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A Theoretical Study of the Factors that Contribute to the Conformational Energy of Six‐Membered Rings
Author(s) -
Abdulsalam Maryam,
Balilli Rabih,
Baello Rofe,
Booth Robert,
Suresh Sandeep,
Kasner Marc
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.559.44
Subject(s) - steric effects , chemistry , hyperconjugation , conformational isomerism , cyclohexane , anomeric effect , solvent effects , substituent , computational chemistry , electronic effect , solvent , ring (chemistry) , stereochemistry , anomer , molecule , organic chemistry
Various studies have shown that 2‐hydroxyltetrahydro‐ 2H ‐pyran has a negative conformational energy and is said to manifest an anomeric effect. The cause of the anomeric effect is not well understood and by computationally studying the energies and geometries of a series of compounds in a series of solvent systems, the contributions of steric factors, of hyperconjugation effects, of stereoelectronic interactions and solvent interactions to the relative stability of axial and equatorial conformers were investigated. A series of monosubstituted cyclohexanes with minimal electronic interactions were studied followed by a series of monosubstituted tetrahydro‐ 2H ‐pyrans. The relaxed scans of energy as a function of the orientation of the ring substituent of the tetrahydro‐ 2H ‐pyran series show the combination of the electronic effects and the steric effects and comparison to the scans of the cyclohexane series to the allowed separation of the electronic effects from the steric effects. Natural Bond Orbital analysis of the full sequence of both sets of compounds is used to establish the extent of any hyperconjugative effects. To study the solute‐solvent interactions, the energy and geometry studies were repeated using a continuum solvent model with water (ε = ~80), acetone (ε = ~20) and cyclohexane (ε = ~2) selected as the solvent.