Solvent effects on strong charge-transfer complexes. IV. Trimethylamine and sulfur dioxide in the vapor phase

Grundnes, Just; Christian, Sherril D.; Cheam, Venghuot; Farnham, Sutton B.

doi:10.1021/ja00730a003

Cited by 11 publications

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References 2 publications

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“…From literature data [5,13,14], the equilibrium constant or association constant is seriously influenced by the nature of the solvent employed. Equilibrium constant is a measure of stability of the CTC formed.…”

Section: Discussionmentioning

confidence: 99%

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Onah¹,

Odeiani²,

Ajima³

2013

OJPC

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Purpose: Tenofovir disoproxil fumarate (TEN) and emtricitabine (EMT) are both second generation ant-retroviral drugs used in the “treatment” of HIV/AIDS. The aim of this study is to establish the physic-chemical properties of their reaction with chloranilic acid in different solvent systems and to justify the chemical basis for simultaneous quantitative determination of these drugs in their combined formulation. Method: TEN and EMT were individually isolated from their single formulations and purified by chromatography to obtain secondary standard. Purity of the isolates were tested for by comparison with literature values. Stock solution of chloranilic acid (CA) [3.0 × 10^﹣³ M] was prepared in the following solvents of different polarities: ethanol, acetonitrile, ethylacetate, chloroform and hexane. Equal volumes of CA and TEN [3.0 × 10^﹣² M] and EMT [3.0 × 10^﹣² M] dissolved in different solvents were mixed whereby colored products were observed. Absorption maxima were determined. Calibration curves were generated and validated. Quantitative simultaneous determination of TEN and EMT was determined by standard protocol. Stoichiometric relationships between the drugs and CA were established. Equilibrium constants were determined at different temperatures from which the Gibb’s free energies were calculated. Arrhenius equation was used to calculate the enthalpy, entropy was similarly calculated. Results: Absorption maxima of CA in different solvents are as follows: Ethanol 310 nm; Acetonitrile 330 nm; Ethyl acetate 340 nm; Chloroform 350 nm and hexane 310 nm. The complex of CA and TEN in the different solvents are: Alcohol 525 nm, Acetonitrile 500 nm; Ethyl acetate 505 nm; Chloroform 510 nm and hexane 515 nm. For EMT complex absorption maxima are: Alcohol 510 nm; Acetonitrile 515 nm’ Ethyl acetate 520 nm’ Chloroform 505 nm and hexane 530 nm. Simultaneous quantitative recovery values for TEN are: Ethanol; 97.89% ± 1.21; Acetonitrile 101.17 V 1.51%; Ethyl acetate 96.55% ± 0.71%; Chloroform 99.11% ± 0.34% and hexane 98.03% ± 0.15%. For EMT the values are also: Ethanol: 98.92% ± 1.45%; Acetonitrile 100.471 ± 13; Ethyl acetate 97.06% ± 0.87%; Chloroform 99.31% ± 0.94% and Hexane 99.97% ± 1.63%. Stoichiometry of complexation showed a 1:1 ratio for both drugs. Equilibrium constants for TEN were highest in acetonitrile and least for Ethanol while for EMT, equilibrium constant was least for acetonitrile and highest in chloroform. Gibb’s free energy for TEN was least in ethanol and highest in acetonitrile. Gibb’s free energy for EMT was least in acetonitrile and highest in chloroform. Enthalpy for TEN was least in chloroform and highest in hexane. Similarly, the enthalpy for EMT was highest in chloroform and lowest in hexane. Conclusion: These results shows that solvent polarity influence charge transfer complexes in a non consistent fashion. The structure of the donor might have contributed to thermodynamics of complexation since orbital over...

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Section: Discussionmentioning

confidence: 99%

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Onah¹,

Odeiani²,

Ajima³

2013

OJPC

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“…Figure 3. Structures, bond lengths (in pm), and symmetry of the complexes SOCl 2 ·NH 3 (7), SOCl 2 ·NMe 3 (8), and SONH·NH 3 (9) in the gas phase. The bond lengths of 7 and 8 in a polar continuum of dielectric constant ε = 40 are given in parentheses.…”

Section: Adducts Of Soclmentioning

confidence: 99%

“…[5] Subsequently, this compound has been extensively studied by X-ray crystallography of single crystals, [6,7] microwave spectroscopy in the vapor phase, [7] UV/Vis spectroscopy in solution, [8] vapor density measurements, [9] and ab initio MO calculations. [3,[10][11][12] The most recent and most sophisticated theoretical study applying the MP2/6-31G* level of theory predicted S-N distances of 235.9 pm for 2 and 270.7 pm for SO 2 ·2NMe 3 (2a).…”

Section: Introductionmentioning

confidence: 99%

“…However, neither spectra nor structural determinations or theoretical calculations are known for these complexes. To elucidate the structures, thermodynamics, and bonding of these interesting adducts and of a number of related species we have carried out extensive quantum chemical calculations at the G3X(MP2) level of theory not only for 1, 1a, 2, and 2a, but also for the first time for the related complexes S 2 O·NH 3 (3), S 2 O·NMe 3 (4), S 3 ·NH 3 (5), S 3 ·NMe 3 (6), SOCl 2 ·NH 3 (7), SOCl 2 ·NMe 3 (8), and SONH·NH 3 (9). The Gibbs energies of formation from the separated components have also been calculated for the species 1-8 for the first time, both in the vapor phase and in a polar medium, to predict the thermodynamic stability of these compounds under standard and nonstandard conditions.…”

