Conformational energy, and

Smith G D and R L Jaffe 1996. Quantum Chemistry Study of Conformational Energies and Rotational Energy Barriers in u-Alkanes. Journal of Physical Chemistry 100 18718-18724,... 

Another interesting question concerns the rate at which each tosylate undergoes elimination. A tosylate sample contains molecules with several different conformations. The size of each conformer population depends on conformer energy, and the more reactive tosylate will probably be the one with the largest population of reactive conformers, i.e., molecules whose geometries allow anti elimination. Which tosylate, cis or trans, will have a larger population of reactive conformers Explain how you reached this conclusion. 

The literature in this field is confusing because of a somewhat haphazard method of nomenclature that has arisen historically. This is compounded by some mistakes in structure determination, reported in early papers, and which are occasionally quoted. The first part of this chapter deals with nomenclature and with a brief overview of early work. Subsequent sections deal with the formation and metabolism of di-D-fructose dianhydrides by micro-organisms, and the formation of dihexulose dianhydrides by protonic and thermal activation. In relation to the latter topic, recent conclusions regarding the nature of sucrose caramels are covered. Other sections deal with the effects of di-D-fructose dianhydrides upon the industrial production of sucrose and fructose, and the possible ways in which these compounds might be exploited. An overview of the topic of conformational energies and implications for product distributions is also presented. 

Halgren TA, Nachbar RB. Merck molecular force field. IV. Conformational energies and geometries. / Comput Chem 1996 17 587-615. 

Table I. Conformational Energies and Average Benzo Ring Conformations of BPDEs Calculated with the MINDO/3 Approximation3...

As in the case of the MM2 force field, parameterization of MM3 for amines was based mainly on experimental data with occasional references to ab initio calculations, mainly to evaluate relative conformational energies and derive appropriate torsional parameters. As mentioned above, one notable difference between the two force fields is the removal of lp on sp3 nitrogens from MM3. This simplifies the treatment of vibrational spectra and allows for a realistic treatment of nitrogen inversion which could not be handled by MM2. As usual with MM3, parameterization was aimed at reproducing a variety of molecular properties such as structure, steric energy, dipole moments, moments of inertia, heat of formation and vibrational spectra. A complete list of MM3 parameters for amines is provided in Reference 6. 

The filament-bound complex relaxes through the release of stored conformational energy and returns to the resting state, myosin-ADP-Pj. 

Other forms for the pseudo-energy penalty term have also been investigated (61,62). In any case, pseudo-energy penalty term acts as a constraint on the overall energy of the system, which is a balance between favorable conformational energies and overall molecular alignment as measured by field-based similarity (dissimilarity). 

Halgren, T. A. (1999) MMFF VII. Characterization of MMFF94, MMFF94s, and other widely available force fields for conformational energies and intermolecular-interaction energies and geometries. J. Comput. Chem. 20, 730-748. 

Conformations conformational energies and changes The ligand may be able to exist in several conformations, one of which may have more suitable features this is true for G for instance, whose endo-endo form (see figure 8 below) contains a cavity that is nearer to a sphere than the cavities of the two other forms. Monocyclic ligands of type D may exist in folded conformations or may acquire such a conformation in the complexes (see below). The equilibrium conformation of a ligand depends... 

The selection of theoretical model with which to obtain the energy profile should be based on documented performance with regard to calculation of relative conformer energies and barrier heights. Full discussion has already been provided in Chapter 8. 

Fortunately, conformational analysis provides a variety of independent methods to determine conformations17. Nowadays, a prediction of conformational energies and their minimum is often facilitated by force-field18,19 and quantum-mechanical20 calculations, at least on a semiquantitative level. 

The conformational energies and helix parameters are calculated for the various states of polymethylphenylsilylene chain. The calculations are performed for the three different relative dispositions of the phenyls attached to three successive silicon atoms. The minima are invariably shifted from perfectly staggered positions. 

Ab initio calculations with full geometry optimization on diphenyl carbonate and diphenylpropane are carried out to determine the bond geometries and the conformational energies and then to compute the unperturbed chsin dimensions of the bisphenol A polycarbonate. Application of these results to the RIS model of the PC chain leads to the prediction of the unperturbed chain dimension. 

N 020 "Conformational Energies and Configurational Statistics of Copolypeptides containing L-Proline"... 

Conformational Energy and Unperturbed Chain Dimensions of Polypeptide Homopolymers ... 

N 110 "Spatial Configurations of Polynucteotide Chains. II. Conformational Energies and the Average Dimensions of Polyribonucleotides"... 

Figure 5-8 Conformational energies and rotational barriers in butane, the difference in energy between the anti and gauche forms is 0.8-0.9 kcal mole-1. The energies are relative to conformation 7 as zero.

Theoretical treatment of the conformational properties of the related l,4-benzodiazepin-2,5-dione ring system has received less attention but HF and DFT methods have been applied to examine the relative conformational energies and activation energy for the 4/-to-P-isomer interconversion <2004JST37>. The DFT method provided superior prediction of the bond distances and angles that were comparable to those observed by X-ray crystallography. 

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