The anomeric and reverse anomeric effect. A simple energy decomposition model for acetals and protonated acetals

1992 ◽  
Vol 70 (5) ◽  
pp. 1562-1572 ◽  
Author(s):  
F. Grein ◽  
P. Deslongchamps
Keyword(s):  
Lone Pair ◽  
Electronic Energy ◽  
Anomeric Effect ◽  
Energy Term ◽  
Energy Decomposition ◽  
Additional Energy ◽  
Relative Stabilities ◽  
A Value ◽  
Stabilization Energies ◽  
A Charge

Geometry optimizations at the 6-31G** level were performed on various conformers of XHmCH2YHn and XHmCH2YHn+I+ (protonated), with X, Y = N, O. The resulting anomeric stabilization energies were decomposed into steric, electrostatic (lone pair – lone pair, lone pair – hydrogen), and electronic contributions. Using approximate values for steric and electrostatic terms, the electronic energy was determined to be about −2 kcal/mol for the anomeric effect to arise from O, and −2.5 kcal/mol if it arises from N. For protonated systems, an additional energy term for the reverse anomeric effect had to be added, having a value of −4 kcal/mol for O in OH-CH2-NH3+ and −5 kcal/mol for N in NH2C-H2-NH3+. The anomeric effect due to N drives NH2-CH2-OH2+ to a charge-dipole complex of the type NH2=CH2+… OH2. The energy parameters obtained have been applied to predict relative stabilities of various conformers of methanetriol, aminomethanediol, and protonated methanetriol, with good success.

Microsolvation of CH+ in helium: An ab initio study

2016 ◽  
Vol 15 (02) ◽  
pp. 1650018
Author(s):  
Mohammad Solimannejad ◽  
Behnia Sadat Mirhoseini ◽  
Mehdi D. Esrafili
Keyword(s):  
Ab Initio ◽  
Decomposition Analysis ◽  
Zero Point ◽  
Basis Set ◽  
Energy Decomposition Analysis ◽  
Energy Decomposition ◽  
Point Energy ◽  
Basis Set Superposition Error ◽  
Polarization Effects ◽  
Stabilization Energies

In the present study, microsolvation and interaction of the CH[Formula: see text] cation with He[Formula: see text] clusters are investigated by means of ab initio calculations at MP2/aug-cc-pVTZ and QCISD/aug-cc-pVTZ levels. Stabilization energies of the studied complexes including basis set superposition error (BSSE) and zero point energy (ZPE) corrections are in the range of [Formula: see text][Formula: see text]kJ/mol and [Formula: see text][Formula: see text]kJ/mol. A good linear correlation is found between the stabilization energy and stretching frequency shift ([Formula: see text]) in the studied complexes. According to energy decomposition analysis, it is found that polarization effects are the major source of the attraction in these complexes.

Zur Theorie der Kernrotationen

1961 ◽  
Vol 16 (11) ◽  
pp. 1119-1124
Author(s):  
Lothar Meichsner
Keyword(s):  
Additional Term ◽  
Heavy Nuclei ◽  
Energy Term ◽  
Max Planck ◽  
Rotating System ◽  
Additional Energy ◽  
Moments Of Inertia ◽  
Secondary Conditions ◽  
Rare Earth Nuclei ◽  
Relative Coordinates

Calculations of the moments of inertia of heavy nuclei without taking into account nucleonic interactions yielded values about twice the experimental ones. Such calculations were done at the Max-Planck-Institut für Physik for some rare-earth nuclei. A paper written by the author at the same institution offers a better agreement already if the nucleonic interactions again are neglected. It considers the fact that the nucleons do not move independently of one another in the rotating system of coordinates since introduction of Eulerian angles necessarily imposes secondary conditions on the relative coordinates of the nucleons. In consequence of this, an additional energy term, called „Zwangsenergie", occurs. After presenting the main results of the mentioned paper it is shown that this additional term alters energy differences entering the effective reciprocal moments of inertia in the sense of enlarging these moments, i. e., diminishing the effective moments of inertia, and that this contribution is not negligible. The presented theory differs from that of INGLIS by treating the rotations of the axially deformed potential quantum-mechanically instead by the help of a classical angular velocity.

