Pseudo-alkene is a description of the transition state of an E2 elimination, which already has a partially formed carbon–carbon double bond (C=C) developing between the two carbons. It matters because the stability of this alkene-like transition state, like that of the alkene product, determines how easily the transition state is reached and therefore how fast the E2 reaction proceeds. This is why a more substituted, more stable double bond tends to form preferentially.

类烯烃是对 E2 消除过渡态的描述,该过渡态在两个碳之间已经有一个部分形成的碳碳双键(C=C)正在发展。它之所以重要,是因为这种类烯烃过渡态的稳定性(与烯烃产物的稳定性相似)决定到达该过渡态的难易,从而决定 E2 反应进行的快慢。这正是取代程度更高、更稳定的双键往往优先生成的原因。