The cyclohexene is a cyclic alkene or olefin whose molecular formula is C6H10. It consists of a colorless liquid, insoluble in water and miscible with many organic solvents. It is characterized by being flammable, and in nature it is usually found in coal tar.
Cyclohexene is synthesized by partial hydrogenation of benzene and by dehydration of the alcohol cyclohexanol; that is, a more oxidized form. Like other cycloalkenes, it undergoes electrophilic and free radical addition reactions; for example, the halogenation reaction.
This cyclic alkene (upper image) forms azeotropic mixtures (not separable by distillation), with lower alcohols and acetic acid. It is not very stable in prolonged storage, as it decomposes under the action of sunlight and ultraviolet radiation.
Cyclohexene is used as a solvent, and therefore has numerous applications, such as: stabilizer of high octane gasoline and for the extraction of oils.
But the most important thing is that cyclohexene serves as an intermediate and raw material for obtaining numerous highly useful compounds, including: cyclohexanone, adipic acid, maleic acid, cyclohexane, butadiene, cyclohexylcarboxylic acid, etc..
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The upper image shows the structure of cyclohexene with a model of spheres and bars. Note the six-carbon ring and the double bond, both unsaturations of the compound. From this perspective, it appears that the ring is flat; but it is not at all.
To begin with, the carbons of the double bond have sp hybridizationtwo, which gives them a trigonal plane geometry. Therefore, these two carbons, and those adjacent to them, are in the same plane; while the two carbons at the opposite end (to the double bond), are above and below said plane.
The image below perfectly illustrates what has just been explained.
Note that the black band is composed of four carbons: the two of the double bond, and the others adjacent to them. The exposed perspective is the one that would be obtained if a spectator placed his eye directly in front of the double bond. It can then be seen that a carbon is above and below this plane.
Since the cyclohexene molecule is not static, the two carbons will exchange: one will go down while the other will go up above the plane. So you would expect that molecule to behave.
Cyclohexene is a hydrocarbon, and therefore its intermolecular interactions are based on the London dispersion forces.
This is because the molecule is apolar, with no permanent dipole moment, and its molecular weight is the factor that contributes the most to keeping it cohesive in the liquid..
Likewise, the double bond increases the degree of interaction, since it cannot move with the same flexibility as that of the other carbons, and this favors the interaction between neighboring molecules. It is for this reason that cyclohexene has a slightly higher boiling point (83ºC) than that of cyclohexane (81ºC)..
Cyclohexene, tetrahydrobenzene.
82.146 g / mol.
Colorless liquid.
Sweet smell.
83 ºC at 760 mmHg.
-103.5 ºC.
-7 ºC (closed cup).
Practically insoluble (213 mg / L).
Miscible with ethanol, benzene, carbon tetrachloride, petroleum ether, and acetone. It is expected that it is capable of dissolving apolar compounds, such as some of the allotropes of carbon..
0.810 g / cm3 at 20ºC.
2.8 (relative to air taken as equal to 1).
89 mmHg at 25ºC.
244 ºC.
It decomposes in the presence of uranium salts, under the action of sunlight and ultraviolet radiation.
0.625 mPascal at 25 ºC.
3,751.7 kJ / mol at 25 ºC.
30.46 kJ / mol at 25 ºC.
26.26 mN / m.
May polymerize under certain conditions.
0.6 mg / m3.
1.4465 at 20 ºC.
7-8 to 20ºC.
Cyclohexene is not very stable during long-term storage. Exposure to light and air can lead to the production of peroxides. It is also incompatible with strong oxidizing agents..
-Cycloalkenes mainly undergo addition reactions, both electrophilic and with free radicals.
-Reacts with bromine to form 1,2-dibromocyclohexane.
-It oxidizes rapidly in the presence of potassium permanganate (KMnO4).
-It is capable of producing an epoxide (cyclohexene oxide) in the presence of peroxybenzoic acid.
Cyclohexene is produced by acid catalysis of cyclohexanol:
The symbol Δ represents the heat necessary to promote the exit of the OH group as a water molecule in an acid medium (-OHtwo+).
Cyclohexene is also produced by the partial hydrogenation of benzene; that is, two of its double bonds add a hydrogen molecule:
Although the reaction seems simple, it requires large pressures of Htwo and catalysts.
-It has utility as an organic solvent. In addition, it is a raw material for the production of adipic acid, adipic aldehyde, maleic acid, cyclohexane and cyclohexylcarboxylic acid..
-It is used in the production of cyclohexane chloride, a compound used as an intermediate in the manufacture of pharmaceutical products and rubber additive.
-Cyclohexene is also used in the synthesis of cyclohexanone, a raw material for the production of medicines, pesticides, perfumes and dyes..
-Cyclohexene is involved in the synthesis of aminocyclohexanol, a compound that is used as a surfactant and emulsifier.
-In addition, cyclohexene can be used for the laboratory preparation of butadiene. The latter compound is used in the manufacture of synthetic rubber, in the manufacture of automobile tires, and is also used in the manufacture of acrylic plastics.
-Cyclohexene is a raw material for the synthesis of lysine, phenol, polycycloolefin resin, and rubber additives.
-It is used as a stabilizer for high octane gasoline.
-Intervenes in the synthesis of waterproof coatings, crack resistant films, and bonding binders for coatings.
Cyclohexene is not a very toxic compound, but it can cause redness of the skin and eyes on contact. Inhalation can cause coughing and drowsiness. In addition, ingestion can cause drowsiness, shortness of breath and nausea..
Cyclohexene is poorly absorbed from the gastrointestinal tract, therefore serious systemic effects are not expected from ingestion. The maximum complication is its aspiration through the respiratory system, which can cause chemical pneumonia.
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