scholarly journals Theoretical Investigation of Solvation Effects on the Tautomerism of Maleic Hydrazide

2012 ◽  
Vol 9 (1) ◽  
pp. 107-112 ◽  
Author(s):  
Meisam Shabanian ◽  
Hassan Moghanian ◽  
Mohsen Hajibeygi ◽  
Azin Mohamadi
Keyword(s):  
Gas Phase ◽  
Polar Solvent ◽  
Maleic Hydrazide ◽  
Aprotic Solvent ◽  
Dipole Moments ◽  
Structural Data ◽  
Protic Solvent ◽  
Polar Aprotic Solvent ◽  
Pcm Model ◽  
Nbo Charges

A DFT study is used to calculate structural data of tautomers of maleic hydrazide (MH) in the gas phase and selected solvents such as benzene (non-polar solvent), tetrahydrofuran (polar aprotic solvent) and methanol (protic solvent), dimethyl sulfoxide (polar aprotic solvent) and water (protic solvent) using PCM model. All tautomers are optimized at the B3LYP/6−31++G(d,p). The results show that the tautomer MH2except in methanol is more stable than the other tautomers but in methanol MH5(Diol) is more stable. In addition, stability of the tautomers in deferent solvents shows interesting results. Variation of dipole moments and NBO charges on atoms in the solvents were studied.

Investigation of Solvent-Dependent Catalytic Behavior of a Hydrophobic Guest Artificial Glutathione Peroxidase

2014 ◽  
Vol 940 ◽  
pp. 20-23
Author(s):  
Yan Zhen Yin ◽  
Shu Fei Jiao ◽  
Xiong Gan ◽  
Zhong Feng Shi ◽  
Xiao Xi Hu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Glutathione Peroxidase ◽  
Aprotic Solvent ◽  
Protic Solvent ◽  
Catalytic Behavior ◽  
Polar Aprotic Solvent ◽  
Catalytic Rate

The investigation of the catalytic behavior of a hydrophobic guest artificial glutathione peroxidase (GPx) (ADA-Te-ADA) was carried out employing H2O2 and 3-carboxyl-4-nitrobenzenethiolas (TNB) as substrates. The relation between the catalytic rate of ADA-Te-ADA and the property of solvent used in the determination of catalytic activity was revealed. Typically, the co-solvents including ethanol, DMSO, DMF and CH3CN were employed in the determination of catalytic rates. It indicated that ADA-Te-ADA exhibited the typical solvent-dependent catalytic behavior. Especially, the higher catalytic rate was observed when polar protic solvent (ethanol) was used compared with other co-solvents. It suggested that polar protic solvent was the appropriate co-solvent for the assay of catalytic activity of hydrophobic artificial GPx. Additionally, the strong polarity of polar aprotic solvent plays an important role in the enhancement of GPx catalytic activity. This study bodes well for the understanding of the catalytic behavior of hydrophobic guest artificial GPx.

Studies on tautomerism in the triazoline dione

2011 ◽  
Vol 89 (11) ◽  
pp. 1387-1395 ◽  
Author(s):  
Alireza Salimi Beni ◽  
Zeinab Dalirnasab ◽  
Abbas Teimouri ◽  
Alireza Najafi Chermahini
Keyword(s):  
Water Molecule ◽  
Proton Transfer ◽  
Gas Phase ◽  
Transfer Reaction ◽  
Dipole Moments ◽  
Chemical Properties ◽  
Proton Transfer Reaction ◽  
Basis Sets ◽  
Dft Methods ◽  
Pcm Model

The chemical properties of the triazoline dione have been extensively studied. The relative stability of three tautomers in the gas phase and solution (using PCM model) are evaluated using HF and DFT methods and compared with MP2 level using different basis sets. The results of the calculations indicate that 4H-1,2,4-triazole-3,5-dione (K form) is more stable in the gas phase than in solution. In addition, the transition states of proton transfer reaction is calculated. The vibrational frequencies and corresponding normal mode assignments of 4H-1,2,4-triazole-3,5-dione and 5-hydroxy-3H-1,2,4-triazol-3-one (E1 form) are also theoretically examined. In addition, the variation of dipole moments and charges on atoms with change of solvent is studied. Specific solvent effects with addition of one molecule of water near the electrophilic centers of three tautomers and the transition state of proton transfer assisted by a water molecule was investigated. Aggregation with water molecules does not change the order of stability of isomers, but proton transfer reaction assisted by a water molecule needs less energy than the intramolecular process.

