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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 ...
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]
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.
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 ]
A newer, more efficient preparation of cyclobutanone was found by P. Lipp and R. Köster in which a solution of diazomethane in diethyl ether is reacted with ketene. [5] This reaction is based on a ring expansion of the cyclopropanone intermediate initially formed, wherein molecular nitrogen is split off:
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Unsaturated compounds generally carry out typical addition reactions that are not possible with saturated compounds such as alkanes. A saturated organic compound has only single bonds between carbon atoms. An important class of saturated compounds are the alkanes. Many saturated compounds have functional groups, e.g., alcohols.
However, imidazol-2-ylidenes and triazol-5-ylidenes are thermodynamically stable and do not dimerise, and have been stored in solution in the absence of water and air for years. This is presumably due to the aromatic nature of these carbenes, which is lost upon dimerisation. In fact imidazol-2-ylidenes are so thermodynamically stable that only ...