al. 2010

Chemical Engineering Science

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“…The loss tangent, which is defined by '' tan / ' ef δ ε ε = , is an 3 important parameter in describing the dielectric response of materials. 1,2,6 For example, the penetration depth (D p) , the distance at which the amplitude of the electrical field is damped to 1/e = 0.369 of its initial value at the surface of the material, is related to the loss tangent by 6 1/ 2 2 2 1 tan 1 ' Over recent years the dielectric properties of alcohols and their mixtures have been extensively studied [7][8][9][10][11][12][13][14][15][16] and the dielectric properties of pure solvents have become widely available in the literature. [17][18] However, data on the dielectric behavior of vegetables oils, animal fats, or even their mixtures with primary alcohols, are scarce.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Behavior of Reaction Mixture during Acid-Catalyzed Transesterification Reactions in Biodiesel Production

et al. 2016

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Information on the behavior of the dielectric properties of electrolytic solutions, such as reaction mixtures, during acid-catalyzed transesterification reactions in biodiesel production is essential in the design of processes involving microwave-heating technology. The influence of the acid catalyst on the dielectric parameters during the methanolysis and ethanolysis of crude Brazil nut oil was investigated employing H 2 SO 4 , H 3 PO 4 , ClSO 3 H and CH 3 SO 3 H as the catalysts. Refined Soybean, refined babassu and waste Brazil nut oils were used to study the dielectric behavior during the transesterification reaction catalyzed by H 2 SO 4 . Measurements were taken using a vector network analyzer with an open-ended coaxial probe (300 MHz -13 GHz). The dielectric properties of the reaction mixtures during the transesterification reaction were frequency-dependent and varied markedly with the conversion to biodiesel. The catalyst used significantly affected the dielectric properties, contributing to the high values (0.14-0.40) for the loss tangent of the reaction mixtures. The high content of free fatty acids and water in the oils also contributed considerably to the dielectric behavior during the transesterification reaction.

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Temperature dependent dielectric relaxation study of tetrahydrofuran in methanol and ethanol at microwave frequency using time domain technique

Cited by 45 publications

References 8 publications

Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran

Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran

Solvent effects in the catalytic hydrotreament of haloaromatics over Pd/Al2O3 in water+organic mixtures

Dielectric Behavior of Reaction Mixture during Acid-Catalyzed Transesterification Reactions in Biodiesel Production

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Temperature dependent dielectric relaxation study of tetrahydrofuran in methanol and ethanol at microwave frequency using time domain technique

Cited by 45 publications

References 8 publications

Nature of Sodium Atoms/(Na+, e−) Contact Pairs in Liquid Tetrahydrofuran

Nature of Sodium Atoms/(Na+, e−) Contact Pairs in Liquid Tetrahydrofuran

Solvent effects in the catalytic hydrotreament of haloaromatics over Pd/Al2O3 in water+organic mixtures

Dielectric Behavior of Reaction Mixture during Acid-Catalyzed Transesterification Reactions in Biodiesel Production

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Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran

Nature of Sodium Atoms/(Na⁺, e⁻) Contact Pairs in Liquid Tetrahydrofuran