Structure and barrier of internal rotation of biphenyl derivatives in the gaseous state

Bastiansen, Otto; Samdal, Svein

doi:10.1016/0022-2860(85)85044-4

Cited by 217 publications

(99 citation statements)

References 36 publications

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“…If trifluoromethyl is the axial substituent, inevitably one of its halogen atoms collides with the axial hydrogen atoms at the 3-and 5-position of the ring. Our B values rank CF 3 Replacing the 2-phenyl substituent (in compound 1) by a pentafluorophenyl entity (in compound 9) should raise the barrier to the corresponding aryl-aryl rotation only moderately (the torsional activation energy of 2,2¢-difluorobiphenyl is approximately 4.8 kcal/mol 4 ) and increase that of the 2-R-phenyl/3¢Q*-phenyl rotation hardly at all. These assumptions were confirmed by the experiment ( Table 2).…”

Section: Discussionmentioning

confidence: 77%

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The biphenyl-monitored effective size of unsaturated functional or fluorinated ortho substituents

et al. 2010

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The size of a series of typical substituents has been probed by dynamic NMR measurements of the barriers to aryl-aryl rotation of the corresponding biphenyls. The resulting B values are meaningful because only mono-ortho substituted compounds were investigated and thus the results are not compromised by the non-additivity of multiple steric effects. On the basis of the chosen model system ethynyl and cyano groups were found to be slightly smaller than a phenyl ring. In contrast, vinyl and, in particular, formyl groups proved to be larger than phenyl. The latter difference is due to the loss of conjugation forces at the planar transition state. a-Hydroxyhexafluoroisopropyl is slightly more bulky than tert-butyl. Pentafluorophenyl and trifluoromethoxy exhibit nearly the same effective size as phenyl and methoxy, respectively. Trifluoromethyl is somewhat smaller than isopropyl.

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Section: Discussionmentioning

confidence: 77%

“…If the auxiliary 3¢-substituent harbors a pair of diastereotopic atoms or groups, e.g. 3 7.4 7 .1 6 .4 (9.7) C 2 H 5 8.7 -7 .7 (-) CH(CH 3 ) 2 11.1 1 1 .1 1 0 .1 (12.5) C(CH 3 ) 3 15.5 1 5 .6 1 4 .5 (-) NH 2 8.1 8 . 4 7 .1 (9.6) N(CH 3 ) 2 6.9 6 .8 5 .9 (7.8) N(CH 3 ) 3 18.…”

Section: Introductionmentioning

confidence: 99%

The biphenyl-monitored effective size of unsaturated functional or fluorinated ortho substituents

et al. 2010

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“…The energy barrier to rotation was found from experiments to be around 6.0 ( 0.5 kJ/mol for the planar and ortho configurations. [22][23][24] The MP2 calculations predict an energy barrier of 12.5 kJ/mol for the ortho and 7.7 kJ/mol for the planar configurations. Tsuzuki et al 18 performed similar MP2 calculations with larger basis sets as well as other methods like MP4 (fourth-order Møller-Plesset perturbation) and CCSD(T) (coupled cluster both single and double substitutions with perturbative estimation of the contributions of triple excitations).…”

Section: Torsional Potentialmentioning

confidence: 99%

Thermochemical Properties of Polycyclic Aromatic Hydrocarbons (PAH) from G3MP2B3 Calculations

Blanquart

Pitsch

2007

J. Phys. Chem. A

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In this article, we present a new database of thermodynamic properties for polycyclic aromatic hydrocarbons (PAH). These large aromatic species are formed in very rich premixed flames and in diffusion flames as part of the gas-phase chemistry. PAH are commonly assumed to be the intermediates leading to soot formation. Therefore, accurate prediction of their thermodynamic properties is required for modeling soot formation. The present database consists of 46 species ranging from benzene (C 6 H 6 ) to coronene (C 24 H 12 ) and includes all the species usually present in chemical mechanisms for soot formation. Geometric molecular structures are optimized at the B3LYP/6-31++G(d,p) level of theory. Heat capacity, entropy, and energy content are calculated from these optimized structures. Corrections for hindered rotor are applied on the basis of torsional potentials obtained from second-order Møller-Plesset perturbation (MP2) and Dunning's consistent basis sets (cc-pVDZ). Enthalpies of formation are calculated using the mixed G3MP2//B3 method. Finally, a group correction is applied to account for systematic errors in the G3MP2//B3 computations. The thermodynamic properties for all species are available in NASA polynomial form at the following address: http:// www.stanford.edu/group/pitsch/.

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“…The value observed in our case is close to the mean gas-phase value of 44.2 (1.2) ~ [22] in the unsubstituted biphenyl. The angle of twist of ortho-substituted biphenyls is certainly greater than this value, while meta-and para-substitutions seem to have little influence on it [23]. The ortho-substituted diphenyl moiety shows deviations in the bond angles, which contribute to the release of the intramolecular interactions between its atoms and the atoms of the rest of the molecule.…”

Section: Resultsmentioning

confidence: 97%

Solid-state structure and conformation of (Z)-2-(phenylbenzylidene)-3-quinuclidinone, an intermediate in the synthesis of quinuclidine derivatives

Santini¹,

Pedone

Benedetti

et al. 1994

Struct Chem

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(Z)-2-(2-phenylbenzylidene)-3-quinuclidinone, C2oHI9NO, Mr = 300.47D crystallizes in the monoclinic P21/c space group with a = 6.9809(2) /k, b = 19.0523(2) ik, c = 11.7733(1) ~k, = 100.92(2) ~ V = 1537.5(3) ~3, Z = 4, Dc = 1.298 g/cm 3, D~ = 1.29 g/cm 3 (flotation). Diffractometfic data, using CuKa radiation, X = 1.54178 A, were collected on plate-like crystals. The structure, solved by direct methods was refined to a final R value of 0.037 for the 2645 observed reflections with Fo > 3.0a(Fo). The molecule shows a trans conformation around the double bond. The quinuclidine and the diphenyl moieties present deformations in their geometric and conformational parameters due to the need of releasing intramolecular strains and/or nonbonded interactions.

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Structure and barrier of internal rotation of biphenyl derivatives in the gaseous state

Cited by 217 publications

References 36 publications

The biphenyl-monitored effective size of unsaturated functional or fluorinated ortho substituents

The biphenyl-monitored effective size of unsaturated functional or fluorinated ortho substituents

Thermochemical Properties of Polycyclic Aromatic Hydrocarbons (PAH) from G3MP2B3 Calculations

Solid-state structure and conformation of (Z)-2-(phenylbenzylidene)-3-quinuclidinone, an intermediate in the synthesis of quinuclidine derivatives

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