Resolution and Enantiomerization Barrier of Tetramesitylethylene

Erez Gur, Silvio E. Biali, Zvi Rappoport, Yuriko Kaida, Yoshio Okamoto

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The 1H NMR spectrum of tetramesitylethylene (2) was analyzed, and the signals were assigned by means of a 2D NOESY spectrum. Attempts to observe anisochrony of the enantiotopic groups of a racemic mixture of 2 in a chiral solvent by 1H NMR were unsuccessful. Molecular mechanics and MNDO calculations satisfactorily reproduce the ground-state conformation. The calculated barrier for the enantiomerization process is 21.8 (MM2) and 28.2 (MNDO) kcal mol−1. 2 was chromatographically resolved on a (+)-poly(triphenylmethyl)methacrylate (PTrMA) column. Its specific rotation is [α]25 = −12100° at 365 nm and −2300° at 589 nm (d line). The activation parameters for the enantiomerization of 2 in perhydrofluorene are ΔG = ΔH = 39.6 kcal mol‒1 and ΔS = 0 cal mol−1 K−1. The barrier for 2 is the highest determined experimentally for a correlated rotation.

Original languageAmerican English
Pages (from-to)3689-3693
Number of pages5
JournalJournal of Organic Chemistry
Issue number13
StatePublished - 1 Jun 1992


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