Ring puckering splitting and structure of indan

The ground state ring puckering splitting of the cyclopentane ring of indan has been precisely determined (Delta E-01 = 22.364(1) MHz) by measuring the very weak mu(c)-type transitions with pulse jet Fourier transform microwave spectroscopy. In addition, the rotational spectra of all C-13 monosubstituted isotopologues have been assigned and measured in natural abundance, leading to an accurate structure of the heavy atoms frame. (C) 2015 Elsevier Inc. All rights reserved.