More than 100 solvents and the gas phase were used to develop a solvent dipolarity‐polarizability scale that combines the medium dipolarity and polarizability into a single parameter (SPP) calculated from the UV‐visible spectra of 2‐(dimethyl‐amino)‐7‐nitrofluorene (DMANF) and its homomorph 2‐fluoro‐7‐nitrofuorene (FNF). The proposed scale compares favourably for nonprotic solvents with existing solvent polarity scales including Kosower's Z, Dimroth and Reichardt's ET(30), Brooker's χR, Dong and Winnick's Py; Kamlet, Abboud, and Taft's π*, and Drago's S′ scale. When data are derived from electronic transitions, they provide an accurate description for the solvent effect in UV‐Vis, IR, NMR, and fluorescence spectroscopy as well as in other chemical areas including thermodynamics and kinetics.

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4-(N,N-dimethylamino)phenylethyne has been satisfactorily prepared by the Wittig reaction between chloromethylene(tripheny1)phosphine ylide and 4-(N,N-dimethylamino)benzaldehyde, followed by hydrochloric acid elimination. 1,4-Bis [4-(N,N-dimethylamino)phenyl]-buta-l,3-diyne was obtained by oxidative dimerization in good yield. The dimer forms a 1 : 1 charge-transfer complex with TCNE, an X-ray structure analysis of which is reported.