Morphing the Torsional Potential Energy Function from Local to Global Symmetry through a π Link: The Rotational Spectrum of ALFA, ALFA, ALFA-Trifluoro-p-tolualdehyde

We report the Fourier transform microwave spectrum of ALFA,ALFA,ALFA-trifluoro-p-tolualdehyde, utilizing internal dynamics to point out spatial orbital effects transferred through a conjugated bond system. The substitution in benzotrifluoride (ALFA,ALFA,ALFA-trifluorotoluene) of the hydrogen atom in position 4 with the aldehyde group breaks the global symmetry of the molecule spatially far away from the 6 locally equivalent minima of the σ-bound CF3 group and dramatically morphs the V6 potential energy function towards a one-order-of-magnitude dominating V3 barrier to the internal rotation of the CF3 top due to the electronic link of the PI-system transmitting the presences of the asymmetry. The value of the determined V3 barrier is 28.862 cm-1.