Confirmation of the H-bridged structure of the 2-butyl cation by comparison of experimental and ab initio IR frequencies

The IR spectrum of the 2-butyl cation, measured at –125 °C in an SbF5 matrix and calculated ab initio(MP2(FULL)/6-31G*), is characterized by a C(H [graphic omitted] ) C peak at 2175 cm–1 assigned to the nonclassical H-bridged (C2-symmetry) structure 1.