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1

Dynamics simulation studies of solvation effect on the trans-xylomollin conformation

Mahboub R.

International Letters of Chemistry, Physics and Astronomy

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2013

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Vol. 8, iss. 2

132-140

EN

The present work describes the solvation effect on the trans-xylomollin conformation. We have studied the trans-xylomollin conformations with the distance restraints using simulation calculations. Distance Restraint Molecular Dynamic (DR-MD) and Distance Restraint Langevin Dynamic (DR-LD) simulations of the trans-xylomollin were performed with an efficient program. The geometries, interaction energies, bonds, angles, and the Van der Waals (VDW) interactions were carried out in solution and gas phases. This comparative study shows that the trans-xylomollin acquires low total energy in solution using DR-MD method and stable conformation under the AMBER field. This molecule reaches its high stable conformation state in solution environment. The solvation effect is more important with DR-MD simulations. Our results are goods and in agreement with the used force field.

2

The Mechanism and Kinetics of the Reaction of ClONO2 with Cl-

Chi S. M., Wang N., Xu N., Xin W. Y., Xu S. C., Li G. B.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 9

1641-1654

EN

Three original three-dimensional Potential Energy Surfaces (PESes) of the reaction have been obtained by Density Functional Theory calculation using the 6-311+G(d) basis to prove an assumption that there action of ClONO2 + Cl- Ž NO3 - + Cl2 in a gas phase is built up of two simpler reactions: ClONO2 + Cl- Ž (O2NOClCl)- and (O2NOClCl)- Ž NO3 - + Cl2. The PESes indicate that the inter mediate compound (O2NOClCl)- called Potential Well Compound (PWC) is trapped by a potential energy well of -13.2 kcal/mol deep. The (O2NOClCl)- PWC in a gas phase is a stable compound at low temperatures and will be examined in the low-temperature in frared spectra. The decomposition of (O2NOClCl)- in a gas phase is dominated by its dynamic effects, and its kinetics is predicted in the present work. In heterogeneous chemistry how ever, the (O2NOClCl)- PWC can not be stable even at ~180 K, due to H2O solvation, leading to decomposition of the PWC. Solvation mechanism for the total reaction has been suggested in this paper.

3

Solwatacja inicjatora w polimeryzacji rodnikowej

Szafko J., Pabin-Szafko B.

Prace Naukowe Instytutu Technologii Organicznej i Tworzyw Sztucznych Politechniki Wrocławskiej. Konferencje

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2003

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Vol. 52, nr 25

232-235

PL

Określono początkową szybkość termicznego (333 K) rozpadu 2,2'-azoizobutyronitrylu (0,05 - 012 mol-dm-3) w N,N-dimetyloformamidzie, metakrylanie metylu i ich mieszaninach (0.25 i 0.5). Wyniki interpretowano wg mechanizmu klasycznego oraz modelu solwatacji inicjatora. W obu przypadkach stwierdzono rozpad 1-rzędu.

EN

The thermal decomposition (333 K) initial rate of AIBN (0.05-0.12 mol-dm-3) in DMF/methyl methacrylate mixtures of various compositions (xM=0, 0.25, 0.5 and 1.0) is studied. The results were interpreted by the classical mechanism and a model of initiator solvation by monomer and solvent. Eqs. (2) and (5) allowed to determinate the order x and m as equal to 1 for the whole system.

4

Micro liquid-liquid extraction of acetyl derivatives of phenols

Urbanczyk A., Staniewski J., Apostoluk W., Szymanowski J.

Chemia Analityczna

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2002

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Vol. 47, No. 5

669-679

EN

Micro liquid-liquid extraction of phenols acetyl derivatives from aqueous solution was studied and distribution coefficient was successfully correlated with solvent and solute property parameters. Toluene selected as a solvent for the extraction proved to be appropriate for the process. Extraction depended mainly on the hydrophobicity of phenol acetyl derivatives and the ionic strength of the aqueous solution. With the use of large volume on-column sample introduction technique it was possible to determine phenols at the level of 1 ug L(-1) both in model and environmental samples with a flame ionization detector.

