The Microwave Spectrum of the Bimolecule Trifluoroacetic Acid · · · Cyclopropanecarboxylic Acid

We have investigated the microwave spectrum of the bimolecule trifluoroacetic acid • • • cyclo-propanecarboxylic acid in the region 1 to 4 GHz, where the low J transitions of this heavy complex appear. The measured μ -R branch transition frequencies were fitted to determine the rotational constants and three centrifugal distortion constants. With the assumption that the structures of the subunits remain unchanged upon complexation, the O • • • O distances of the hydrogen bridge bonds are determined as 2.62 A.