Rotamer energy

The interconnection of configuration and conformation and their joint influence on NMR spectral parameters is of particular importance for acyclic aliphatic diastereomers, since these molecules are conformationally flexible and can adopt a large number of rotamers. Energy barriers for conformational interconversions are often small and can be overcome easily and frequently at... 

Table 4 Influence of Phase and Solvent Polarity upon Furfural Rotamer Energy Differences and...

TABLE 20. Rotamer energy differences for 1,2-dichloroethane in selected solvents... 

Sometimes rather than equilibrium constants, the differences in rotamer energies - for example, gosh- and trans-isomers - were calculated from the experiment. It is evident that these values are linearly proportional to the equilibrium constant logarithm. 

The differences in rotamer energies of l-fluoro-2-chloroetane in mixed solvents such as alkane-chloroalkane can be described by equation ... 

The observed rotamer energies Eg—are ca. 0.5 kcal mole in the dication and ca. 0 kcal mole for the monocation. The calculated energies are thus in general... 

VViberg K B and M A Murcko 1988. Rotational Barriers. 2. Energies of Alkane Rotamers. An Examination of Gauche Interactions. Journal of the American Chemical Society 110 8029-8038. 

Side chain generation is often a source of error. It will be most reliable if certain rules of thumb are obeyed. Start with structurally conserved side chains and hold them fixed. Then look at the energy and entropy of rotamers for the remaining side chains. Conventional conformation search techniques are often used to place each side chain. 

The small optical rotations of the alditols arise from the low energy barrier for rotation about C—C bonds, permitting easy iaterconversion and the existence of mixtures of rotational isomers (rotamers) ia solution (12). 

C Wilson, LM Gregoret, DA Agard. Modeling side-chain conformation for homologous proteins using an energy-based rotamer search. J Mol Biol 229 996-1006, 1993. 

A. Potential energy of substituted acetaldehydes as a iunction of the OCCR angle, relative to 4k energy of the syn (ZOCCR = 0°) rotamer isolated molecules. [Reproduced with permission of Ejsevier Science Publishing.]... 

The structures, energies, torsional barriers and vibrational spectra of three rotamers of tetrasulfane, H2S4, have been examined by Drozdova, Miaskiewicz and Steudel at the MP2/6-311G level [34]. Surprisingly, the cis-trans conformation (motif -l-H— symmetry Ci) is found to be most stable, followed by the all-cfs form (h—t symmetry C2), while the helical all-... 

---