Nuclear magnetic resonance studies. XV. Conformational free energy of the formyl group

1967 ◽  
Vol 45 (23) ◽  
pp. 2955-2961 ◽  
Author(s):  
G. W. Buchanan ◽  
J. B. Stothers ◽  
Siu-Tzyy Wu
Keyword(s):  
Free Energy ◽  
Solvent Polarity ◽  
Formyl Group ◽  
Proton Spectroscopy ◽  
Kcal Mole ◽  
Magnetic Resonance Studies ◽  
Average Value ◽  
Cis And Trans ◽  
Line Positions ◽  
Conformational Free Energy

Proton spectroscopy has been employed to determine the conformational free energy (− ΔG0) of a formyl group bonded to a cyclohexane ring. The cis- and trans-4-t-butyl derivatives were used as models for the axial and equatorial formyl groups in cyclohexanecarboxaldehyde and 1-methylcyclohexanecarboxaldehyde. The wiggle-beat technique was used to determine the spectral line positions and separations because of the relatively small differences involved. The − ΔG0 values were found to be relatively insensitive to solvent polarity and concentration over the range 10–50 mole %. For 10 mole % solutions the average value of − ΔG0CHO was found to be 1.38 kcal/mole.

Interactions gauches et chemins réactionnels. Etudes conformationnelles d'hydroxyalkyl-4 cyclohexènes contraints

1981 ◽  
Vol 59 (5) ◽  
pp. 859-864
Author(s):  
Jeanine Bouteiller-Prati ◽  
Jean-Claude Bouteiller ◽  
Jean-Pierre Aycard
Keyword(s):  
Free Energy ◽  
Reaction Path ◽  
High Energy ◽  
Nmr Study ◽  
Conformational Equilibria ◽  
The Stability ◽  
Cis And Trans ◽  
Conformational Free Energy

From J and δ values determined by the nmr study of alcohols obtained by addition of CH3Li and LiAlH4 to the exocyclic carbonyl of cis and trans 3-alkyl 4-carbomethoxy (or acetyl) cyclohexenes (alkyl = H, CH3, C(CH3)3), we have deduced the conformational free energy values (ΔG0X) of the CH(CH3)OH and C(CH3)2OH substituents (0.62 and 2.08 kcal mol−1 respectively) as well as the values for some related conformational equilibria. For transtert-butyl derivatives the stability of the diaxial conformer agrees with a reaction path involving high energy conformers.

A(1,3) interaction and conformational energy of axial–axial 1,3-dimethyl interaction

1968 ◽  
Vol 46 (17) ◽  
pp. 2821-2825 ◽  
Author(s):  
Y. L. Chow ◽  
C. J. Colón ◽  
J. N. S. Tam
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Free Energy ◽  
Type Strain ◽  
Conformational Energy ◽  
Methyl Groups ◽  
Kcal Mole ◽  
Magnetic Resonance Studies ◽  
Free Energy Of Activation ◽  
C And N ◽  
Derivatives Of

A(1,3) type strain was demonstrated directly from the nuclear magnetic resonance studies of the acyl and nitroso derivatives of 2-methylpiperidine (2 series) and 2,6-cis-dimethylpiperidine (1 series). In these two series, the bulky 2-methyl groups are forced to assume the axial conformation due to a severe A(1,3) interaction in the equatorial conformation. The free energy of activation (ΔG*) for the internal rotation around the N—C and N—N bonds in 1a–1g was determined. The comparison of these (ΔG*) values with those of the corresponding derivatives of dimethylamine indicates the decreases are in the range of 3.6–4.7 kcal/mole which is in fair agreement with the conformational energy of 1,3-diaxial CH3/CH3 interaction. An argument was presented to show that this interaction energy corresponds to the decrease of ΔG* in 1a-1g.

Strongly hindered rotation in α,α,2,6-terrachlorotoluene. Stereospecific five-bond coupling. Hyperconjugative contributions to long-range sidechain-ring proton coupling constants

1968 ◽  
Vol 46 (12) ◽  
pp. 2187-2188 ◽  
Author(s):  
T. Schaefer ◽  
R. Schwenk ◽  
C. J. Macdonald ◽  
W. F. Reynolds
Keyword(s):  
Free Energy ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Proton Resonance ◽  
Kcal Mole ◽  
Hindered Rotation ◽  
Ring Proton ◽  
Meta Position ◽  
Proton Coupling ◽  
Free Energy Of Activation

At −40 °C the C—H bond of the dichloromethyl group of α,α,2,6-tetrachlorotoluene lies in the plane of the ring. The proton resonance spectrum demonstrates a stereospecific five-bond coupling between the C—H proton and the ring proton in the meta position. The coupling to the para proton is essentially zero as expected from a hyperconjugative mechanism. The free energy of activation of rotation of the dichloromethyl group is about 15 kcal/mole at 25 °C.