Solvent-Dependent Catalytic Behavior of Hydrophobic Guest Artificial Glutathione Peroxidase Determined Using H2O2 and 4-Nitrobenzenethiol as Substrates

2014 ◽  
Vol 926-930 ◽  
pp. 230-233
Author(s):  
Shu Fei Jiao ◽  
Yan Zhen Yin ◽  
Xiong Gan ◽  
Xiao Xi Hu ◽  
Zhong Feng Shi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Glutathione Peroxidase ◽  
Aprotic Solvent ◽  
Protic Solvent ◽  
Catalytic Behavior ◽  
Polar Aprotic Solvent ◽  
Catalytic Rate

Using H2O2 and 4-nitrobenzenethiol as substrates, the catalytic behavior of a hydrophobic guest artificial glutathione peroxidase (GPx) (ADA-Te-ADA) was detailed investigated. The relation between the catalytic rate of ADA-Te-ADA and the property of solvent used in the determination of catalytic rate was revealed. Typically, Ethanol, DMSO, DMF and CH3CN were selected as the co-solvents in the determination of catalytic rates. It indicated that ADA-Te-ADA exhibited the typical solvent-dependent catalytic behavior. Especially, the higher catalytic rate was observed when polar protic solvent (ethanol) was used compared with other co-solvents. It suggested that polar protic solvent was the appropriate co-solvent for the assay of catalytic activity of hydrophobic artificial GPx. Additionally, the strong polarity of polar aprotic solvent plays an important role in the enhancement of GPx catalytic activity. This study bodes well for the understanding of the catalytic behavior of hydrophobic guest artificial GPx .

THEORETICAL CALCULATION OF pKb VALUES FOR ANILINES AND SULFONAMIDE DRUGS IN AQUEOUS SOLUTION

2012 ◽  
Vol 11 (02) ◽  
pp. 283-295 ◽  
Author(s):  
BAHRAM GHALAMI-CHOOBAR ◽  
ALI GHIAMI-SHOMAMI ◽  
PARIA NIKPARSA
Keyword(s):  
Gas Phase ◽  
Continuum Model ◽  
Correlation Equation ◽  
Polarizable Continuum Model ◽  
Free Energies ◽  
Pcm Model ◽  
Solvation Models ◽  
Polarizable Continuum ◽  
Better Than ◽  
Good Agreement

In this work, calculations of p K b values have been performed for aniline and its substituted derivatives and sulfonamide drugs by using Gaussian 98 software package. Gas-phase energies were calculated with HF /6-31 G ** and B3LYP /6-31 G ** levels of theory. Free energies of solvation have been computed using the polarizable continuum model (PCM), conductor-like polarizable continuum model (CPCM) and the integral equation formalism-polarizable continuum model (IEFPCM) at the same levels which have been used for geometry determination in the gas-phase. The results show that the calculated p K b values using the B3LYP /6-31 G ** are better than those using the corresponding HF /6-31 G **. At first, the correlation equation was found to determine the p K b values of the investigated anilines. Then, this correlation equation was used to calculate the p K b values of the sulfonamide drugs. The results obtained indicate that the PCM model is a suitable solvation model for calculating p K b values in comparison to the other solvation models. For the investigated compounds a good agreement between the experimental and the calculated p K b values was also observed.

Cyclic trimers of phosphinic acids in polar aprotic solvent: symmetry, chirality and H/D isotope effects on NMR chemical shifts

2018 ◽  
Vol 20 (7) ◽  
pp. 4901-4910 ◽  
Author(s):  
V. V. Mulloyarova ◽  
I. S. Giba ◽  
M. A. Kostin ◽  
G. S. Denisov ◽  
I. G. Shenderovich ◽  
...  
Keyword(s):  
Aprotic Solvent ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Nmr Chemical Shifts ◽  
Polar Aprotic Solvent ◽  
Phosphinic Acids ◽  
Proton Chemical Shifts ◽  
Bonded Complexes ◽  
Hydrogen Bonded

By using NMR in liquefied gases, the stoichiometry of hydrogen-bonded complexes is determined via H/D isotope effects on proton chemical shifts.

