THE SHAPE OF THE RING IN TRANS-1,3-DIBROMOCYCLOBUTANE

IR spectra of the title compound have been investigated as the vapour, in dilute solution, in various solid phases in a cryostat, and isolat ed in inert gas matrices. Raman spectra have been investigated using a Miller-Harney cell in the liquid and various solid phases. Evidence b ased on selective weakening of various peaks and, in the case of the p lanar ring, mutual exclusion will be presented for the following inter pretation of the shape of the ring: Vapour and liquid (puckered), crys tal I (somewhat flattened), crystal II (planar), and crystal III (puck ered). Support for the planar form from the ab initio calculations was provided by noting that, for five of the bands lying between 150 and 600 cm(-1), the calculated changes and directions of these changes on going from puckered to planar agreed well with those found experimenta lly. (C) 1997 Elsevier Science B.V.