简单的环丁二烯是极其不稳定的化合物.除非在非常低的温度下将其保存在基质中(使环丁二烯分子彼此远离),否则它的寿命是极短的(通过Diels—Aldler反应而聚合).有人预言,它可能是已知双烯中最活泼的物质.由于这个原因,人们试图从它的结构方面去寻找引起这些现象的本质.关于环丁二烯结构的主要问题是它为什么如此不稳定,是正方形(D_(4h))三线态呢还是长方形(D_(2h))单线态呢?下面我们就这些问题作一探讨. Simple cyclobutadiene is a very unstable compound and its life span is extremely short unless it is stored in a matrix at very low temperatures (leaving the cyclobutadiene molecules away from each other (by Diels-Aldler Reaction.) It has been predicted that it may be the most active substance in known dienes. For this reason, one seeks to find from its structure the nature of these phenomena. The major problem with cyclobutadiene structures is that Why it is so unstable, is the square (D_ (4h)) triplet or rectangular (D_ (2h)) singlet state? Here we discuss these issues.