Keto-enol tautomerism. Relative stabilization of enol isomers

1978 ◽  
Vol 31 (6) ◽  
pp. 1167 ◽  
Author(s):  
WJ Bouma ◽  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Vinyl Alcohol ◽  
Energy Difference ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Conformational Preferences ◽  
Relative Stabilization ◽  
Alcohol System ◽  
Li Substitution

Ab initio molecular orbital theory is used to examine the effect of simple π-electron-accepting substituents (Li, BeH, BH2) on the keto-enol equilibrium in the acetaldehyde-vinyl alcohol system. The enol-keto energy difference is increased slightly by α-Li substitution and decreased to a near-zero value by a BH2 substituent. The results are rationalized in terms of geminal interactions. The conformational preferences of substituted acetaldehyde systems (XCH2CHO; X = Li, BeH, BH2, CH3, F) are discussed. Three classes of rotational potential functions are distinguished on the basis of the σ-electron-donating or -accepting nature of the substituent.

Creation of a Simple Stable Enol. The Stabilizing Properties of the Diazonium Substituent

1979 ◽  
Vol 32 (7) ◽  
pp. 1401 ◽  
Author(s):  
MJ Ballard ◽  
WJ Bouma ◽  
L Radom ◽  
MA Vincent
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Electron Acceptor ◽  
Vinyl Alcohol ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Conformational Preferences ◽  
Alcohol System ◽  
Optimized Geometries

Ab initio molecular orbital theory is used to examine the effect of the diazonium substituent (N2+) on the keto-enol equilibrium in the acetaldehyde/vinyl alcohol system. The conformational preferences of the two isomers are examined, and optimized geometries obtained for the best conformers. The diazonium substituent is a strong π-electron acceptor and σ-electron acceptor, and accordingly destabilizes the keto isomer and stabilizes the enol isomer. The effect of the diazonium substituent is sufficiently large to make the enol isomer substantially lower in energy than the keto isomer.

An ab initio approach to creating a simple stable enol

1978 ◽  
Vol 31 (8) ◽  
pp. 1649 ◽  
Author(s):  
WJ Bouma ◽  
L Radom
Keyword(s):  
Potential Energy ◽  
Ab Initio ◽  
Energy Difference ◽  
Electron Acceptors ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Keto Form ◽  
Conformational Preferences ◽  
Alcohol System ◽  
Ab Initio Approach

Ab initio molecular orbital theory is used to examine the effect of four substituents (CN, NO2, NO and CHO) which are π-electron acceptors and σ-electron acceptors on the keto-enol equilibrium in the acetaldehyde/vinyl alcohol system. Each substituent destabilizes the keto isomer and stabilizes the enol isomer as desired and hence decreases the enol-keto energy difference. For the NO and CHO substituents, the effect is sufficiently large that the enol isomer is predicted to be slightly lower in energy than the keto form. The conformational preferences of the keto isomers are discussed in detail and a conformational potential energy map is presented for malondialdehyde.

Conformational preferences of the benzenedicarbaldehydes: an ab initio molecular-orbital, dipole-moment and Kerr-effect study

1984 ◽  
Vol 37 (3) ◽  
pp. 465 ◽  
Author(s):  
D Mirarchi ◽  
L Phillips ◽  
H Lumbroso ◽  
GLD Ritchie
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Kerr Effect ◽  
Dipole Moments ◽  
Effect Study ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Molecular Plane ◽  
Conformational Preferences ◽  
Kerr Constants

Ab initio molecular orbital theory at the STO-3G level is used to elucidate the structures and relative abundances of stable conformations of the three benzenedicarbaldehydes. In addition, new measurements of the infinite-dilution dipole moments and molar Kerr constants of these molecules as solutes in dioxan at 25�C are reported and analysed. The previously recognized inability of the simple group- additivity model to reliably predict the anisotropy in the polarizability of benzene-1,4-dicarbaldehyde is shown to be due to a redistribution of the polarizability in the molecular plane.

Ab initio molecular orbital theory

1986 ◽  
Vol 119 (2) ◽  
pp. 234 ◽  
Author(s):  
Luigi Olcari
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory

The Heat of Formation of Formaldimine

1992 ◽  
Vol 45 (1) ◽  
pp. 285 ◽  
Author(s):  
BJ Smith ◽  
JA Pople ◽  
LA Curtiss ◽  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Heat Of Formation ◽  
Molecular Orbital Theory ◽  
Orbital Theory

Ab initio molecular orbital theory at the G 2 level has been used to predict new values for the heat of formation of formaldimine (CH2=NH): ?Hfº0 = 94 ±10 kJ mol-1 and ?Hfº298 = 86 ±10 kJ mol-1.

Enthalpies of Formation of Gas-Phase N3, N3-, N5+, and N5-from Ab Initio Molecular Orbital Theory, Stability Predictions for N5+N3-and N5+N5-, and Experimental Evidence for the Instability of N5+N3-

2004 ◽  
Vol 126 (3) ◽  
pp. 834-843 ◽  
Author(s):  
David A. Dixon ◽  
David Feller ◽  
Karl O. Christe ◽  
William W. Wilson ◽  
Ashwani Vij ◽  
...  
Keyword(s):  
Ab Initio ◽  
Experimental Evidence ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Enthalpies Of Formation ◽  
Molecular Orbital Theory ◽  
Orbital Theory

Ab initio molecular orbital theory: a tool for THz spectroscopic investigation

2005 ◽  
Author(s):  
Inke Jones ◽  
Tamath J. Rainsford ◽  
Samuel P. Mickan ◽  
Derek Abbott
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Spectroscopic Investigation ◽  
Molecular Orbital Theory ◽  
Orbital Theory

ChemInform Abstract: THE RELATIONSHIP BETWEEN SUBSTITUENT EFFECTS ON ENERGY AND ON CHARGE FROM AB INITIO MOLECULAR ORBITAL THEORY

1977 ◽  
Vol 8 (47) ◽  
pp. no-no
Author(s):  
W. F. REYNOLDS ◽  
P. G. MEZEY ◽  
W. J. HEHERE ◽  
R. D. TOPSOM ◽  
R. W. TAFT
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Substituent Effects ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
The Relationship
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