PL

Zastosowano metodę mikroekstrakcję ciecz-ciecz do wydzielania fenoli z próbek wodnych. Fenole ekstrahowano w postaci pochodnych acetylowych, przeprowadzając derywatyzację bezpośrednio w próbce wodnej za pomocą bezwodnika kwasu octowego. Wyznaczono współczynniki podziału acetylowych pochodnych fenoli pomiędzy fazę wodną i organiczną, które z powodzeniem skorelowano z parametrami rozpuszczalników oraz badanych związków. Odpowiednim ekstrahentem do tego celu okazał się toluen. Ekstrakcja zależała głównie od hydrofobowości acetylowych pochodnych fenoli oraz siły jonowej roztworu wodnego. Dozowanie próbki o dużej objętości metodą on-column pozwoliło na oznaczanie fenoli na poziomie l ug L(-1), zarówno w przypadku modelowych próbek wodnych, jak i próbek środowiskowych, przy zastosowaniu detektora płomieniowo-jonizacyjnego.

5

Hydrogen bonded complexes of coumarin 153

Królicki R., Jarzęba W., Soroushian B., Lampre I., Mostafavi M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 4

435-449

EN

Detailed studies of the hydrogen-bonded complexes of coumarin 153 (C153) have been carried out. It has been shown that nonlinear shifts of the steady-state absorption and fluorescence spectra taken in toluene-methanol solvent mixtures are caused by the formation of hydrogen bonded complexes between C153 and methanol, while preferential solvation plays a minor role only. IR measurements confirmed the ability of C153 to form hydrogen-bonded complexes with methanol and phenol. The stoichiometry of the formed complexes and relevant equilibrium constants have been estimated. Femtosecond solvation dynamics measurements of C153 in the toluene-methanol mixture (xMeOH = 0.2) showed that the average solvation time is higher than that in the pure solvents indicating slower relaxation of methanol in the mixture. The slow component of solvation dynamics (ok 20ps) can be attributed to translational diffusion of methanol to the first solvation shell of C153 and to the relatively slow reorientational motion of methanol involved in formation of hydrogen bond with the excited C153.

6

Models of the Hydrophobic Attraction

Widom B.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 4

507-515

EN

Some recently proposed models of hydrophobic attraction, equivalent to the Ising model of ferromagnetism, are described and their properties reviewed. They are such that the accommodation of a hydrophobic solute in the solvent is energetically favorable but even more unfavorable entropically, which is believed to be the basic mechanism of hydrophobicity in water solution. The effective attraction between pairs of solute molecules as mediated by the solvent is calculated, as is the deviation from additivity in the interactions among three or more. The very low solubilities of the solutes in the model solvents are also calculated. In a different model, based on a phenomenological free energy leading to a closed-loop solubility curve in the temperature-composition plane, one finds the same very great increase in heat capacity on dissolving a hydrophobic solute as is found in experiment.

7

Solvation and proton transfer phenomena in phenol derivative-tertiary amine-aprotic solvent systems

Ilczyszyn M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 1

91-100

EN

Proton transfer (PT) equilibria inside hydrogen-bonded complexes of phe-nols (AH) with triethylamine and JV-methylpiperidine (B), A-H...B A - o -H-B+, dissolved in cooled (up to 113 K) aprotic solvents are analysed using H NMR results. Two categories of situations, depending on the acid and base initial concentrations, are considered: slower and faster PT for the Cg : CAg w 2 and Cg : CAu > 2 solutions, re-spectively. They are characterised by enthalpy and entropy of PT and interpreted as a result of relations between the proton transfer and solvation phenomena. In strongly cooled CB : CAH Ť 2 solutions the intra-complex proton motion is probably coupled to the motion of the solvating base molecule. This phenomenon is qualitatively described by the density function of the energy attraction between the bridging AHB proton and the solvating amine molecule. In the CB : CAH > 2 solutions this mechanism does not work probably and the hydrogen bonded ion-pairs are strongly solvated by the neighbour amine molecules.

