The Molecular Structure of Cis and Trans Cyclohexanediol-(1,2). An Electron Diffraction Investigation by the Sector Method.

Ottar, B.; Hassel, O.; Sillén, Lars Gunnar; Linnasalmi, Annikki; Laukkanen, Pentti

doi:10.3891/acta.chem.scand.01-0521

Cited by 4 publications

(5 citation statements)

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“…However, on the basis of generalizations previously proposed for the dimethylcyclohexanes (37), Svirbely and Lander have suggested that the diequatorial conformation is the more probable. This conclusion is at variance with that of Ottar (222), based on electron diffraction studies.…”

Section: Cyclohexanediolscontrasting

confidence: 46%

“…Electron diffraction studies (222) of the vapors of the chair-form cis-and irans-cyclohexanediols give all the theoretical maxima corresponding to e-and p-oriented oxygen atoms, although at different intensities. This indicates that the oxygen atoms in both the cis-and the trans-l ,2-diol must be present in equatorial and polar positions.…”

Section: Cyclohexanediolsmentioning

confidence: 95%

“…The ee pp (or trans) form, on the other hand, also will consist of optically active molecules, but in this case the conversion process does not lead to isomerization and a separation of the optically active antipodes is theoretically possible. Indeed, optical resolution of Zrans-1,2-cyclohexanediol, which was shown (222) to exist predominantly as the diequatorial conformation, has been achieved (42). The crystals of the cfs-1,2diol contain both d-and Z-molecules, but since ring conversion converts the le, 2p conformation into its optical antipode, lp, 2e, it has not been possible to effect the resolution of the cis isomer.…”

Section: Monocyclic Carbon Compounds a Monosubstituted Cyclohexanesmentioning

confidence: 99%

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The Stereoisomerism of Cyclohexane Derivatives.

Orloff¹

1954

Chem. Rev.

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Section: Cyclohexanediolscontrasting

confidence: 46%

Section: Cyclohexanediolsmentioning

confidence: 95%

Section: Monocyclic Carbon Compounds a Monosubstituted Cyclohexanesmentioning

confidence: 99%

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The Stereoisomerism of Cyclohexane Derivatives.

Orloff¹

1954

Chem. Rev.

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“…it would be expected that for the cis compounds, -I t is seen in Table I1 that the values found for JAX+JBX are in excellent general agreement with this expectation. Evidence has been obtained that the cis compounds exist in solution in the chair forms (33). The slight difference between the shift for unbonded and bonded hydroxyl infrared frequency of 39 cm-l for the cis-diol and 32 cm-l for the trans isomer has been ascribed (34) to deformation of the cis compound from the perfect chair.…”

Section: Cis-compoundsmentioning

confidence: 86%

THE CONFORMATIONS IN SOLUTION OF trans-CYCLOHEXENE DIHALIDES AND cis- AND trans-1,2-CYCLOHEXANEDIOLS AND DERIVATIVES

Lemieux¹,

Lown²

1964

Can. J. Chem.

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trans-1,4,4-Trideuteriocyclohexene dichloride, dibromide, and diiodide and the 1,4,4-trideuterio-cis-and trans-1,2-cyclohexanediols together with their 0-acetyl, 0-tosyl, and O-isopropylidene derivatives were synthesized. Their nuclear magnetic resonance (NMR) spectral parameters were obtained with a spectrometer operating a t 100 h1c.p.s. and employing double irradiation to establish the chemical shifts and the signs of the coupling constants. The interpretation of the data according to expectations based on the Karplus relationship, for dihedral angles and coupling constants, support the conformational equilibria assigned t o the tuans-dichloride and trans-dlbromide of cyclohexene on the basis of dipole moment measurements (previously published results). The results indicate that trans-cyclohexene diiodide exists t o about 84yo in the diaxial conformation. I11 the case of the 1,2-cis-disubstituted cyclohexanes, the occurrence of the signal for the 3-hydrogen in trans relation t o the 2-hydrogen a t loxver field than its geminal 3-hydrogen is assigned to the deshielding influence on the 3-hydrogen when in axial orientation by a n opposing axial oxygen a t the 1-position. Support for this contention was obtained by determination of the chemical shifts of the geminal hydrogens a t the 3-and 5-positions of the cis-and trans-4-t-butyl-2,2,6,6-tetradeuterio-1-methylcyclohexanols. The conformational equilibria indicated for the l,2-diol, l,2-diacetox), and 1,2-ditosyloxy trans derivatives of 1,4,4-trideuteriocyclohexane by N h l R parameters obtained from the spectrum of the 0-isopropylidene derivatives of the tuans-diol allowed conclusions regarding the non-bonded interaction energies involved. The Karplus relation had to be adjusted to the form, J+ = 14.7 cosZ@ -0.2 (0'-4-90") and J+ = 11.2 cos24 -0.2 (90"-4-18O0), t o accommodate the results. Solvent effects on conformation are noted. Also, the investigation provided further evidence for the opposite signs of the coupling constants for geminal and vicinal hydrogens. A consideration of the chemical shifts observed for a variety of derivatives of cyclohexanol appears to indicate that intramolecular shielding effects are better accounted for on the basis of neighboring atomic groupings than on the basis of individual chemical bonds.Attempts have been made previously to study-the conformational equilibria of the trans-cyclohexene dihalides in benzene solution by the measurement of dipole moments (1) and by observation of the chemical shifts of protons adjacent to the halogen atoms (2). Both of these methods suffer from disadvantages; in the first, it is impossible t o estimate the molecular dipole in the diaxial conformation, i.e. of allowing for dipolar contributions from the cyclohexane skeleton (3). The second method requires the assumption that the usual orientational effects on chemical shifts apply (4,5). This latter assumption, as it transpired, proved to be justified in the case of the trans-dihalides but could not have been foreseen and would not hav...

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“…The apparent spontaneity and rapidity of the reaction is probably accounted for by the fact that the energy barrier to this attack is lowered, by the proximity of the anomeric oxygen (a-configuration) to the sulfate substituent in the adjacent equatorial position. With the glucose moiety in the very probable C-1 conformation, the anomeric oxygen is separated from the oxygen at the 2 position by about 2.85 A (14). In a Fisher-Hirschfelder-Taylor model construction, the anomeric oxygen and the sulfur are, in fact, in contact.…”

mentioning

confidence: 99%