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Cyclobutene is an organic compound with the chemical formula C 4 H 6. It is a cycloalkene. It is a colorless gas that easily condenses. It is of interest in research ...
In organic chemistry, a cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms and either one or more double bonds, but has no aromatic character. Some cycloalkenes, such as cyclobutene and cyclopentene , can be used as monomers to produce polymer chains. [ 1 ]
The compound is the prototypical antiaromatic hydrocarbon with 4 pi electrons (or π electrons). It is the smallest [n]-annulene ([4]-annulene).Its rectangular structure is the result of a pseudo [3] - (or second order) Jahn–Teller effect, which distorts the molecule and lowers its symmetry, converting the triplet to a singlet ground state. [4]
The lowest triplet state of an annulene is, according to Baird's rule, aromatic when it has 4n π-electrons and antiaromatic when the π-electron count is 4n + 2, where n is any positive integer. This trend is opposite to that predicted by Hückel's rule for the ground state , which is usually the lowest singlet state (S 0 ).
For example, the aromatic species 1 can be reduced to 2 with a relatively small penalty for forming an antiaromatic system. The antiaromatic 2 does revert to the aromatic species 1 over time by reacting with oxygen in the air because the aromaticity is preferred. [15] The loss of antiaromaticity can sometimes be the driving force of a reaction.
The discovery that [18]annulene possesses a number of key properties associated with other aromatic molecules was an important development in the understanding of aromaticity as a chemical concept. In the related annulynes , one double bond is replaced by a triple bond .
In the conrotatory ring opening of cyclobutene, there are two electrons moving suprafacially (on the pi bond) and two moving antarafacially (on the sigma bond). This means there is one 4 q + 2 suprafacial system and no 4r antarafacial system; thus, the conrotatory process is thermally allowed by the Woodward–Hoffmann rules.
Butene, also known as butylene, is an alkene with the formula C 4 H 8.The word butene may refer to any of the individual compounds. They are colourless gases that are present in crude oil as a minor constituent in quantities that are too small for viable extraction.