Chair conformation and barrier to ring puckering in 1,3-benzodioxole

Non-planarity and barrier to ring puckering in phthalan

“…The variations of rotational constants upon vibrational excitation, which were not available to Hassan and Hollas [6], allowed us to discriminate between ring puckering and ring twisting, but on the basis of the chemistry it would be difficult to accept ring-twisting, which is to a first approximation a torsion around a double bond, as a 'soft' motion. The shifts of the Mgg in going from the ground to the vt = 1 state are very similar to those observed in indan [1], indoline [3], 1,3-benzodioxole [18], and catecholborane [19].…”

Structural Determinations and Dynamics on Floppy Molecular Systems

“…In a previous work we have recorded several vibronic bands of the S 1 ←S 0 electronic transition to determine the potential function governing the ring-puckering vibrational mode of this molecule [21]. The spectra of the different bands were accurately calibrated to the rotational constants of the ground state obtained by Caminati et al [22]. Thanks to the high resolution of our molecular beam spectrometer we have evidenced some errors in the assignment of the vibronic spectrum [14].…”

Large Amplitude Motions in 2,3-Cyclopentenopyridine

“…This was the case for indoline (5) and 1,3-ter than 0.1 MHz. The cell temperature was kept constant benzodioxole (7). In this last case the 2D model led to the at approximately 015ЊC.…”