Another Generic Reaction for Indanes

A plausible alternative (supplementary ) approach to the aromaticity of our diverse derivatives of indane and indene makes use of the deviation from thermoneutrality for the generic reaction  

We no longer have need of the enthalpy of formation of CH3-X-Y-Z-CH3. Again starting with the carbocyclic indane (X = Y = Z = CH2) (XfV)  

This reaction is exothermic by 22 kJ mol-1, a deviation that may be once again ascribed to release of the strain energy in the five-membered ring. (X = CO, Y = Z = CH2)  

This reaction is exothermic by 7 kJ mol-1. If we argue that this is due to the strain energy of the five-membered ring, we conclude that indane and 1-indanone have different strain energies, a plausible result. For 2-indanone (X = Z = CH2, Y = CO)  

This reaction is exothermic by 14 kJ mol-1, very nearly the same as for the isomeric 1-indanone. For indane-l,3-dione (X = Z = CO, Y = CH2) (XVII) we have  

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