Undecane (11-10-8) Physical and Chemical Properties
Undecane
Straight-chain C11 alkane used as a low‑polarity solvent and hydrocarbon intermediate with low water solubility and a relatively high boiling point.
| CAS Number | 11-10-8 |
| Family | Aliphatic hydrocarbon (alkane) |
| Typical Form | Colorless liquid |
| Common Grades | BP, EP, JP, USP |
Undecane is a straight-chain saturated hydrocarbon (n-alkane) of the normal paraffin series with molecular formula \(C_{11}H_{24}\). Structurally it is an unbranched chain of eleven methylene units terminated by methyl groups (SMILES: CCCCCCCCCCC). The electronic structure is characterized by saturated sp^3 C–H and C–C bonds with no heteroatoms, resulting in negligible polarity, zero hydrogen-bond donor/acceptor capacity, and a topological polar surface area of \(0\). The lack of functional groups makes undecane chemically inert to hydrolysis and nucleophilic substitution under neutral conditions, while rendering it susceptible to radical-mediated oxidation and combustion processes.
Physicochemically, undecane is a nonpolar, hydrophobic liquid at ambient temperature with low water solubility and significant lipophilicity (\(XLogP = 5.6\)). It partitions strongly into organic phases and biological lipids, which governs its environmental fate (volatilization, adsorption to organic matter) and biodistribution (high fat:blood partitioning). In the atmosphere it is degraded primarily by reaction with hydroxyl radicals; thermal and oxidative degradation produce aliphatic oxidation products and ultimately carbon oxides under combustion. Industrially, undecane is used as a solvent and process intermediate and occurs as a component of fuel streams; it is also employed as a reference/analytical standard and appears in fragrance ingredient lists for certain formulations.
Common commercial grades reported for this substance include: BP, EP, JP, USP.
Physical Properties
Density and Phase
Undecane is a clear, colorless liquid at ambient conditions and is less dense than water; it will float on water. Experimental density values reported include \(0.74017\) at \(68\,^\circ\mathrm{F}\) (NTP, 1992) and \(0.7402\,\mathrm{g\,cm^{-3}}\) at \(20\,^\circ\mathrm{C}\). Vapor density is reported as \(5.4\) (Air = 1), indicating vapor heavier than air that can collect in low or confined areas.
Melting Point
Reported melting/solidification values are: \(-14.1\,^\circ\mathrm{F}\) (NTP, 1992), \(-25.54\,^\circ\mathrm{C}\), and \(-26.00\,^\circ\mathrm{C}\) at \(760.00\) mm Hg. These values indicate that undecane remains liquid well below typical ambient temperatures.
Boiling Point
Experimental boiling points are reported as \(384.6\,^\circ\mathrm{F}\) at \(760\) mmHg (NTP, 1992), approximately \(385\,^\circ\mathrm{F}\), and \(195.9\,^\circ\mathrm{C}\). A measured range is \(195.00\) to \(198.00\,^\circ\mathrm{C}\) at \(760.00\) mm Hg. These values reflect the expected moderate vapor pressure of an \(n\)-alkane of this chain length.
Vapor Pressure
Vapor pressure data: \(0.41\) mmHg (reported) and specifically \(0.412\,\mathrm{mmHg}\) at \(25\,^\circ\mathrm{C}\). This vapor pressure is consistent with significant volatility at elevated temperatures and explains rapid volatilization from water and moist soils under environmental release scenarios.
Viscosity
Dynamic viscosity is reported as \(1.098\,\mathrm{mPa\,s}\) at \(25\,^\circ\mathrm{C}\), consistent with low-viscosity aliphatic hydrocarbons in the C10–C12 range.
Chemical Properties
Flammability and Combustion
Undecane is a flammable, combustible hydrocarbon. Flash point values reported include \(149\,^\circ\mathrm{F}\) (NFPA, 2010) and a closed-cup value of \(62.0\,^\circ\mathrm{C}\) (\(143.6\,^\circ\mathrm{F}\)); an open-cup value of \(149\,^\circ\mathrm{F}\) (\(65\,^\circ\mathrm{C}\)) is also cited. GHS hazard statements associated with undecane commonly include: H226 (Flammable liquid and vapor), H304 (May be fatal if swallowed and enters airways), and H335 (May cause respiratory irritation). Combustion yields carbon oxides and, under incomplete combustion, irritant or toxic fumes; vapors are heavier than air and can form explosive mixtures with air and travel to ignition sources.
