Electron Diffraction Investigation of Molecules Containing a Cyclohexane Type Six-membered Ring.

Davis, Michaël I.; Hassel, O.; Arro, Leonida; Kvande, P. C.; Meisingseth, E.

doi:10.3891/acta.chem.scand.17-1181

Cited by 255 publications

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“…The lengths of the two C-O bonds, mean 1.431 (3) A, may be compared with the C-O lengths in dioxane [1.423 (3) A, Davis & Hassel, 1963]. The two ring C-C lengths, mean 1.516 (3) A, tend to be slightly shorter than the bonds, determined by electron diffraction, in cyclohexane [1.528 (5) A, Davis & Hassel, 1963]. The C-CH 3 length is equal to the C-CH 3 lengths in 2,5-dimethylhexane-2,5-diol [mean 1.524 (2) A; Helmholdt, 1975].…”

Section: The Mem Groupmentioning

confidence: 99%

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C

Bosch¹,

Bodegom²

1977

Acta Crystallogr Sect B

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M. NASR EDDINE, E. F. BERTAUT, M. ROUBIN ET J. P~RIS 3013 V. ConclusionNous avons &udi6 par diffraction de rayons X, temperature et ~t concentration variable, les solutions solides Cr~_xVxN. Pour x < ], chacun des compos6s se d6forme au-dessous d'une certaine temp6rature To(x ) que nous avons pu d6terminer. La d6formation, brutale dans CrN pur, s'&ale sur plusieurs dizaines de K dans les solutions solides sans atteindre tout l'6chantil-Ion, m6me aux temp6ratures les plus basses. La fraction d6form~e de l'6chantillon p(x, T) appartient au groupe d'espace Pnmm. The intensities were collected at -160°C. Refinement decreased R to 0.075 for 4163 independent counter reflexions. The structure consists of TCNQ columns united to form sheets parallel to (010) with MEM ions placed in the holes between the sheets. Within a column interplanar spacings of 3.15 and 3.27/k alternate, and for successive spacings the overlap between the TCNQ moieties is different, thus giving rise to dimers in the stack. The overlap within the dimer is of the ring-external bond type. The dimerization requires a reconsideration of the electronic and magnetic properties measured earlier.

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Section: The Mem Groupmentioning

confidence: 99%

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C

Bosch¹,

Bodegom²

1977

Acta Crystallogr Sect B

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“…The C-S-C angles are close to 105 °. As in other structures of macrocyclic polyethers, the C-C bonds found for (I) are short compared to the C-C bond distance of 1.523 A for 1,4-dioxane (Davis & Hassel, 1963), while the C-O and C-S bond lengths appear to be normal (Dalley, 1978). The shortening of C-C bond lengths in cyclic polyethers has been discussed extensively (Mercer & Truter, 1973;Dunitz etal., 1974;Goldberg, 1975;Dalley, 1978).…”

Section: Metal-cation Complexes Of C12h2405smentioning

confidence: 99%

Correlation of molecular conformation and thermodynamic stability of metalcation complexes of 1,4,7,10,13-pentaoxa-16-thiacyclooctadecane

Campbell¹,

Dalley²,

Izatt³

et al. 1981

Acta Crystallogr Sect B

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The results of crystal-structure analyses of 1,4,7,10,13-pentaoxa-16-thiacyclooctadecane (I) and its complexes with NaSCN, KSCN, RbSCN and AgNO3 are discussed. In all four complexes the cation coordinates to the five O atoms of the polyether sulfide (I). The sulfur-cation interaction for the complexes depends on the cation. The sulfur-cation interaction is strong and partially covalent with the Ag ÷ complex, but weak with the K ÷ and Rb ÷ complexes. In these three structures the S atom is directed into the cavity of the ligand. There is no interaction between the S and the cation in the Na ÷ complex. In both the Na÷-complexed and uncomplexed ligand, the S atom is directed away from the cavity of the ligand. The cation-oxygen ion-dipole electrostatic interaction is the main factor in the thermodynamic stability of the alkali-metal complexes, while the Ag ÷ complex is stabilized by both the cation-oxygen and cation-sulfur interactions. Correlations are made between the thermodynamic stabilities of cation complexes of 1,4,7,10,13,16-hexaoxacyclooctadecane, 1,4,7,10,13-pentaoxacyclopentadecane, 1,4,7,10,13,16-hexaoxacyclooctadecane-2,6-dione and (I), and molecular conformation determined by X-ray diffraction. These correlations provide a basis for determining the effect various ligand parameters have on the thermodynamic stability of polyether complexes.

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“…This flattening of six-membered ring systems in comparison with the ideal chair form seems to be the rule rather than the exception. It has been found in dioxane (Davis & Hassel, 1963), several dihalogenodioxanes (Altona & Romers, 1963a, b;Altona, Knobler & Romers, 1963a, b), 2,3-dichlorodithiane (Kalff & Romers, 1965 and in 2fl,3a-dichloro-5ct-cholestane (Geise, Romers & Rutten, 1966). The equatorial halogen atoms do not give rise to an extra distortion of ring A in contrast with the axially substituted chlorine atoms in the 2fl,3~ compound.…”

Section: Molecular Geometry and Packingmentioning

confidence: 99%

The conformation of non-aromatic ring compounds. XVII. The crystal structures of 2α,3β-dichloro- and 2α,3β-dibromo-5α-cholestane

Geise¹,

Romers²

1966

Acta Cryst

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The isomorphous crystal structures of 2ct,3p-dichloro-5~-cholestane and the corresponding dibromo compound were determined from a projection along [010] with the aid of room temperature data. Both structures were refined, the former with three-dimensional room-temperature data, and the latter with three-dimensional data collected at -120°C. The unit-ceU dimensions of the bromo compound at -120°C are: a = 14.99, b = 7.75, c = 11.49/~, B= 105 ° 17', Z= 2.The space group is P21. The rings A, B and C have the chair form and ring D the conformation of a half chair with approximate symmetry (72. The cyclohexane rings, flatter than in the ideal model, give rise to a small enlargement of the angle between the carbon-halogen bonds. It proved possible to give crystallographic evidence for the structure of 2~-bromo-3p-chloro-5ct-cholestane, which is isomorphous with the compounds mentioned above.

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Electron Diffraction Investigation of Molecules Containing a Cyclohexane Type Six-membered Ring.

Cited by 255 publications

References 0 publications

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C

Correlation of molecular conformation and thermodynamic stability of metalcation complexes of 1,4,7,10,13-pentaoxa-16-thiacyclooctadecane

The conformation of non-aromatic ring compounds. XVII. The crystal structures of 2α,3β-dichloro- and 2α,3β-dibromo-5α-cholestane

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Electron Diffraction Investigation of Molecules Containing a Cyclohexane Type Six-membered Ring.

Cited by 255 publications

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The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)2, at –160°C

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)2, at –160°C

Correlation of molecular conformation and thermodynamic stability of metalcation complexes of 1,4,7,10,13-pentaoxa-16-thiacyclooctadecane

The conformation of non-aromatic ring compounds. XVII. The crystal structures of 2α,3β-dichloro- and 2α,3β-dibromo-5α-cholestane

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The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C

The crystal structure of the 1:2 complex of N-methyl-N-ethylmorpholinium and 7,7,8,8-tetracyanoquinodimethane, MEM(TCNQ)₂, at –160°C