Thanks a lot for the insights! From the little I remember, a classic double bond reacts quite differently from a benzene ring. It appears that the A-(C=C)n-A' notation is a strongly simplified version of Kendall and Pelzs original research work, and just looking at A-(C=C)n-A' does not tell me imbecile, why hydroquinone and catchechol are devs, resorcinole is not, but pyrogallol is.

Just curious: based on Kendall-Pelz rule, would 1,3-Butadiene-1,4-diamine also work as a developer? I know, a substance which has a flash point below 65C falls squarely into the "things I won't work with" category, I ask this from a purely theoretical stand point.