Nuclear magnetic resonance studies of cis- and trans-2,3-dimethylcycloalkanones

1972 ◽  
Vol 37 (15) ◽  
pp. 2425-2428 ◽  
Author(s):  
P. E. Pfeffer ◽  
S. F. Osman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Studies ◽  
Cis And Trans ◽  
Nuclear Magnetic

The Rotational Spectrum of Monothioformic Acid. I. cis-and trans-HC(:O)SH1,2

1976 ◽  
Vol 31 (5) ◽  
pp. 422-437
Author(s):  
William H. Hocking ◽  
Gisbert Winnewisser
Keyword(s):  
Frequency Region ◽  
Absorption Lines ◽  
Rotational Spectrum ◽  
Centrifugal Distortion ◽  
Astrophysical Interest ◽  
Rotational Spectra ◽  
Measured Line ◽  
Centrifugal Distortion Constants ◽  
Cis And Trans ◽  
Line Positions

Abstract The rotational spectra of the two abundant isomers of monothioformic acid, cis- and trans- HC(:O)SH, have been assigned in the frequency region 8 -250 GHz. Over 90 a-type transitions and over 60 b-type transitions have been measured for each rotamer. The a-type transitions belong to the qRK , qQ1, qQ2, qQ3 and qQ4 branches and the b-type absorption lines encompass the Ka = 1 - 0, 2 - 1, 3 - 2, 4 - 3 and 5 - 4 rotational sub-bands. The rotational constants and all quartic and sextic centrifugal distortion constants have been determined for each rotamer using Watson's reduced Hamiltonian. In addition to the measured line positions the frequencies of some selected low-J transitions, not observed in this work but of potential astrophysical interest, have been listed as an aid in the interstellar search for monothioformic acid.

Allostery and conformational free energy changes in human tryptophanyl-tRNA synthetase from essential dynamics and structure networks

2009 ◽  
Vol 78 (3) ◽  
pp. 506-517 ◽  
Author(s):  
Moitrayee Bhattacharyya ◽  
Amit Ghosh ◽  
Priti Hansia ◽  
Saraswathi Vishveshwara
Keyword(s):  
Free Energy ◽  
Trna Synthetase ◽  
Essential Dynamics ◽  
Conformational Free Energy

scholarly journals Effects of Solvent Polarity on Solvation Free Energy, Dipole Moment, Polarizability, Hyperpolarizability and Molecular Properties of Metronidazole

2016 ◽  
Vol 19 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Mohammad Firoz Khan ◽  
Ridwan Bin Rashid ◽  
Md Yeunus Mian ◽  
Mohammad S Rahman ◽  
Mohammad A Rashid
Keyword(s):  
Free Energy ◽  
Dipole Moment ◽  
Gas Phase ◽  
Chemical Potential ◽  
Solvent Polarity ◽  
Solvation Free Energy ◽  
Molecular Properties ◽  
Chemical Hardness ◽  
Electrophilicity Index ◽  
Polar Solvents

A computational study of medium effect on solvation free energy, dipole moment, polarizability, hyperpolarizability and different molecular properties like chemical hardness & softness, chemical potential, electronegativity and electrophilicity index of metronidazole have been reported in this paper. Becke, 3-parameter, Lee-Yang-Parr (B3LYP) level of theory with 6-31G (d,p) basis set was applied for gas phase and solution. The effect of solvent polarity on solvation free energy, dipole moment, polarizability, hyperpolarizability and molecular properties were calculated by employing Solvation Model on Density (SMD). The solvation free energies and dipole moment of metronidazole were found to be increased in nonpolar to polar solvents. The dipole moment of metronidazole was higher in different solvent than that of the gas phase. Moreover, from non-polar to polar solvents the chemical potential, electronegativity and electrophilicity index were increased. On the other hand, opposite relation was found in the case of chemical hardness and softness. The results obtained in this study may lead to understand the stability and reactivity of metronidazole and the results will be of assistance to use the title molecule as reaction intermediates and pharmaceuticals.Bangladesh Pharmaceutical Journal 19(1): 9-14, 2016

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