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Oscillation of spontaneously generated optical activity in (\pm)-1-(p-nitrobenzoyloxy)indane solutions: 'serial $S_N2$ reactions' in aggregates supported by the crystal structure. Frozen $S_N2$ transition states and enantioselective distortions

Sosale, Chandrasekhar and Chopra, Deepak and Guru Row, Tayur N (2005) Oscillation of spontaneously generated optical activity in (\pm)-1-(p-nitrobenzoyloxy)indane solutions: 'serial $S_N2$ reactions' in aggregates supported by the crystal structure. Frozen $S_N2$ transition states and enantioselective distortions. In: Journal of Molecular Structure, 738 (1-3). pp. 113-116.

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Abstract

(\pm)-Indan-1-yl 4-nitrobenzoate upon dissolution in $CH_2Cl_2$, surprisingly displays optical activity-usually levorotation which swings to dextrorotation over several hours, and gradually vanishes. Its crystal structure (redetermined for this study) reveals an unusually close contact (1.471\AA) between the $C_1$ chiral centre in one molecule, and the oxygen atom at $C_1$ in a neighbouring molecule of the same 'R' configuration. Corresponding changes in bond lengths and torsion angles indicate a set of frozen $S_N2$ transition states. These interactions apparently persist in the aggregated solution, enabling a ’serial $S_N2$‘ process which can invert the $C_1$ configurations in the (presumed) chiral aggregates. The selective distortion of the 'R' enantiomer in the crystal, and the spontaneous generation of optical activity upon dissolution, indicate processes that are akin to a second order asymmetric transformation.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier.
Keywords: Crystal structure;Frozen transition state;(Nitrobenzyloxy)indane;Optical activity;Oscillation;SN2 reaction;X-ray diffraction
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Chemical Sciences > Organic Chemistry
Date Deposited: 11 Jun 2007
Last Modified: 19 Sep 2010 04:38
URI: http://eprints.iisc.ernet.in/id/eprint/11174

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