Quantitative studies on aromaticity and antiaromaticity

Abstract

The properties of the simplest aromatic compound, C3H3+, are fully consistent with expectations. Spectroscopic studies show that it is a symmetric cation with approximately the stability expected from simple quantum mechanical considerations. Various studies on cyclopropenyl anions reveal that they are undoubtedly resonance destabilized. Thus, the kinetic studies which have been done on rates of hydrogen exchange in this system can be shown to be consistent only with electronic destabilization in the antiaromatic cyclopropenyl anion. Direct thermodynamic determinations of the stability of cyclopropenyl anions can also be performed using a novel electrochemical procedure, and using this method very high pKas are found for some of these anions, indicating great stability. Resonance destabilization in cyclobutadiene can also be demonstrated by examining the basicity of a cyclobutadienocyclopentadiene anion and also by electrochemical studies on a fused naphthalenecyclobutadiene derivative. 1-Chioro-bicyclo [2, 2, 0] hexadiene has been prepared. On treatment with strong base it apparently eliminates HC1 to generate transient butalene (cyclobutadienocyclobutadiene), which is then trapped by the medium. © 1971, Walter de Gruyter. All rights reserved.