1-Octene
1-Octene is an unsaturated hydrocarbon and a linear alpha-olefin with the chemical formula C₈H₁₆, featuring a terminal carbon-carbon double bond at the 1-position, which distinguishes it from other octene isomers.[1] It appears as a clear, colorless liquid with a gasoline-like odor, has a molecular weight of 112.21 g/mol, a melting point of -101 °C, a boiling point of 122–123 °C, and a density of 0.715 g/mL at 25 °C.[1] Insoluble in water but miscible with organic solvents such as ether, alcohol, and acetone, it is highly flammable with a flash point of 10 °C (closed cup) and exhibits reactivity typical of alkenes, including potential exothermic polymerization or reactions with strong oxidizers.[1][2] Industrially, 1-octene is primarily produced through the selective oligomerization of ethylene, specifically tetramerization, using chromium-based catalysts to yield linear alpha-olefins with high selectivity.[3] This process, commercialized by companies like Phillips and Sasol, generates 1-octene as a key product alongside other olefins like 1-hexene, enabling large-scale production for downstream applications.[3][4] The compound's most significant uses revolve around its role as a comonomer in the production of polyethylene, particularly linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE), where it improves polymer properties such as flexibility and impact strength.[1][5] Additionally, 1-octene serves as a feedstock for polyalphaolefins (PAOs) in synthetic lubricants, offering high viscosity indices and thermal stability, and is employed in the synthesis of surfactants, plasticizers, and oxo-alcohols via hydroformylation.[5][6] Its low toxicity and mild irritant effects make it suitable for these industrial applications, though handling requires precautions due to flammability.[2]Structure and Properties
Molecular Structure
1-Octene has the molecular formula C₈H₁₆ and the systematic IUPAC name oct-1-ene.[2] Its structural formula is CH₂=CH(CH₂)₅CH₃, representing a linear chain of eight carbon atoms with a carbon-carbon double bond at the terminal position.[7] This configuration classifies 1-octene as an alpha-olefin, where the double bond is located between the first and second carbon atoms, distinguishing it from internal olefins.[8] The IUPAC nomenclature for 1-octene follows the standard rules for alkenes, which involve identifying the longest continuous carbon chain containing the double bond and numbering it from the end that gives the lowest number to the double bond position, resulting in the suffix "-ene" with the locant "1". In the molecular structure of 1-octene, the carbons involved in the double bond (C1 and C2) exhibit sp² hybridization, leading to a trigonal planar geometry around these atoms with bond angles of approximately 120°.[9] The C=C double bond consists of a σ bond and a π bond, with a typical bond length of about 1.33 Å, while the adjacent C-C single bonds have lengths of approximately 1.54 Å.[9] 1-Octene exists among positional isomers of octene, such as 2-octene where the double bond is between carbons 2 and 3, but its terminal double bond position imparts unique reactivity, particularly in addition reactions and polymerization processes due to the accessibility of the unsubstituted vinyl group.Physical Properties
1-Octene is a colorless, clear liquid at room temperature, exhibiting a mild hydrocarbon odor.[2][10] Its density is 0.715 g/cm³ at 20 °C, which is relatively low due to its linear molecular structure compared to branched octene isomers.[11] The melting point is −101.7 °C, and the boiling point is 121–123 °C at 1 atm.[1][12] The flash point is 10 °C (closed cup), indicating high flammability under standard conditions.[2] 1-Octene is insoluble in water, with a solubility of 0.004 g/L at 25 °C, but it is miscible with organic solvents such as ethanol and ether.[13][2] The refractive index is 1.408–1.409 at 20 °C.[1] Its vapor pressure is 15 mmHg (2 kPa) at 20 °C, and the autoignition temperature is 220 °C.[13][14] Key thermodynamic data include a standard heat of combustion of Δ_cH° = −5312.9 kJ/mol for the liquid phase and a dipole moment of μ = 0.30 D.[15][16]| Property | Value | Conditions |
|---|---|---|
| Density | 0.715 g/cm³ | 20 °C |
| Melting point | −101.7 °C | - |
| Boiling point | 121–123 °C | 1 atm |
| Flash point | 10 °C | Closed cup |
| Refractive index | 1.408–1.409 | 20 °C |
| Vapor pressure | 15 mmHg | 20 °C |
| Autoignition temperature | 220 °C | - |
| Heat of combustion | −5312.9 kJ/mol | Liquid, standard |
| Dipole moment | 0.30 D | - |