A re-evaluation of conjugation and hyperconjugation: The effects of changes in hybridisation on carbon bonds

Dewar, Michael J. S.; Schmeising, H. N.

doi:10.1016/0040-4020(59)80102-2

Cited by 337 publications

(91 citation statements)

References 16 publications

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“…In particular the equalization in the C-C lengths of the chain is more pronounced. On the other hand the mean value of 1.543 ,~ for coupled C(sp2)-C(sp 2) bonds is greater even than the normal single-bond length for C(sp3) -C(sp 3) bonds (1.53 A), as reported for hydrocarbons (Dewar & Schmeising, 1959;Stoicheff, 1962). In these coupled trimethineoxonols the quinone character has completely disappeared.…”

Section: Interpretation Of Bond Lengths and Angles In Hydroxybenzoquimentioning

confidence: 52%

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Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect

Kulpe¹,

Dähne²

1978

Acta Crystallogr Sect B

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Section: Interpretation Of Bond Lengths and Angles In Hydroxybenzoquimentioning

confidence: 52%

“…Two bonds (1.32 ,4,) and four bonds (1.48 A) are close to the standard distances for C(spZ)-C(sp z) double and single bonds in hydrocarbons (Dewar & Schmeising, 1959;Stoicheff, 1962). It is generally accepted that there is only one non-polar limiting structure (3) with a pronounced energy minimum for p-benzoquinones.…”

Section: Introductionmentioning

confidence: 99%

Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect

Kulpe¹,

Dähne²

1978

Acta Crystallogr Sect B

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“…This is in excellent agreement with the mean value of 1.523 A for 18 C-C bonds in the furanose derivatives reported by Sundaralingam (1965). There is no evidence that the C(5)-C(6) bond, which has sp3-sp 2 orbital character by reason of the carbonyl group, is significantly shorter than an sp3-sp 3 bond, such as C(1)-C(2), for example, as suggested by Dewar & Schmeising (1959) in their discussion of the effects of orbital hybridization on bond lengths. The C-OH bonds are 1.409, 1.413, 1.416 A and again there • 1(1) 2…”

Section: Description Of the Structurementioning

confidence: 90%

The crystal structure of β-D-glucurono-γ-lactone

Kim¹,

Rosenstein²,

Corfield³

1967

Acta Cryst

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The crystal structure of fl-D-glucurono-~,-lactone, C6H806, has two molecules in a cell with a= 6.753, b = 7.488, c = 6"608/~, fl= 93" 18 °, space group P21. The structure was solved from the three-dimensional sharpened Patterson function using multiple minimum function and convolution methods on an IBM 1620 computer. Both photographic and automatic diffractometer data were measured. The former gave a terminal R index of 10 ~o and the latter 4 ~o. The molecule was found to have fused five-membered lactone and furanose rings, in agreement with an earlier deduction from chemical evidence. The rings, neither of which is planar, are inclined to each other so that the best planes containing four atoms in each make a dihedral angle of 111.3 °. The lactone group is not planar, having a carbon atom 0.26/~ O II out of the plane of the C-C-O group, which is planar. The C-O bond adjacent to the carbonyl group is 0"10/~ shorter than the other formal single C-O bonds in the molecule. The molecules are associated in the crystal by a very simple system of hydrogen bonding, which excludes one hydroxyl group and the ring oxygen atoms.

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“…As expected, the sum of the three angles around C (2) = 123"8 °, is 359.9 °. The length (1.381 +0.035 A) of the exocyclic carbon-carbon bond, C(2)-C(1) in this compound is in good agreement with 1.37 A in salicylic aldehyde (Wyekoff, 1969), but is shorter than the theoretically calculated (sp 2) single bond lengths between trigonally linked carbon atoms, 1.479 A (Dewar & Schmeising, 1959)and 1.477 A (Cruickshank & Sparks, 1960). The partial double-bond character (58 %) (Pauling, 1960, p. 236) of the exocyclic C(2)-C(1) bond may be attributed to the resonance of a number of structures in which the molecules can exist (Fig.…”

Section: Discussionmentioning

confidence: 72%

The crystal structure of p-dimethylaminobenzaldehyde hydrobromide

Dattagupta¹,

Saha²

1973

Acta Crystallogr Sect B

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p-Dimethylaminobenzaldehyde hydrobromide (CgHIINO.HBr) crystallizes in the monoclinic space group P2x/c with four molecules in the unit cell. The cell dimensions are a= 12-65+0-02, b= 10-20 _+ 0.02, c = 7"42 + 0"03 A, fl= 90 ° 30 + 20. The structure was solved by heavy-atom methods using threedimensional X-ray data. The positions of hydrogen atoms were located from a difference Fourier synthesis. The structure was refined by three-dimensional full-matrix least squares method leading to a final R value of 10.8 %. The intra-and intermolecular features of the structure are discussed in detail. The amino nitrogen atom has been found to assume a tetrahedral configuration. The planar benzene ring is almost coplanar with the aldehyde group. The partial double-bond character of the exocyclic C-C bond has been attributed to a number of resonance forms. The only hydrogen bond (between the amino nitrogen and the bromine atom) is of the type N+-H .. .Br-with a length of 3.127+0-018 A. The molecules are held together by van der Waals forces.

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A re-evaluation of conjugation and hyperconjugation: The effects of changes in hybridisation on carbon bonds

Cited by 337 publications

References 16 publications

Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect

Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect

The crystal structure of β-D-glucurono-γ-lactone

The crystal structure of p-dimethylaminobenzaldehyde hydrobromide

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A re-evaluation of conjugation and hyperconjugation: The effects of changes in hybridisation on carbon bonds

Cited by 337 publications

References 16 publications

Long bond distances betweensp2-hybridized carbon atoms. The polymethine coupling effect

Long bond distances betweensp2-hybridized carbon atoms. The polymethine coupling effect

The crystal structure of β-D-glucurono-γ-lactone

The crystal structure of p-dimethylaminobenzaldehyde hydrobromide

Contact Info

Product

Resources

About

Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect

Long bond distances betweensp²-hybridized carbon atoms. The polymethine coupling effect