NOTES ON FULLY BENZENOID HYDROCARBONS AND THEIR CONSTANT-ISOMER SERIES

All-benzenoids (corresponding to fully benzenoid or total resonant sextet hydrocarbons) are treated. The possible values of n and s in an all-benzenoid formula C(n)H(s) are specified in general terms. Many other general formulations are reported, such as the general expressions of C(n)H(s) formulas for protrusive all-benzenoids, circular all-benzenoids, and extremal all-benzenoids. All these classes are precisely defined. The latter class (extremal all-benzenoids) contains exactly (if biphenyl is added) the members of constant-isomer series of all-benzenoids, the main subject of this work. Associated all-benzenoids give the link of these members to the members of the (ordinary) constant-isomer series of benzenoids. Supercircumscribing, a kind of an augmented circumscribing, is a crucial concept in these studies. Finally, the previously known numerical data for constant-isomer all-benzenoid series are supplemented.