Conformational effects in compounds with 6-membered rings—XI

Baldry, K.W.; Gordon, Marshall; Hafter, Russell; Robinson, Michael J.

doi:10.1016/0040-4020(76)88032-5

Cited by 21 publications

(15 citation statements)

References 20 publications

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“…33,54 Although neither method agrees quantitatively with the previous studies, 33,54 all three methods predict that the axial conformer should be favored. It should be noted that previous studies, 33,54 like ours, were made by comparison to benchmark values (in the earlier case, from 2,6-dimethylcyclohexanone derivatives), so all of these studies depend upon assumptions to determine equilibrium populations.…”

Section: Resultsmentioning

confidence: 61%

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Spectroscopic and X-ray Crystallographic Evidence for Electrostatic Effects in 4-Substituted Cyclohexanone-Derived Hydrazones, Imines, and Corresponding Salts

Dibble

Woerpel

2011

J. Org. Chem.

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The axial conformer of several 4-substituted cyclohexanone hydrazone salts was found to predominate in solution. Changes in the charge of the molecule and the polarity of the solvent led to changes in the conformational preference of each molecule that was consistent with electrostatic stabilization of the axial conformer. 1 H NMR spectroscopic analysis was utilized to determine the structure of cyclohexanone-derived substrates by comparison to conformationally restricted transdecalone derivatives and computational models. X-ray crystallography demonstrated that the axial configuration of a pendant benzyloxy group is the preferred conformation of an iminium ion in the solid state. The structure of a neutral hydrazone was also determined to favor the axial configuration for a pendant benzyloxy group in the solid state.

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Section: Resultsmentioning

confidence: 61%

“…To verify that these assumptions would yield meaningful results, we reexamined the reported 33,54 conformational preferences of 4-alkoxycyclohexanones 19 and 21 using two methods (Figure 3). Carbonate ketone 24 is included in the comparison as well.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and X-ray Crystallographic Evidence for Electrostatic Effects in 4-Substituted Cyclohexanone-Derived Hydrazones, Imines, and Corresponding Salts

Dibble

Woerpel

2011

J. Org. Chem.

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“…This is also the pattern found by NMR experiments at 308 K, though the observed shift in going from cyclohexane to water, 0.54 kcal/mol, is not as large. 36 The computed dipole moments of 3.15 D for the equatorial form and 3.27 D for the axial conformer in the gas phase would lead to the opposite trend, so this is an interesting case of the dominance of higher moments that is captured in the GB/SA treatment. Free Energies of Hydration for Ions.…”

Section: Resultsmentioning

confidence: 97%

Free Energies of Hydration from a Generalized Born Model and an All-Atom Force Field

2004

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The generalized Born/surface area (GB/SA) model of Still and co-workers was originally developed using partial atomic charges for organic molecules and ions from the OPLS united-atom force field. An efficient implementation of the GB/SA approach with the OPLS-AA (all-atom) force field is described here. Migration to the OPLS-AA model allows much broader application, and it also yields improved accuracy in predicting free energies of hydration. For 75 diverse, neutral organic molecules, the mean unsigned error is 0.6 kcal/mol with the OPLS-AA GB/SA model. Furthermore, effects of hydration on conformational equilibria are shown to be well represented, and results for free energies of hydration of a wide variety of ions are also in close accord with experimental data. As an even more general alternative, the use of partial charges from the CM1A procedure of Cramer, Truhlar, and co-workers has been tested on more than 400 organic molecules and ions. OPLS-AA force field parameters are also reported for primary alkyl halides, halobenzenes, and numerous ions.

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“…68 This stereochemical outcome can be analyzed by considering that the cation prefers the conformation 32, where the alkoxy groups at C-2, C-3, and C-4 are all in their favored orientations. 43,54,56 (12) Analyzing the reactions involving highly oxygenated fivemembered ring oxocarbenium ions added another level of complexity. For example, analyzing the C-glycosylation reactions of ribose derivatives (eqn 13) 69 required not only understanding the conformational preferences of the intermediate carbocations but also the preferred direction of nucleophilic attack.…”

Section: Investigations and Applications Of Electrostatically Stabili...mentioning

confidence: 99%

Electrostatic interactions in cations and their importance in biology and chemistry

2006

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Electrostatic effects exert strongly stabilizing influences on cations, in many cases controlling the conformational preferences of these cations. The lowest energy conformers are ones where the positive charge is brought closest to substituents bearing partial negative charges. These conformational biases, along with stereoelectronic effects, can control the stereoselectivity of reactions involving carbocationic intermediates.

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Conformational effects in compounds with 6-membered rings—XI

Cited by 21 publications

References 20 publications

Spectroscopic and X-ray Crystallographic Evidence for Electrostatic Effects in 4-Substituted Cyclohexanone-Derived Hydrazones, Imines, and Corresponding Salts

Spectroscopic and X-ray Crystallographic Evidence for Electrostatic Effects in 4-Substituted Cyclohexanone-Derived Hydrazones, Imines, and Corresponding Salts

Free Energies of Hydration from a Generalized Born Model and an All-Atom Force Field

Electrostatic interactions in cations and their importance in biology and chemistry

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