Section: Introductionmentioning

confidence: 99%

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Charge‐Transfer Complexes between the Sulfur Molecules SO₂, S₂O, S₃, SONH, and SOCl₂ and the Amine Donors NH₃ and NMe₃ – A Theoretical Study

Steudel

2007

Eur J Inorg Chem

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The formation of adducts between the acceptor molecules SO2, S2O, S3, and SOCl2 and the donor molecules ammonia and trimethylamine has been studied by high‐level G3X(MP2) theory, in most cases for the first time. Minimum energy structures with a 1:1 composition and with sulfur–nitrogen bonds have been located for all complexes. The thermodynamic properties, vibrational spectra, and atomic charges of these molecules have been calculated. Of the 10 investigated complexes, only SO2·NMe3 (2) and S2O·NMe3 (4) are predicted to be thermodynamically stable in the gas phase under standard conditions (ΔG°298 < 0). However, all adducts except S3·NH3 (5), SOCl2·NH3 (7), and SOCl2·NMe3 (8) are stable thermodynamically at 77 K. In a polar continuum with a dielectric constant (ϵ) of 40, complexes 2, 4, and S3·NMe3 (6) are stable even at 25 °C. However, if the adducts are formed in the polar continuum from the gaseous components, all adducts except S3·NH3 are formed not only exothermally but also exergonically. Complexes 2, 4, and 8 are the only species known in the solid state so far. The charge transfer from donor to acceptor in the various complexes in the gas phase ranges from 0.08 to 0.39 electrostatic units and correlates inversely with the S–N bond length, which ranges from 198 to 295 pm. In general, the charge transfer weakens the bonds within the acceptor molecule, which therefore may be considered to become activated. The formation of thionyl imide (SONH) from SOCl2 and NH3 is exergonic in the gas phase and the interaction between SONH and NH3 is very weak. In the case of SO2, the 1:2 complexes SO2·2NH3 (1a) and SO2·2NMe3 (2a), which contain two S–N bonds, are unstable with respect to their three‐component molecules both in the gas phase and in a polar medium at 25 °C, but they are stable in the polar phase with respect to the gaseous components.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

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Individual tyrosine side‐chain contributions to circular dichroism of ribonuclease

Woody

2003

Biopolymers

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Experimental and theoretical studies using site-directed mutants of ribonuclease A (RNase A) offer more extensive information on the tyrosine side-chain contributions to the circular dichroism (CD) of the enzyme. Bovine pancreatic RNase A has three exposed tyrosine residues (Tyr73, Tyr76, and Tyr115) and three buried tyrosine residues (Tyr25, Tyr92 and Tyr97). The difference CD spectra between the wild type and the mutants at pH 7.0 (Deltaepsilon(277,wt) - Deltaepsilon(277,mut)) show bands with more negative DeltaDeltaepsilon(277) values for Y73F and Y115F than those for Y25F and Y92F and bands with positive DeltaDeltaepsilon(277) values for Y76F and Y97F. The theoretical calculations are in good semiquantitative agreement for all the mutants. The pH difference spectrum (pH 11.3-7.0) for the wild type shows a negative band at 295 nm and an enhanced positive band at 245 nm. The three mutants at buried tyrosine sites and one mutant at an exposed tyrosine site (Y76F) exhibit pH-difference spectra that are similar to that of the wild type. In contrast, two mutants at exposed tyrosine sites (Y73F and Y115F) exhibit diminished 295-nm negative bands and, instead of positive bands at 245 nm, negative bands are observed. Our results indicate that Tyr73 and Tyr115, two of the exposed tyrosine residues, are the largest contributors to the 277- and 245-nm CD bands of RNaseA, but the buried tyrosine residues and the one remaining exposed residue also contribute to these bands. Disulfide contributions to the 277- and 240-nm bands and the peptide contribution to the 240-nm band are confirmed theoretically.

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Solvent effects on strong charge-transfer complexes. IV. Trimethylamine and sulfur dioxide in the vapor phase

Cited by 11 publications

References 2 publications

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Charge‐Transfer Complexes between the Sulfur Molecules SO₂, S₂O, S₃, SONH, and SOCl₂ and the Amine Donors NH₃ and NMe₃ – A Theoretical Study

Individual tyrosine side‐chain contributions to circular dichroism of ribonuclease

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Solvent effects on strong charge-transfer complexes. IV. Trimethylamine and sulfur dioxide in the vapor phase

Cited by 11 publications

References 2 publications

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Influence of Solvent Polarity on the Physio-Chemical Properties and Quantitative Determinations of Tenofovir Disoproxil and Emtricitabine with Chloranilic Acid as Complexing Agent

Charge‐Transfer Complexes between the Sulfur Molecules SO2, S2O, S3, SONH, and SOCl2 and the Amine Donors NH3 and NMe3 – A Theoretical Study

Individual tyrosine side‐chain contributions to circular dichroism of ribonuclease

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Charge‐Transfer Complexes between the Sulfur Molecules SO₂, S₂O, S₃, SONH, and SOCl₂ and the Amine Donors NH₃ and NMe₃ – A Theoretical Study