2-Ethylhexanoic acid

2-Ethylhexanoic acid (2-EHA), commonly known as octoic acid,^[2] is the organic compound with the formula CH₃(CH₂)₃CH(C₂H₅)CO₂H. It is a carboxylic acid that is widely used to prepare lipophilic metal derivatives that are soluble in nonpolar organic solvents. 2-Ethylhexanoic acid is a colorless viscous oil. It is supplied as a racemic mixture.

2-Ethylhexanoic acid

Skeletal formula of 2-ethylhexanoic acid
Names
Preferred IUPAC name 2-Ethylhexanoic acid[1]
Identifiers
CAS Number	149-57-5 Y 72377-05-0 S enantiomer N 56006-48-5 R enantiomer N
3D model (JSmol)	Interactive image
Beilstein Reference	1750468
ChEMBL	ChEMBL1162485 Y ChEMBL1162487 N ChEMBL1162486 N
ChemSpider	8373 Y 70431 R N 119200 S N
ECHA InfoCard	100.005.222
EC Number	205-743-6
MeSH	2-ethylhexanoic+acid
PubChem CID	8697 78052 R 135309 S
RTECS number	MO7700000
UNII	01MU2J7VVZ Y
CompTox Dashboard (EPA)	DTXSID9025293
InChI InChI=1S/C8H16O2/c1-3-5-6-7(4-2)8(9)10/h7H,3-6H2,1-2H3,(H,9,10) Y Key: OBETXYAYXDNJHR-UHFFFAOYSA-N Y
SMILES CCCCC(CC)C(O)=O
Properties
Chemical formula	C8H16O2
Molar mass	144.214 g·mol−1
Appearance	Colorless liquid
Density	903 mg mL−1
Melting point	−59.00 °C; −74.20 °F; 214.15 K
Boiling point	228.1 °C; 442.5 °F; 501.2 K
log P	2.579
Vapor pressure	<1 Pa (at 25 °C)
Acidity (pKa)	4.819
Basicity (pKb)	9.178
Refractive index (nD)	1.425
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−635.1 kJ mol−1
Std enthalpy of combustion (ΔcH⦵298)	−4.8013 – 4.7979 MJ mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H312, H318, H361
Precautionary statements	P280, P305+P351+P338
Flash point	114 °C (237 °F; 387 K)
Autoignition temperature	371 °C (700 °F; 644 K)
Explosive limits	0.9–6.7%
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1.142 g kg−1 (dermal, rabit) 3 g kg−1 (oral, rat)
Related compounds
Related compounds	2-Methylhexane 3-Methylhexane Valnoctamide 2-Methylheptane 3-Methylheptane 2-Ethylhexanol Valproic acid Propylheptyl alcohol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Production

2-Ethylhexanoic acid is produced industrially from propylene, which is hydroformylated to give butyraldehyde. Aldol condensation of the aldehyde gives 2-ethylhexenal, which is hydrogenated to give 2-ethylhexanal. Oxidation of this aldehyde gives the carboxylic acid.^[3]

Metal ethylhexanoates

65% Solution of cobalt(II) bis(2-ethylhexanoate) in mineral spirits, tilted vial to illustrate color and viscosity.

2-Ethylhexanoic acid forms compounds with metal cations that have stoichiometry as metal acetates. These ethylhexanoate complexes are used in organic and industrial chemical synthesis.^[4] They function as catalysts in polymerizations as well as for oxidation reactions as "oil drying agents."^[5] They are highly soluble in nonpolar solvents. These metal complexes are often described as salts. They are, however, not ionic but charge-neutral coordination complexes. Their structures are akin to the corresponding acetates.

Examples of metal ethylhexanoates

• Hydroxyl aluminium bis(2-ethylhexanoate), used as a thickener
• Tin(II) ethylhexanoate (CAS# 301-10-0), a catalyst for polylactide and poly(lactic-co-glycolic acid).^[6]
• Cobalt(II) ethylhexanoate (CAS# 136-52-7), a drier for alkyd resins
• Nickel(II) ethylhexanoate (CAS# 4454-16-4)^[7]

Regulations

2-Ethylhexanoic acid is banned in the EU for use in cosmetics.^[8]

See also

• 2-Ethylhexanol