The electronic spectrum of (?)-s-(ps)-2,5,3',6'-tetrahydro[2.2]paracyclophane-2-carboxylic acid

A new, efficient route was used in the synthesis of 2,2]paracyclophane-2-carboxylic acid. The chiral acid was then resolved and the Birch reduction performed yielding one enantiomer of tetrahydro2,2]paracyclophane-2-carboxylic acid. The UV spectrum of tetrahydro2,2]paracyclophane-2-carboxylic acid in isopentane shows one absorption at 206 nm (?_max=5271). There are three bands observed in the CD spectrum in isopentane at 236 nm (θ] = 1.8 × 10⁴), 201 nm (θ]=-16×10⁴) and a positive band indicated below 180 nm but not observed, in ethanol the CD spectrum exhibits a band at 205 nm (θ]= 1.5×10⁴) and the UV spectrum shows a band at 208 nm (?_max=5915). The bands were assigned and possible reasons for the occurrence of a π→π^* transition at unexpectedly long wavelengths are discussed.