Bond distances cyclobutadiene derivative

High level molecular orbital calculations of cyclobutadiene itself and experimen tally measured bond distances of a stable highly substituted derivative both reveal a pat tern of alternating short and long bonds characteristic of a rectangular rather than square geometry... 

Structural studies of cyclobutadiene and some of its derivatives reveal a pattern of alternating single and double bonds and a rectangular, rather than a square, shape. Bond distances in a stable, highly substituted derivative of cyclobutadiene illustrate this pattern of alternating short and long ring bonds. 

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