scholarly journals 2,6-Di-tert-butylpyridine: an unusually weak base in dimethylsulfoxide

1988 ◽  
Vol 66 (5) ◽  
pp. 1159-1162 ◽  
Author(s):  
Robert L. Benoit ◽  
Monique Fréchette ◽  
Diane Lefebvre
Keyword(s):  
Gas Phase ◽  
Partition Coefficients ◽  
Enthalpy Of Solution ◽  
Solvent Molecule ◽  
Ionization Constants ◽  
Enthalpies Of Solution ◽  
Weak Base ◽  
High Basicity ◽  
Transfer Parameters ◽  
Sterically Hindered

The ionization constants of the conjugate acids BH+ of pyridine, 2-picoline, 2,6-lutidine, and 2,6-di-tert-butylpyridine (DTBP) have been determined in Me2SO. The partition coefficients of the bases B between Me2SO and water, and the enthalpies of solution and protonation of B in Me2SO have also been obtained. In contrast to its high basicity in the gas phase, DTBP is an abnormally weak base in Me2SO (pK = 0.81). The factors responsible for this very low basicity are analyzed by considering correlations between the gas-phase, Me2SO, and aqueous basicities of B and by comparing the transfer parameters for B and BH+. The solvation of DTBP and DTBPH+ in Me2SO and in water differs. While the solvation of DTBP in Me2SO is normal, the enthalpy of solution of DTBPH+ in Me2SO is abnormally low and close to that of a cation whose solvation is nonspecific. This suggests a much reduced H-bonding between sterically hindered DTBPH+ and the large Me2SO solvent molecule.

Basicity of 1,8-bis(dimethylamino)naphthalene and 1,4-diazabicyclo[2.2.2]octane in water and dimethylsulfoxide

1987 ◽  
Vol 65 (5) ◽  
pp. 996-1001 ◽  
Author(s):  
Robert L. Benoit ◽  
Diane Lefebvre ◽  
Monique Fréchette
Keyword(s):  
Free Energy ◽  
Partition Coefficients ◽  
Enthalpy Of Solution ◽  
Ionization Constants ◽  
Base System ◽  
Proton Sponge ◽  
Acid Base ◽  
Enthalpy Of Transfer ◽  
Calculated Enthalpy ◽  
Base Strength

The ionization constants of the conjugate acids [Formula: see text] of two bases widely used in synthesis, 1,8-bis(dimethylamino)naphthalene (PS), and 1,4-diazabicyclo[2.2.2]octane (DABCO), have been obtained in Me2SO and water. The partition coefficients of both bases B and their heats of solution and protonation have also been determined. The basicity of PS is dramatically reduced when passing from water to Me2SO while the basicity of DABCO remains unchanged, thus making DABCO the stronger base in Me2SO. The solvent effect on the base strength is analyzed in terms of free energy and enthalpy of transfer for B and H+, and for BH+, from water to Me2SO. The entropy-controlled much stronger solvation of PS in Me2SO is in line with that of aromatic compounds while the increased solvation of DABCO in water is due to H-bonding of its two nitrogens. PSH+, like H+, is better solvated by Me2SO while DABCOH+ does not show a definite preference for one solvent. The calculated enthalpy of solution of gaseous PSH+ is abnormally low when compared to that of DABCOH+ and of related BH+ ions, thus indicating that the proton of PSH+, in a strong intramolecular H-bond, does not normally H-bond to the solvent. Our results suggest that the proton sponge acid-base system could be used as a convenient reference to determine the free energy and enthalpy of transfer of H+ between solvents.

Gas-Phase Clustering of NO+ with H2S and H2O

2007 ◽  
Vol 72 (8) ◽  
pp. 1122-1138 ◽  
Author(s):  
Milan Uhlár ◽  
Ivan Černušák
Keyword(s):  
Hydrogen Bonds ◽  
Water Molecule ◽  
Gas Phase ◽  
Saddle Points ◽  
Solvent Molecule ◽  
Local Minima ◽  
Additional Water ◽  
Three Body ◽  
Rain Formation ◽  
Stable Structures

The complex NO+·H2S, which is assumed to be an intermediate in acid rain formation, exhibits thermodynamic stability of ∆Hº300 = -76 kJ mol-1, or ∆Gº300 = -47 kJ mol-1. Its further transformation via H-transfer is associated with rather high barriers. One of the conceivable routes to lower the energy of the transition state is the action of additional solvent molecule(s) that can mediate proton transfer. We have studied several NO+·H2S structures with one or two additional water molecule(s) and have found stable structures (local minima), intermediates and saddle points for the three-body NO+·H2S·H2O and four-body NO+·H2S·(H2O)2 clusters. The hydrogen bonds network in the four-body cluster plays a crucial role in its conversion to thionitrous acid.

Exploring chemistry features of favipiravir in octanol/water solutions

2021 ◽  
pp. 1-12
Author(s):  
Halimeh Rajabzadeh ◽  
Ayla Sharafat ◽  
Maryam Abbasi ◽  
Maryam Eslami Gharaati ◽  
Iraj Alipourfard
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Partition Coefficients ◽  
Density Functional ◽  
Water Solution ◽  
Peptide Group ◽  
Functional Theory ◽  
Water Solutions ◽  
Group Rotations ◽  
Heterocyclic Structure

Favipiravir (Fav) has become a well-known drug for medication of patients by appearance of COVID-19. Heterocyclic structure and connected peptide group could make changes for Fav yielding different features from those required features. Therefore, it is indeed a challenging task to prepare a Fav compound with specific features of desired function. In this work, existence of eight Fav structures by tautomeric formations and peptide group rotations were obtained using density functional theory (DFT) optimization calculations. Gas phase, octanol solution, and water solution were employed to show impact of solution on features of Fav besides obtaining partition coefficients (LogP) for Fav compounds. Significant impacts of solutions were seen on features of Fav with the obtained LogP order: Fav-7 >  Fav-8 >  Fav-4 >  Fav-3 >  Fav-2 >  Fav-5 >  Fav-1 >  Fav-6. As a consequence, internal changes yielded significant impacts on features of Fav affirming its carful medication of COVID-19 patients.

Theoretical study of the triangular bonding complex formed by carbon tetrabromide, a halide, and a solvent molecule in the gas phase

2012 ◽  
Vol 19 (1) ◽  
pp. 299-304 ◽  
Author(s):  
Xiao Ran Zhao ◽  
Yu Jie Wu ◽  
Juan Han ◽  
Qian Jin Shen ◽  
Wei Jun Jin
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Solvent Molecule ◽  
Carbon Tetrabromide

scholarly journals Correlation and Prediction of Partition Coefficients From the Gas Phase and from Water to Alkan-1-ols

2008 ◽  
Vol 47 (11) ◽  
pp. 3990-3995 ◽  
Author(s):  
Michael H. Abraham ◽  
Asadollah Nasezadeh ◽  
William E. Acree
Keyword(s):  
Gas Phase ◽  
Partition Coefficients

Correlation and prediction of partition coefficients for solute transfer to 1,2-dichloroethane from both water and from the gas phase

2008 ◽  
Vol 273 (1-2) ◽  
pp. 78-86 ◽  
Author(s):  
Laura M. Sprunger ◽  
Jennifer Gibbs ◽  
William E. Acree ◽  
Michael H. Abraham
Keyword(s):  
Gas Phase ◽  
Partition Coefficients ◽  
Solute Transfer
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