Some reactions of 2,4-dimethoxytetrahydropyrans

1969 ◽  
Vol 47 (17) ◽  
pp. 3099-3106 ◽  
Author(s):  
M. J. Baldwin ◽  
R. K. Brown
Keyword(s):  
Room Temperature ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Temperature Reaction ◽  
Trans Isomers ◽  
Kcal Mole ◽  
A Value ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Acid-catalyzed elimination of methanol from 2,4-dimethoxytetrahydropyran (1) produces 2-methoxy-5,6-dihydro-2H-pyran (3) rather than the expected olefin 4-methoxy-3,4-dihydro-2H-pyran (2).The reaction of 1,3-dibromo-5,5-dimethylhydantoin with 3 in ether – methanol gives a 2:1 mixture of the isomers 3β-bromo-2α,4α-dimethoxytetrahydropyran (5a) and 3α-bromo-2α,4β-dimethoxytetrahydropyran (5b) respectively. A rationale is given to explain the preponderance of 5a over 5b and the highly selective attack of the bromine of the hydantoin and the methanol on C-3 and C-4 respectively of the double bond of 3. Reduction of 5ab with zinc in ethanol provides only compound 3.The room temperature reaction of 1 in a mixture of water and 1,2-dimethoxyethane containing Amberlite IR-120, produces 2-hydroxy-4-methoxytetrahydropyran (6) as an equilibrium mixture of cis and trans isomers in the ratio 1:1. This gave a value of 0.9 kcal/mole for the anomeric effect in 6. Pyrolysis of the derivative, 2-acetoxy-4-methoxytetrahydropyran failed to produce the olefin 2 and resulted only in extensive decomposition.

On the Charge-Dependent Matrix Element Between the 9.516 MeV 4+ T = 1 Level and the 8.439 MeV 4+ T = 0 Level of 24Mg

1986 ◽  
Vol 41 (8) ◽  
pp. 1031-1033 ◽  
Author(s):  
C. T. Yap ◽  
E. L. Saw
Keyword(s):  
Matrix Element ◽  
Circular Polarization ◽  
Coulomb Potential ◽  
Ground State ◽  
Asymmetry Parameter ◽  
Deformation Parameter ◽  
Recent Measurement ◽  
Polarization Asymmetry ◽  
A Value ◽  
A Charge

A recent measurement of the ß - y circular polarization asymmetry parameter A on the isospinforbidden ß + decay of the ground state of 24Al to the 8.438 MeV 4+ T= 0 state of 24Mg yields a charge-dependent matrix element ⟨ VCD⟩Mg between the 9.516 MeV 4+ T = 1 state and the 8.439 MeV 4+ T = 0 state of 24Mg of (106 ± 40) keV, which is the largest measured value obtained so far in ß decay. Our calculation using Nilsson’s wavefunctions and a spherical Coulomb potential results in a value of 87 keV for ⟨ VCD⟩Mg . Variation of the value of ⟨ VCD⟩Mg against the deformation parameter ß shows that theory agree very well with the measured ⟨ VCD⟩Mg for ß around 0.5.

On the nature of the anomeric effect in XHn—CH2—OH systems, with X = F, O, N, C

1992 ◽  
Vol 70 (2) ◽  
pp. 604-611 ◽  
Author(s):  
F. Grein ◽  
P. Deslongchamps
Keyword(s):  
Conformational Analysis ◽  
Lone Pair ◽  
Anomeric Effect ◽  
Bond Forming

Using geometry optimizations at the 6-31G** level, energies, bond distances, and charges were obtained for systems XHn—CH2—OH with X = F, O, N, C, for various rotational conformers of the OH group. Conformational analysis shows that systems with X = F and O receive anomeric stabilization due to a partial π-bond forming in the CH2—OH fragment of the molecule, amplified or diminished by lone pair repulsion (or dipole) energies. For the systems with N and C, no π-bond stabilization is found. However, the e-NH2—CH2—OH system is still stabilized due to favourable lone pair repulsion circumstances. Keywords: anomeric effect, abinitio studies, π-bonding model.

Interatomic Interactions for BCC Metals Based on the Low Order Moments of the Density of States

1992 ◽  
Vol 278 ◽  
Author(s):  
Stephen M. Foiles
Keyword(s):  
Large Deviations ◽  
Density Of States ◽  
Fourth Moment ◽  
Interatomic Potentials ◽  
Energy Term ◽  
Additional Energy ◽  
Electronic Density ◽  
Bcc Metals ◽  
New Feature ◽  
Low Order

AbstractA model of the energetics of bcc transition metals based on the low-order moments of the electronic density of states is presented. The new feature of the model is an additional energy term related to the fourth moment of the density of states. This term reflects the coarse shape of the density of states. The model is tested by the computation of point defect properties, phonon dispersions, structural energy differences and surface properties. The results are compared to experiment, ab-initio calculations and other model interatomic potentials. The results indicate that the inclusion of the fourth moment term in the energy does not significantly improve the description of properties of the bulk bcc metals. However, the fourth moment term substantially improves the description of large deviations from the bcc bulk such as surfaces and alternative crystal structures.

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