The Molecular Structure of trans-Cyclooctene.

Trætteberg, M.; Krogsgaard‐Larsen, Povl; Rømming, Chr.; Smidsrød, Olav; Dahl, O.; Buchardt, Ole; Schroll, G.

doi:10.3891/acta.chem.scand.29b-0029

Cited by 55 publications

(23 citation statements)

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“…4 The JP control parameters KNy, Kjp, Dma x and n are described in the text, Nf is the number of crystallographic observations and Np is the population of cluster number N c. Where appropriate the CSD reference codes cited represent those rings which are closest to the centroid of the cluster described by the mean torsion angles (°) with e.s.d. The C2-TCC form has been calculated as the minimum energy form (Traetteberg, 1975), some 13.1kJmo1-1 below the CC form. * Other refcodes refer to individual rings for which r l-r 8 are cited without e.s.d.…”

Section: Cyclooctene (8c2)mentioning

confidence: 99%

Symmetry-modified conformational mapping and classification of the medium rings from crystallographic data. IV. Cyclooctane and related eight-membered rings

Allen¹,

Howard²,

Pitchford³

1996

Acta Crystallogr Sect B

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Crystallographic observations of eight-membered ring conformations, retrieved from the Cambridge Structural Database, have been mapped and classified using symmetry-adapted deformation coordinates, principal component analysis and cluster analysis. Seven subsets of eight-membered rings, containing 11-32 conformational observations, have been analysed: cyclooctane (dataset 8C1), cyclooctene (8C2), cycloocta-l,3-diene (8C3), mono-exo-unsaturated carbocycles (8C4), monohetero (8A1), 1,5-dihetero (8A2) and 1,3,5,7-tetrahetero rings (8A3). The energetically preferred (by ~7 kJ mo1-1) boat-chair form is adopted by 26 of the 32 examples of 8C 1, although varying degrees of twist are induced by fusion to rings of sizes three, four and five. Crystallographic results for other subsets also populate the lower-energy areas of the appropriate potential energy hypersurface, but the analyses are complicated by the effects of ring fusion and by the small numbers of relevant crystal structures in some cases.

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Section: Cyclooctene (8c2)mentioning

confidence: 99%

Symmetry-modified conformational mapping and classification of the medium rings from crystallographic data. IV. Cyclooctane and related eight-membered rings

Allen¹,

Howard²,

Pitchford³

1996

Acta Crystallogr Sect B

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“…With larger rings, the difference in energy decreases, and for cycloundecene, the trans isomer is more The twisting distortion is well seen in the structure of trans-cyclooctene as determined by electron diffraction.' 391 The n-system is twisted out of planarity by 44".…”

Section: Twist Bendmentioning

confidence: 99%

The Concept of Strain in Organic Chemistry

Wiberg

1986

Angew. Chem. Int. Ed. Engl.

661

437

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"Die Ringschlieeung ist offenbar diejenige Erscheinung, welche am meisten iiber die raumliche Anordnung der Atome Auskunft geben kann. Wenn eine Kette von 5 und 6 Gliedern sich leicht, eine von weniger oder mehr Gliedern sich schwierig oder auch gar nicht schlieeen lafit, so miissen dafiir offenbar raumliche Griinde vorhanden sein. ... Die vier Valenzen des Kohlenstoffatoms wirken in den Richtungen, welche den Mittelpunkt der Kugel mit den Tetraederecken verbinden, und welche miteinander einen Winkel von 109'28' machen. Die Richtung der Anziehung kann eine Ablenkung erfahren, die jedoch eine mit der GroIje der Letzteren wachsende Spannung zur Folge hat."'**]This is the quintessence of the "ring-strain theory" formulated by Adolfvon Baeyer over one hundred years ago. Although it is today only one facet of the many aspects of strain theory, it has repeatedly stimulated experimental and theoretical chemists. Among the most spectacular of the recent successes in synthetic chemistry are the syntheses of tetra-tert-butyltetrahedrane and [ l.l.l]propellane. The reasons for the great stability of these two highly strained compounds are completely different. The experimental findings as well as the results of theoretical analysis by means of molecular mechanics and ab initio calculations have contributed decisively to our present state of knowledge of the structure, energy, and reactivity of organic compounds.

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“…To illustrate the quality of the chiroptical properties calculated by Program RPAC, we present in Table V I a summary of spectroscopic properties for ethylene distorted as in trans-cyclooctene [32], this time in a 5/3 1 G basis [33] augmented by diffuse functions as above, for a total of 38 basis functions. The S C F energy is -77.966801 3 hartrees.…”

Section: Sample Results: Ethylenementioning

confidence: 99%

“…The essential difference from the method of Davidson [24] is that the small eigenvalue problem in Eq. (32) is nonsymmetric, and we follow Liu [25] in optimizing several eigenvectors simultaneously. For large N , the present method is an order of magnitude faster than the Jprgensen-Linderberg method [20], and requires a much smaller work space in computer memory.…”

Section: M(m)a$") = [Wf7)]2a$m)mentioning

confidence: 99%

Large‐scale RPA calculations of chiroptical properties of organic molecules: Program RPAC

Bouman

Hansen

Voigt

et al. 1983

Int J of Quantum Chemistry

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The computational considerations involved in calculating ordinary and rotatory intensities and electronic excitation energies in the random phase approximation (RPA) are examined. We employ a localized orbital formulation in order to analyze the results in terns of local and charge-transfer excitations. Occupied orbitals are localized by the Foster-Boys procedure. The virtual space is transformed into a localized "valence" set that maximizes dipole strengths with the occupied counterparts, and a delocalized remainder. The two-electron integral transformation is performed with an efficient algorithm, based on Diercksen's, that generates only the particle-hole-type integrals required in the RPA. The lowest solutions of the RPA equations a;e obtained iteratively using a modification of the Davidson-Liu simultaneous vector expansion method. This allows the inclusion of the entire set of particle-hole states supported by a basis set of up to I02 orbitals. Calculations at this level give better excitation energies and intensities than SDCI methods, at substantial savings in computational effort. Comparative timings, computed results and analysis in terms of localized orbitals are given far planar and distorted ethylene using extended atomic orbital bases including diffuse functions. The results for planar ethylene are in excellent agreement with experiment.

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The Molecular Structure of trans-Cyclooctene.

Cited by 55 publications

References 0 publications

Symmetry-modified conformational mapping and classification of the medium rings from crystallographic data. IV. Cyclooctane and related eight-membered rings

Symmetry-modified conformational mapping and classification of the medium rings from crystallographic data. IV. Cyclooctane and related eight-membered rings

The Concept of Strain in Organic Chemistry

Large‐scale RPA calculations of chiroptical properties of organic molecules: Program RPAC

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