Hydration free energy difference of acetone, acetamide, and urea

2008 ◽  
Vol 129 (16) ◽  
pp. 164501 ◽  
Author(s):  
Pál Jedlovszky ◽  
Abdenacer Idrissi
Keyword(s):  
Free Energy ◽  
Energy Difference ◽  
Hydration Free Energy ◽  
Free Energy Difference

Hydrogen bonding solvent effect on the basicity of primary amines CH3NH2, C2H5NH2, and CF3CH2NH2

1981 ◽  
Vol 59 (1) ◽  
pp. 151-155 ◽  
Author(s):  
Yan K. Lau ◽  
P. Kebarle
Keyword(s):  
Free Energy ◽  
Energy Difference ◽  
Ion Source ◽  
Primary Amines ◽  
Hydration Free Energy ◽  
Ion Hydration ◽  
Free Energy Difference ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Good Agreement

The equilibria RNH3+(H2O)n−1 + H2O = RNH3+(H2O)n were measured for R = CH3, C2H5, and CF3CH2 from n = 1 to n = 3 with a pulsed electron beam high ion source pressure mass spectrometer. The proton and hydrate transfer equilibria CH3NH3+(H2O)n + C2H5NH2 = CH3NH2 + C2H5NH3+(H2O)n were measured for n = 0 to n = 3. These data allow the evaluation of ΔH0 and ΔG0 for the reactions: R0NH3+(H2O)n + RNH3+ = R0NH3+ + RNH3+(H2O)n. ΔH0 = δΔH00,n(RNH3+), ΔG = δΔG00,n(RNH3+). These data are compared with δΔE0,3 (STO-3G) evaluated by Hehre and Taft. In general good agreement is observed at n = 3. The δΔH00,3(RNH3+) ≈ δΔE0,3(RNH3+) are also found close to the ion hydration free energy difference in aqueous solutions.

Conformational analysis of 1,4-disubstituted cyclohexanes. III. trans-1,4-Di(trifluoroacetoxy)cyclohexane

1969 ◽  
Vol 47 (3) ◽  
pp. 429-431 ◽  
Author(s):  
Gordon Wood ◽  
E. P. Woo ◽  
M. H. Miskow
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Conformational Analysis ◽  
Integration Method ◽  
Standard Free Energy ◽  
Energy Difference ◽  
Free Energy Difference ◽  
Conformational Free Energy

By the low temperature nuclear magnetic resonance integration method the standard free energy difference between the diequatorial and the diaxial forms of 1-H,4-H-trans-1,4-di(trifluoroacetoxy)-cyclohexane-d8 was found to be 77 ± 5 cal/mole. The conformational free energy (−ΔG0) of the trifluoroacetoxy group in the monosubstituted cyclohexane was 485 ± 4 cal/mole at the same temperature. The non-additivity of the −ΔG0 values is discussed in terms of transannular electrostatic interaction.

A comprehensive computational examination of transannular Diels–Alder reactions of unsubstituted C14 trienes — Barriers, template effects, and the Curtin–Hammett principle

2001 ◽  
Vol 79 (8) ◽  
pp. 1284-1292 ◽  
Author(s):  
Saul Wolfe ◽  
Anthony V Buckley ◽  
Noham Weinberg
Keyword(s):  
Free Energy ◽  
Energy Difference ◽  
Diels Alder ◽  
Molecular Orbital Calculations ◽  
Free Energy Difference ◽  
Molecular Mechanics Calculations ◽  
Geometrical Isomers ◽  
Free Energy Of Activation ◽  
Transition Structures ◽  
Cyclic Compounds

A combination of MM3-level molecular mechanics calculations and PM3-level semiempirical molecular orbital calculations has been employed, in conjunction with an algorithm for the comprehensive conformational analysis of cyclic compounds, to obtain 1202 unique 1,3,9-cyclotetradecatriene conformations, distributed over the six possible geometrical isomers, and 70 unique transannular Diels–Alder transition structures leading to the six possible stereoisomeric tricyclic olefins. A kinetic analysis that takes into account all minima of a given geometrical isomer and all transition structures leading to the same tricyclic product leads to a free energy of activation that is almost the same as the free energy difference between the lowest minimum and the lowest transition structure (the Curtin–Hammett principle). A substantial template effect, mainly entropic in origin, is found when the transannular reactions are compared to the Diels–Alder reactions of the cognate 2,4-hexatrienes with the 2-butenes. Although the cyclization of the trans-cis-trans triene favours the cis-anti-cis over the trans-anti-trans product by more than 20 kcal mol–1, the situation is reversed in the acyclic reaction. A cyclic triene that can cyclize directly to a trans-anti-trans tricycle can therefore be proposed.Key words: molecular models, Deslongchamps, Takahashi, trans-anti-trans tricycle, MM3, PM3, transition states.

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