The central region of meso-3,4-diphenylhexane-2,5-dione

Balasubrahmanyam, S. N. ; Kulkarni, G. U. ; Gopalan, R. S. ; Kumar, A. S. ; Hiremath, U. S. (2003) The central region of meso-3,4-diphenylhexane-2,5-dione Journal of Molecular Structure, 645 (2-3). pp. 159-169. ISSN 0022-2860

Full text not available from this repository.

Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/S0022-2860(02)00537-9

Abstract

As with 1,2-diphenylethane (dpe), X-ray crystallographic methods measure the central bond in meso-3,4-diphenylhexane-2,5-done (dphd) as significantly shorter than normal for an sp3–sp3 bond. The same methods measure the benzylic (ethane C–Ph) bonds in dphd as unusually long for sp3–sp2 liaisons. Torsional motions of the phenyl rings about the C–Ph bonds have been proposed as the artifacts behind the result of a ‘short’ central bond in dpe. While a similar explanation can, presumably, hold for the even ‘shorter’ central bond in dphd, it cannot account for the ‘long’ C–Ph bonds. The phenyl groups, departing much from regular hexagonal shape, adopt highly skewed conformations with respect to the plane constituted by the four central atoms. It is thought that the thermal motions of the phenyl rings, conditioned by the potential wells in which they are ensconced in the unit cell, are largely libratory around their normal axes. In what appears to be a straightforward explanation under the ‘rigid-body’ concept, it appears that these libratory motions of the phenyl rings, that account, at the same time, for the ‘short’ central bond, are the artifacts behind the ‘long’ measurement of the C–Ph bonds. These motions could be superimposed on torsional motions analogous to those proposed in the case of dpe. An inspection of the ORTEP diagram from the 298 K data on dphd clearly suggests these possibilities. Supportive evidence for these qualitative explanations from an analysis of the differences between the mean square displacements of C(1) and C(7)/C(1a) and C(7a) based on the ‘rigid-body model’ is discussed.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Diphenylethanes; X-Ray Crystallography; Short and Long Measured Bond Distances; Calculated Bond Distances; Rigid-bond/Rigid-body Model; TLS Analysis
ID Code:103200
Deposited On:17 Feb 2017 11:59
Last Modified:17 Feb 2017 11:59

Repository Staff Only: item control page