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Alkenes
ОглавлениеAn alkene (olefin) is an unsaturated chemical compound containing at least one carbon-to-carbon double bond (Table A-18). The simplest acyclic alkenes, with only one double bond and no other functional groups, form a homologous series of hydrocarbons with the general formula CnH2n. The simplest alkene is ethylene (C2H4), which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry).
The physical properties of alkenes are comparable with those of alkanes (aliphatic hydrocarbons). The physical state depends on molecular mass (gases from ethylene to butene - liquids from pentene onwards). The simplest alkenes, ethylene, propylene (propene), and butylene (butene) are gases. Linear alkenes of approximately 5 to 16 carbons are liquids, and higher molecular weight alkenes are waxy solids. Alkenes are more reactive than alkanes due to the presence of a carbon-carbon pi-bond (double bond). The majority of the reactions of alkenes involve the rupture of this pi bond, forming new single bonds.
Table A-18 Physical properties of selected olefins.
| Olefin | Melting point, °C | Boiling point, °C | Density, g/ml @20 °C |
|---|---|---|---|
| Ethylene | -169 | -102 | |
| Propylene | -158 | -48 | |
| 1-Butene | -6.5 | ||
| 1-Pentene | 30 | ||
| 1-Hexene | -138 | 63.5 | 0.643 |
| 1-Heptene | -119 | 93 | 0.675 |
| 1-Octene | -104 | 122.5 | 0.698 |
| 1-Nonene | 146 | 0.716 | |
| 1-Decene | -87 | 171 | 0.731 |
| Cis-2-butene | -139 | 4 | 0.743 |
| Trans-2-butene | -106 | 1 | |
| Isobutylene | -141 | -7 | |
| Cis-2-pentene | -151 | 37 | |
| 2-Methyl-2-butene | -123 | 39 | 0.655 |
| 2,3-Dimethyl-2-butene | -74 | 73 | 0.660 |
| Cyclopentene | -93 | 46 | 0.705 |
| Cyclohexene | -104 | 83 | 0.774 |
| 1,3-Cyclopentadiene | -85 | 42 | 0.810 |
| 1,3-Cyclohexadiene | -49 | 87 | 0.798 |
| 0.847 |
Alkenes serve as a feedstock for the petrochemical industry because they can participate in a wide variety of reactions.
The simplest acyclic alkenes, with only one double bond and no other functional groups, form a homologous series of hydrocarbons with the general formula CnH2n.
The physical properties of alkene derivatives are comparable with those of alkane derivatives (aliphatic hydrocarbon derivatives). The physical state depends on molecular mass (gases from ethylene to butene and liquids from pentene onwards). The simplest alkenes, ethylene, propylene (propene), and butylene (butene) are gases. Linear alkenes of approximately 5 to 16 carbons are liquids, and higher molecular weight alkenes are waxy solids.
Alkene derivatives are more reactive than alkane derivatives due to the presence of a carbon-carbon pi-bond (double bond). The majority of the reactions of alkenes involve the rupture of this pi bond, forming new single bonds.