Reactivity and Typical Transformations
As a saturated aliphatic hydrocarbon, undecane is broadly chemically unreactive toward acids, bases, and many common reagents under ambient conditions. The principal chemical transformations of practical relevance are: - Radical oxidation (atmospheric degradation): the vapor-phase reaction with hydroxyl radicals has an experimentally determined rate constant of \(1.32\times10^{-11}\,\mathrm{cm^{3}\,molecule^{-1}\,s^{-1}}\) at \(25\,^\circ\mathrm{C}\), corresponding to an atmospheric half-life on the order of tens of hours under typical OH concentrations. - Biotransformation: metabolic hydroxylation (primarily at secondary carbon positions) yielding alcohols and subsequent oxidation to ketones; animal studies indicate 2- and 3-position alcohols and ketones as common metabolites. - Thermal decomposition and combustion: produces CO, CO2 and irritant combustion products; heating to decomposition emits acrid smoke and irritating fumes.
Undecane does not undergo hydrolysis and is not susceptible to nucleophilic displacement due to absence of functional groups. Heat of vaporization values reported include \(56.58\,\mathrm{kJ\,mol^{-1}}\) at \(25\,^\circ\mathrm{C}\) and \(41.91\,\mathrm{kJ\,mol^{-1}}\) at \(195.9\,^\circ\mathrm{C}\).
Identifiers and Synonyms
Registry Numbers and Codes
- CAS (provided identifier): 11-10-8
- EC number: 214-300-6
- UN number / DOT ID: UN2330 (Undecane)
- UN Number (alternative format in sources): 2330 (UNDECANE)
- UNII: JV0QT00NUE
- ChEBI: CHEBI:46342
- InChIKey: RSJKGSCJYJTIGS-UHFFFAOYSA-N
- InChI: InChI=1S/C11H24/c1-3-5-7-9-11-10-8-6-4-2/h3-11H2,1-2H3
- SMILES: CCCCCCCCCCC
- Molecular formula: \(C_{11}H_{24}\)
- Molecular weight: \(156.31\)
- XLogP: \(5.6\)
(Identifiers listed above are drawn from available registry and computed descriptor records.)
Synonyms and Structural Names
Common synonyms and name variants reported include: undecane; N-UNDECANE; n-undecane; hendecane; n-hendecane; n-undecan; UNDECANE, N-. These reflect trivial and systematic naming conventions for the linear C11 alkane.
Industrial and Commercial Applications
Use as Solvent or Fuel Component
Undecane is used industrially as a component of gasoline and jet/petroleum distillates and as a nonpolar solvent. Its solvent properties (nonpolar, low dielectric) make it suitable for applications such as inks, degreasing formulations, and as a process solvent in hydrocarbon-based manufacturing. It also serves as a feedstock/intermediate in the production of linear alkylbenzenes, certain detergent alcohols, and other higher-value petrochemical derivatives.
Representative Use Scenarios
Representative scenarios include: - Component of fuel blends and formulations where C11 hydrocarbons contribute to volatility and combustion properties. - Solvent for printing inks and degreasing operations where nonpolar solvency and rapid evaporation are required. - Distillation chaser and fractionation component during refining or laboratory-scale separations. - Chemical intermediate in the manufacture of surfactants and alkylation chemistry. Commercial supply is offered in various technical and analytical grades (reported grades include 95%, 99%, and research grades).
Safety and Handling Overview
Flammability Hazards
Undecane is a flammable/combustible liquid with low flash point values that require strict elimination of ignition sources. Vapors are heavier than air and can collect in low areas, creating vapor explosion and flash-back hazards. Firefighting guidance for similar nonpolar flammable liquids applies: use foam, dry chemical, CO2 or water spray for small fires; for large fires use alcohol-resistant foam or water spray from a safe distance and cool containers. Combustion can produce carbon oxides and irritating fumes.
For personnel and emergency planning, undecane carries aspiration hazard concerns (H304) — ingestion with risk of aspiration into the lungs can be fatal — and may cause respiratory tract and mucous membrane irritation on inhalation.
Storage and Handling Considerations
Storage and handling recommendations for undecane reflect its classification as a flammable hydrocarbon: - Store in tightly closed containers in a cool, dry, well-ventilated area away from oxidizing agents and strong acids/bases. Observe storage-class conventions for flammable liquids. - Avoid accumulation of electrostatic charge; ground and bond equipment during transfer and processing. - Use explosion-proof electrical equipment and non-sparking tools in handling areas. - Implement engineering controls (local exhaust ventilation) to limit airborne concentrations; monitor confined-space atmospheres where vapors may accumulate. - Personal protective equipment: chemical-resistant gloves, eye/face protection, and protective clothing for skin contact. For emergency response and firefighting, use positive-pressure self-contained breathing apparatus (SCBA) and turnout gear with limited chemical protection. - In case of spills, eliminate ignition sources, dike and absorb with noncombustible material, and use clean, non-sparking tools for recovery; prevent entry to sewers and waterways and manage run-off.
Undecane is readily biodegradable under aerobic conditions but is lipophilic and may bioconcentrate; environmental releases should be contained and remediated. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
