Abstract
By DTA calorimetry the enthalpy of valence isomerization of 1-t-butyl-dibenzo-2,5-bicyclo-(2,2,0)-hexadiene (9-t-butyl-9,10-Dewar-anthracene) 2 to 9-t-butylanthracene 1 has been determined as -172±5 kJ mol-1 in decaline at 350 K. Photochemically the isomerization 2→1 occurs with the high quantum yield of ΦR≅O.4 in contrast to the low quantum yield of the reverse photo-isomerization 1→2 of ΦR = 0.016 [5]. Since other meso-substituted anthracenes, e.g. 9-methyl-anthracene or 9-trimethylsilyl-anthracene do not photoreact to Dewar-isomers, it is concluded that a deformation of the anthracene sceleton is a prerequisite for this type of valence isomerization.
© 1946 – 2014: Verlag der Zeitschrift für Naturforschung
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.