Probing Intramolecular Interaction of Stereoisomers Using Computational Spectroscopy

2020 ◽  
Vol 73 (8) ◽  
pp. 813
Author(s):  
Feng Wang ◽  
Shawkat Islam ◽  
Frederick Backler
Keyword(s):  
Hydrogen Bonding ◽  
Binding Energy ◽  
Gas Phase ◽  
Intramolecular Interaction ◽  
Dipole Moments ◽  
Energy Difference ◽  
Binding Energies ◽  
Intramolecular Interactions ◽  
Computational Spectroscopy ◽  
Ionic States

Several model stereoisomers such as ferrocene (Fc), methoxyphenol, and furfural conformers are discussed. It was discovered that the Fc IR spectroscopic band(s) below 500cm−1 serve as fingerprints for eclipsed (splitting 17 (471–488)cm−1) and staggered Fc (splitting is ~2 (459–461)cm−1) in the gas phase. It is revealed that in the gas phase the dominance of the eclipsed Fc (D5h) at very low temperatures changes to a mixture of both eclipsed and staggered Fc when the temperature increases. However, in solvents such as CCl4, eclipsed Fc dominates at room temperature (300K) due to the additional solvation energy. Intramolecular interactions of organic model compounds such as methoxyphenols (guaiacol (GUA) and mequinol (MEQ)) and furfural, ionization energies such as the carbon 1s (core C1s), as well as valence binding energy spectra serve this purpose well. Hydrogen bonding alters the C1s binding energies of the methoxy carbon (C(7)) of anti-syn and anti-gauche conformers of GUA to 292.65 and 291.91eV, respectively. The trans and cis MEQ conformers, on the other hand, are nearly energy degenerate, whereas their dipole moments are significantly different: 2.66 Debye for cis and 0.63 Debye for trans-MEQ. Moreover, it is found that rotation around the Cring–OH and the Cring–OCH3 bonds differ in energy barrier height by ~0.50 kcal⋅mol−1. The Dyson orbital momentum profiles of the most different ionic states, 25a′ (0.35eV) and 3a′ (−0.33eV), between cis and trans-MEQ in outer valence space (which is measurable using electron momentum spectroscopy (EMS)), exhibit quantitative differences. Finally, the molecular switch from trans and cis-furfural engages with a small energy difference of 0.74 kcal mol−1, however, at the calculated C(3)(–H⋅⋅⋅O=C) site the C1s binding energy difference is 0.105eV (2.42 kcal mol−1) and the NMR chemical shift of the same carbon site is also significant; 7.58ppm from cis-furfural without hydrogen bonding.

Gas-Phase NMR Measurements, Absolute Shielding Scales, and Magnetic Dipole Moments of29Si and73Ge Nuclei

2006 ◽  
Vol 110 (40) ◽  
pp. 11462-11466 ◽  
Author(s):  
W. Makulski ◽  
K. Jackowski ◽  
A. Antušek ◽  
M. Jaszuński
Keyword(s):  
Gas Phase ◽  
Magnetic Dipole ◽  
Dipole Moments

Experimental Determination of Dipole Moments of Some Benzamide Derivatives

1998 ◽  
Vol 53 (8) ◽  
pp. 684-688
Author(s):  
J. Heidt ◽  
J. R. Heidt ◽  
M. Raciniewskab
Keyword(s):  
Excited State ◽  
Experimental Determination ◽  
Gas Phase ◽  
Electronic Absorption ◽  
Dipole Moments ◽  
Absorption Bands ◽  
Excited State Dipole Moments ◽  
Benzamide Derivatives

Abstract The excited state dipole moments of some benzamide derivatives are determined. The method of solvent induced shifts of electronic absorption bands in comparison with their positions in the gas phase is used. Some regular trends revealed in the obtained data are discussed. The present results are compared with those available in the literature.

Solvolysis of sulphonyl halides. VIII. Reaction of methane and ethane sulphony1 chlorides with methanol, ethanol, and mixed solvent systems

1971 ◽  
Vol 24 (4) ◽  
pp. 713 ◽  
Author(s):  
R Foon ◽  
AN Hambly
Keyword(s):  
Carbon Tetrachloride ◽  
Room Temperature ◽  
Reaction Rate ◽  
Mixed Solvent ◽  
Aprotic Solvent ◽  
Excess Enthalpies ◽  
Initial State ◽  
Polar Aprotic Solvent ◽  
Rate Of Reaction ◽  
Solvent Systems

At room temperature methanesulphonyl chloride reacts more rapidly than ethanesulphonyl chloride in solvolysis by ethanol. Their rates of reaction with methanol are approximately equal while ethanesulphonyl chloride is the more reactive in hydrolysis. The enthalpies and entropies of activation have been determined for the solvolysis of ethanesulphonyl chloride in mixtures of ethanol with benzene, carbon tetrachloride, or 2,2,4-trimethylpentane. A comparison of the excess enthalpies and entropies of mixing in the formation of these solvents with the corresponding parameters for reaction shows that the effects on reaction rate are not due merely to the modification of the initial state of the system. The effect of the polar aprotic solvent nitrobenzene on the rate of reaction with methanol is attributed to an increase in the nucleophilic tendency of the methanol rather than to solvation of the reactive centre in the transition state.

Sign in / Sign up

Export Citation Format

Share Document