CYCLOBUTANECARBOXYLIC ACID, 3-CHLORO

The molecular structures of cyclobutane and several of its simply substituted derivatives have been investigated by i.r. and Raman spectroscopy. The energy barriers between the two puckered minima for cyclobutane and [ Hg]-cyclobutane have been determined (518 + 5cm" and 508 8cm , respectively). With chloro-, bromo-, and cyano-substituents, asymmetry is introduced into the potential function for ring inversion, and conformational isomers become possible. However, the best fit of the far-i.r. data was for asymmetric potentials with single minima. It was presumed that the minima correspond to puckered conformations with equatorial substituents. The Raman spectra of chloro-, fluoro-, and methyl-cyclobutane lead to similar conclusions. The vibrational spectrum of crystalline cyclobutanecarboxylic acid has been reported and is best interpreted in terms of a hydrogen-bonded dimeric structure with a centre of symmetry. 

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