Ethyl hexanoate (123-66-0) Physical and Chemical Properties
Ethyl hexanoate
A short-chain fatty acid ethyl ester used in flavor and fragrance formulations and as a specialty solvent or intermediate for formulation development and analytical work.
| CAS Number | 123-66-0 |
| Family | Short-chain fatty esters |
| Typical Form | Colorless liquid |
| Common Grades | EP, FCC, JP |
Ethyl hexanoate is a short-chain fatty acid ethyl ester (an aliphatic carboxylic acid ester) with a straight-chain C6 acyl portion bonded to an ethoxy group. Structurally it is a saturated, unbranched ester with formula C8H16O2; the functional ester group imparts a polar carbonyl/alkoxy moiety at one terminus while the remaining alkyl chain provides a nonpolar hydrocarbon tail. Electronic structure is dominated by the carbonyl \(>\)C=O dipole and the weaker electron-donating ethoxy substituent; no ionizable functional groups are present under normal aqueous conditions, so the compound is effectively neutral (formal charge 0) and nonacidic at ambient pH.
Physicochemical behavior is typical of small alkyl esters: moderate lipophilicity, low aqueous solubility, volatility sufficient for aroma/flavor applications, and susceptibility to base- or acid-catalyzed hydrolysis (saponification/transesterification) under strongly alkaline or acidic conditions. Hydrogen-bonding capacity is limited to two acceptor sites (carbonyl oxygen and alkoxy oxygen); there are no hydrogen-bond donors. The balance of polar (ester) and apolar (C8 alkyl) domains yields an XLogP indicative of appreciable partitioning into nonpolar phases and oils, which explains its common use as a flavor and fragrance ingredient.
Commercially, this material is encountered in food- and fragrance-grade preparations and in technical solvents/formulations for flavor/fragrance manufacture and agrochemical use. Common commercial grades reported for this substance include: EP, FCC, JP.
Basic Physical Properties
Density
Reported values for density are 0.867-0.871 (reported without explicit units in the cited data). The value range is consistent with liquid alkyl esters of similar chain length and reflects a bulk density slightly less than water; small variations are expected with temperature and purity.
Melting Point
Melting point: \(-67.5\,^{\circ}\mathrm{C}\). This low solidification temperature is consistent with a volatile, low-molecular-weight ester and explains its liquid state at ambient temperatures.
Boiling Point
Boiling point: \(166.00\) to \(168.00\,^{\circ}\mathrm{C}\) at \(760.00\,\mathrm{mmHg}\). The relatively moderate boiling point and vapor pressure make the compound volatile enough to be perceived as an odorant while still amenable to distillative purification in laboratory and industrial settings.
Vapor Pressure
Vapor pressure reported as \(1.56\,\mathrm{mmHg}\) (presumably at or near ambient temperature in the reported measurement context). The vapor pressure is consistent with the observed volatility and the compound’s use in flavor and fragrance applications.
Flash Point
No experimentally established value for this property is available in the current data context.
Chemical Properties
Solubility and Phase Behavior
Aqueous solubility is low: \(0.629\,\mathrm{mg}\,\mathrm{mL}^{-1}\) at \(25\,^{\circ}\mathrm{C}\). The compound is reported as insoluble in water and glycerol but soluble in most fixed oils and in propylene glycol; it is also miscible to a limited extent in ethanol (example: 1 mL in 2 mL of 70% ethanol reported). The combination of low water solubility and appreciable oil solubility makes ethyl hexanoate useful as an ingredient in oil-phase flavor and fragrance formulations and as a flavoring solvent for oil-based matrices.
Phase behavior: liquid at ambient temperature with low freezing point and moderate volatility; will form a separate organic phase in aqueous systems at concentrations near saturation and is readily extracted into nonpolar solvents.
Reactivity and Stability
Ethyl hexanoate is chemically stable under neutral, non-catalytic conditions but undergoes hydrolysis under acidic or basic conditions to yield hexanoic (caproic) acid and ethanol; base-catalyzed saponification leads to the corresponding carboxylate salt. It can participate in transesterification in the presence of alcohols and acid/base catalysts. As an organic ester, it is combustible and should be kept away from ignition sources and strong oxidizers. Photochemical oxidation in air is not a dominant degradation pathway for short exposures, but prolonged exposure to light and heat can promote slow oxidative degradation. Storage under cool, dark conditions in tightly closed containers reduces the risk of decomposition and loss by evaporation.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
No experimentally established value for this property is available in the current data context.
