Transient chirality of anilides - The rotational spectrum of trans-benzanilide

Abstract The rotational spectrum of trans -benzanilide C 13 H 11 NO is reported for the most part of the cm -wave range (3–19 GHz). Heavy atom frame conversion between the two possible enantiomers surprisingly leads to significant tunnelling splittings in the observed spectrum. The large amplitude motion parameters for the occurring tunnelling as well as the nuclear quadrupole coupling constants for the 14 N were determined in addition to the rotational constants and quartic centrifugal distortion coefficients. Contrary to other trans -anilides, calculations indicate the existence of a non planar amide group in trans -benzanilide.