Herein, it is shown that, at the Hückel level, 4N rings may stabilize or destabilize even alternant hydrocarbons. Further, 4N + 2 rings may stabilize or destabilize even alternant hydrocarbons. Some structural engineering techniques are presented that permit rationally selected structural changes to alter expected kinetic stabilities for neutral, even alternant hydrocarbons. A related set of non-alternant hydrocarbons (pseudoalternant hydrocarbons) are described and calculated kinetic stability trends are described for them.