3-Ethynylcyclopropene: a highly suspicious crystal structure

Abstract

High level ab initio structures for 3-ethynylcyclopropene contain a typical cyclopropene C[double bond, length half m-dash]C double bond of 1.296 Å, in sharp contrast to a recent X-ray structure in which the C[double bond, length half m-dash]C double bond (1.255(2) Å) is purported to be the shortest yet observed among all hydrocarbons.

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