Molecular Parameters
Molecular Weight and Formula
Molecular formula: C8H16O2.
Molecular weight: 144.21 (reported).
Additional mass descriptors: Exact/monoisotopic mass \(144.115029749\).
LogP and Polarity
XLogP (reported) = 2.4, indicating moderate lipophilicity and a tendency to partition into organic phases rather than aqueous media. Topological polar surface area (TPSA) = 26.3, consistent with a single ester moiety imparting limited polar surface area. Hydrogen-bond donor count = 0; hydrogen-bond acceptor count = 2.
Structural Features
SMILES: CCCCC C(=O)OCC (reported as "CCCCCC(=O)OCC").
InChI: InChI=1S/C8H16O2/c1-3-5-6-7-8(9)10-4-2/h3-7H2,1-2H3.
InChIKey: SHZIWNPUGXLXDT-UHFFFAOYSA-N.
Structural summary: a linear hexanoyl chain (n-hexanoate/caproate) esterified with ethanol. No stereocenters are present (defined stereocenter count = 0). Rotatable bond count = 6, reflecting a flexible alkyl tail and the single ester linkage; complexity reported as 89.3. The ester carbonyl provides the principal site for nucleophilic attack in hydrolysis/transesterification reactions.
Identifiers and Synonyms
Registry Numbers and Codes
CAS number: 123-66-0.
Deprecated CAS: 8068-81-3 (reported as deprecated).
EC number: 204-640-3.
UNII: FLO6YR1SHT.
ChEBI: CHEBI:86055.
DSSTox Substance ID: DTXSID3021980.
FEMA Number: 2439.
NSC Number: 8882.
Additional registry strings reported in source annotations include various catalogue and internal identifiers; the primary regulatory CAS is shown above.
Synonyms and Structural Names
Reported synonyms include (selected, as provided): ethyl hexanoate; hexanoic acid ethyl ester; ethyl caproate; ethyl capronate; ethyl n-hexanoate; caproic acid ethyl ester; ethyl hexoate; ethyl capronate (natural); Ethyl ester of hexanoic acid.
Industrial and Commercial Applications
Representative Uses and Industry Sectors
Ethyl hexanoate is widely used as a flavoring and fragrance ingredient, imparting fruity, apple/banana/overripe fruit and brandy-like notes; it is employed in artificial fruit flavors and formulation of aroma blends. It is permitted for use as a flavoring agent and has recorded use in animal feed flavoring. The substance may also be used as an inert ingredient in certain non-food pesticide formulations and appears in consumer products where fragrance or solvent properties are required.
Role in Synthesis or Formulations
In formulation chemistry it functions as an aroma constituent, a solvent for oil-phase ingredients, and a reactive intermediate in ester interchange or transesterification processes for flavor/fragrance synthesis. Its miscibility with common formulation solvents such as ethanol and propylene glycol facilitates incorporation into both aqueous-alcoholic and oil-based vehicle systems.
Safety and Handling Overview
Acute and Occupational Toxicity
Signal word reported: Warning. GHS hazard statements include H226: flammable liquid and vapor; some notifications also list aquatic hazards H401 and H411 (toxic to aquatic life and with long-lasting effects). Reported hazard notes indicate the compound is a moderate skin irritant and a strong eye irritant in material safety data statements; it is also associated with solvent-type acute effects in high exposures (noted as “acute solvent syndrome” in toxicology summaries). No specific numeric LD50 or occupational exposure limits are available in the current data context.
For occupational settings, control measures should focus on minimizing inhalation and dermal exposure: local exhaust ventilation, closed handling systems where feasible, and selectable respiratory protection when ventilation is inadequate. Use chemical-resistant gloves and eye protection to prevent skin and eye contact. Avoid release to aquatic environments.
Storage and Handling Considerations
Store in a cool, well-ventilated area away from sources of ignition and strong oxidizing agents. Keep containers tightly closed to prevent evaporation and ingress of moisture or contaminants. Ground and bond containers during transfer to avoid static discharge. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
For disposal and spill response: absorb small spills with inert material and collect for appropriate disposal; prevent product from entering drains and watercourses.
