| The nylon-making plantat Flixborough, England, was devastated in 1974. Cyclohexane exploded as it was being oxidized (one stage in the synthesis of nylon 6). Like other alkanes, cyclohexane can be oxidized completely to carbon dioxide and water. Such a reaction releases a large amount of energy if it is not controlled.
Ethene (ethylene, C2H4)
| Propene (propylene, C3H6)
|
| PropadieneiCjH,,)
| c = c
| H\ ! /H
H—C —C = C
|
| c=c=c
| l-butene(C4H8)
| c/s-2-butene (C4HS)
|
1,3-butadiene(C4H6)
| \ 1 T /
H—C—C—C=C
| \ i T /H
H-C—C=C—C-H
|
| H H ^ H
H\ 1 1 /
| rrans-2-butene (C„H8)
| 2-methylbutene (C4H8)
|
| 1.2-butadiene(C4H.,)
| H\ " /"
H — C—C=C—C—H
| H /H H—C—C=C,/ 1, XH
|
| C=C=C—C —H
| Alkenesare unsaturated aliphatic hydrocarbons with one carbon-carbon double bond. The first few members of the series are illustrated {above left). Ethene (pink box) and propene (pale blue box) each have only one possible structure. However, butene has four (pale green panels). Alka-dienes have two carbon-carbon double bonds. The first few members are illustrated above right. Propadiene (grey box) has only one possible form, whereas butadiene (dark green box) has two.
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Unsaturated
Aliphatic
Hydrocarbons
Unsaturated aliphatic hydrocarbons are the building blocks of the organic chemical industry. The term "unsaturated" indicates that the carbon atoms are not saturated (filled) with the maximum number of hydrogen atoms. Four bonds are possible for each carbon atom. Saturated hydrocarbons bond with four other atoms (a combination of carbon and hydrogen
atoms). Unsaturated hydrocarbons contain at least one carbon-carbon multiple bond. A double bond leaves room for only two other bonds with hydrogen or carbon. A triple bond makes possible only one other bond with hydrogen or carbon.
Compounds with double bonds are also commonly known as alkenes or olefins. By far, the most important alkene is ethene (ethylene), followed by propene (propylene), and butadiene. Ethyne (acetylene) is the most important alkyne, as compounds with a triple carbon-carbon bond are called.
Compounds with two or more multiple bonds are termed polyunsaturated (a characteristic of many natural fats and oils). Where there are two double bonds in an alkene, they may be differently arranged. The color of many organic compounds depends on the arrangement of double bonds in the molecule.
Date: 2015-12-11; view: 1785
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