Barriers to internal rotation in 1,3,5-trineopentylbenzenes

Author: Nilsson Bertil  

Publisher: Taylor & Francis Ltd

ISSN: 1362-3028

Source: Molecular Physics, Vol.27, Iss.3, 1974-03, pp. : 625-632

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Abstract

The usefulness of the double resonance technique in studying chemical exchange rates among molecular species, the N.M.R. spectrum of which appears as three exchanging AB spectra, has been demonstrated. To date this is the first application to rate processes involving coupled AB spin systems. A theoretical discussion of the validity of the method is given in terms of density matrix equations. Lifetimes (τ and T 1 eff ) were obtained from the time-dependent intensity decrease of a single line in an AB subspectrum by saturating one line in another AB subspectrum. The double resonance technique was also used as a check on the previously reported assignment of exchanging signals in the methylene proton spectrum of 1,3-dibromo-2,4,6-trineopentyl-5-nitrobenzene. Activation parameters obtained from the double resonance investigation are compared with data from the lineshape study.

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