8

The Solvation of Carbohydrates in Dimethylsusfoxide and Water

Berger S., Diaz M., Hawat Ch.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

193-197

EN

The solvation of sucrose and other carbohydrates in DMSO and water is probed by intermolecular NOE measurements. The NOE effects are interpreted in terms of specific binding of the solvent to certain sites of the molecules. It is shown that DMSO attaches to specific sites of the sucrose molecule, whereas for water such a clear differentiation cannot be proven.

9

Correlation Between temperature Coefficients of Ag+L Cryptate Stability Constant and of Ag/Ag+ Electrode Potential

Lewandowski A., Galiński M.

Polish Journal of Chemistry

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1999

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Vol. 73, nr 12

1987-1994

EN

The temperature coefficients, dlogK/dT, of the stability constants of Ag+ complexes with cryptands 221 and 222 were obtained directly from van't Hoff linear plots logK=a+bT-1 in 10 aprotic solvents: acetone, acetobitrile, propanenitrile, butyronitrile, benzonitrile.

10

Femtosecond internal conversion and solvation dynamics of the solvated electrons in neat water and aqueous solution

Laenen R., Assel M., Laubereau A.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 4

283-301

EN

Transient pump-probe spectroscopy of equilibrated solvated electrons is car-ried out in neat water and in an aqueolls NaCl solution (5.9 M) in the visible and near infrared using pulses of 100-170 fs duration and polarization resolution. Excitation is per-formed by a pump pulse at 620 nm in the blue wing of the electronic absorption band of the e- promoting electrons from the Is ground state to the highest of the 2p-substates. Transient bleaching is observed in a broad interval around the maximum of the band at 720 nm, accompanied by induced absorption at longer wavelengths. No holeburning features are observed within our experimental time resolution suggesting a time constant T1<80 fs for rapid solvent relaxation and/or population redistribution among the excited 2p-substates. The relaxation dynamics clearly involves a first intermediate that is strongly proposed to be a modified excited. state .p' and the lifetime of which is determined to be T2 = 190:= 40 fs. After 500 fs an isosbestic point develops in the transient spectrum that is related to a second intermediate that is assigned to a modified ground state s". A fur-ther time constant T = 0.9:=: 0.15 ps accounts for the final recovery of the population to the original ground state 1s. Evidence for stimulated emission in the probe absorption of the first intermediate allows its assignment as p' and suggests a distinct red shift of the transition p' ~ ground state to 760 nm, while the transient absorption band of electrons in the longer-lived s"-level is centered at 810 nm. The negligible net anisotropy < 0.01 of the probe absorption measured during and after the excitation process indicates that the observed distribution of solvent cavities of hydrated electrons is close to spherical symmetry. Comparison with similar observations for NaCl solution is also reported.

11

Deuterium isotope fractionation between ortho-alkyl substituted phenols and t-butylthiol in oxygen bases

Wawer A., Jelińska-Kazimierczuk M., Szydłowski J.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 3

618-626

EN

Equilibrium isotope effect in the exchange reaction of deuterium between phenol (P), 2-isopropylphenol (IPP), 2,6-diisopropylphenol (DIPP), 2,6-ditertbutyl phenol (DTBP) and tertbutylthiol (TBT) has been studied at 298 K. The fractionation factors (alpha) have been measured in cyclohexane and carbon tetrachloride solution and in a few oxygen bases: acetone, 1,4-dioxane, ethyl formate, ethyl ether, tetrahydrofurane, N,N-dimethylformamide, dimethylsulphoxide and hexamethylphosphoramide. Using chemical shifts of phenol OH protons, the thermodynamic parameters of complex formation with the oxygen bases have been determined. The experimental data show that ln alpha correlates with the formation enthalpy of the phenol-oxygen base complex in DIPP-TBT-base system but there is no simple correlation in IPP-TBT-base system. Futhermore it was found that in DTBT-TBT-base system ln alpha depends linearly on the basicity of the (solvent DN parameters). On the other hand, ln alpha correlates with acidic parameters of the solvents (AN) in IPP-TBT-base and P-TBT-base systems. All above correlations are explained by taking into account two competition processes: selfassociation of phenol molecules and their solvation by oxygen bases.