The complete stereoselectivity in a cyclopropylmethyl-cyclopropylmethyl rearrangement which has been investigated is rationalized in terms of a highly preferred conformation of the transient a-acyl-or-cyclopropyl-carbenium ion. ... The cc-acyl-or-cyclopropyl-carbenium ion (A) is destabilized ... In order to investigate the role of these two opposing factors, the silver-assisted solvolysis of compound (1) a potential pre- cursor of a carbocation of type (A), has been studied. ...