Raman spectra and conformations of 2,2-dialkyl-1,3-dithio-5,6-benzocycloheptenes: coexistence of chair, boat and twist-boat forms

Raman spectroscopy has been applied to the title compounds; dithiaketals of acetone, methyl-ethylketone, ethylketone, pinacolone, cyclohexanone and fluorenone. A three-component chair⇋boat⇋twist-boat boat conformational equilibrium has been established for all compounds studied except the pinacolone derivative, which exhibits a two-component chair⇋boat equilibrium. Questions concerning the symmetry of the conformations based on depolarization data are discussed. © 1992