Butyric acid (C4H8O2): structure, properties and hazards

Names and identifiers

IUPAC name: butanoic acid
Synonyms: butanoic acid, C4:0, n-Butyric acid
+ 36 more
n-Butanoic acid, propylformic acid, ethylacetic acid, 1-propanecarboxylic acid, Butanic acid, 1-Butyric acid, Buttersaeure, Kyselina maselna, FEMA No. 2221, Propanecarboxylic acid, 1-butanoic acid, FEMA Number 2221, Butyricum acidum, NORMAL BUTYRIC ACID, DTXSID8021515, NSC-8415, 40UIR9Q29H, NSC8415, DTXCID401515, CHEBI:30772, Acid, Butanoic, Tetranoic Acid, Acid, Butyric, Butyrate, Magnesium, fatty acid 4:0, Dibutyrate, Magnesium, RefChem:6399, CHEBI:140601, 203-532-3, Butyric acid (natural), Buttersaeure [German], Kyselina maselna [Czech], fattyacids, MFCD00002814, CCRIS 6552, HSDB 940
Molecular formula: C₄H₈O₂
Empirical formula: C₂H₄O
Molecular weight: 88.11 g/mol
Exact mass: 88.05243
CAS number: 107-92-6
PubChem CID: 264
Canonical SMILES: CCCC(=O)O
Isomeric SMILES: CCCC(=O)O
InChI: InChI=1S/C4H8O2/c1-2-3-4(5)6/h2-3H2,1H3,(H,5,6)
InChIKey: FERIUCNNQQJTOY-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Colorless liquid[4]
4 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Butyric acid appears as a colorless liquid with a penetrating and unpleasant odor. Flash point 170 °F. Corrosive to metals and tissue. Density 8.0 lb /gal. [1] CAMEO Chemicals
– Liquid; CBI [2] EPA Chemical Data Reporting (CDR)
– COLOURLESS OILY LIQUID WITH CHARACTERISTIC ODOUR. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown Colorless liquid [4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 14th Edition. John Wiley & Sons, Inc. New York, NY 2001., p. 183
Odor: Penetrating and obnoxious odor[4]
Melting point: -7.9 °C (17.8 °F, NTP 1992)[1]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
−7.9 °Cshown 17.8 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
−7.9 °C -7.9 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−5.1 °C -5.1 °C [5] PAC Chemical Database, U.S. Department of Energy
Boiling point: 163.5 °C @760 [mmHg][5]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source
163.5 °C 326.3 °F at 760 mmHg (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
164 °C 164 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
163.5 °Cshown 163.5 °C @760 [mm Hg] [5] PAC Chemical Database, U.S. Department of Energy
Density: 0.959 @25 °C[5]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source
– 0.958 at 68 °F (USCG, 1999) - Less dense than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
– Relative density (water = 1): 0.96 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown 0.959 @25 °C [5] PAC Chemical Database, U.S. Department of Energy
Solubility in water: Solubility in water: miscible[3]
3 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– greater than or equal to 100 mg/mL at 66 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
– In water, 6.00X10+4 mg/L at 25 °C [4] Hazardous Substances Data Bank (HSDB)cites Hemphill L, Swanson WS; Proc of the 18th Industrial Waste Conf, Eng Bull Purdue U, Lafayette, IN 18:204-17 (1964)
–shown Solubility in water: miscible [3] ILO-WHO International Chemical Safety Cards (ICSCs)
log P: 0.79[3]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
– log Kow= 0.79 [4] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 9
–shown 0.79 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
pKa: pKa = 4.82 at 25 °C[4]
Vapor pressure: Vapor pressure, Pa at 20 °C: 57[3]
4 values
2 of 3 sources agree on it (most common value).
Value As written Source
0.43 mmHg 0.43 mmHg at 68 °F [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
1.4 mmHg 1.4 mmHg at 86 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
0.43 mmHgshown Vapor pressure, Pa at 20 °C: 57 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
1.65 mmHg 1.65 [mm Hg] @25 °C [5] PAC Chemical Database, U.S. Department of Energy
Flash point: 72 °C (161 °F) (Closed cup)[4]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
77 °C 170 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
72 °Cshown 161 °F (72 °C) (Closed cup) [4] Hazardous Substances Data Bank (HSDB)cites Fire Protection Guide to Hazardous Materials. 13 ed. Quincy, MA: National Fire Protection Association, 2002., p. 325-27
72 °C 72 °C c.c. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Autoignition temperature: 452 °C[3]
3 values
Sources disagree; from ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative.
Value As written Source
450 °C 842 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
443 °C 830 °F (443 °C) [4] Hazardous Substances Data Bank (HSDB)cites Fire Protection Guide to Hazardous Materials. 13 ed. Quincy, MA: National Fire Protection Association, 2002., p. 325-27
452 °Cshown 452 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
–	Butyric acid appears as a colorless liquid with a penetrating and unpleasant odor. Flash point 170 °F. Corrosive to metals and tissue. Density 8.0 lb /gal.	[1] CAMEO Chemicals
–	Liquid; CBI	[2] EPA Chemical Data Reporting (CDR)
–	COLOURLESS OILY LIQUID WITH CHARACTERISTIC ODOUR.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown	Colorless liquid	[4] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 14th Edition. John Wiley & Sons, Inc. New York, NY 2001., p. 183

Value	As written	Source
−7.9 °Cshown	17.8 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
−7.9 °C	-7.9 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−5.1 °C	-5.1 °C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
163.5 °C	326.3 °F at 760 mmHg (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
164 °C	164 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
163.5 °Cshown	163.5 °C @760 [mm Hg]	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–	0.958 at 68 °F (USCG, 1999) - Less dense than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–	Relative density (water = 1): 0.96	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown	0.959 @25 °C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–	greater than or equal to 100 mg/mL at 66 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
–	In water, 6.00X10+4 mg/L at 25 °C	[4] Hazardous Substances Data Bank (HSDB)cites Hemphill L, Swanson WS; Proc of the 18th Industrial Waste Conf, Eng Bull Purdue U, Lafayette, IN 18:204-17 (1964)
–shown	Solubility in water: miscible	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
–	log Kow= 0.79	[4] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 9
–shown	0.79	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
0.43 mmHg	0.43 mmHg at 68 °F	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
1.4 mmHg	1.4 mmHg at 86 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
0.43 mmHgshown	Vapor pressure, Pa at 20 °C: 57	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
1.65 mmHg	1.65 [mm Hg] @25 °C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
77 °C	170 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
72 °Cshown	161 °F (72 °C) (Closed cup)	[4] Hazardous Substances Data Bank (HSDB)cites Fire Protection Guide to Hazardous Materials. 13 ed. Quincy, MA: National Fire Protection Association, 2002., p. 325-27
72 °C	72 °C c.c.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
450 °C	842 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
443 °C	830 °F (443 °C)	[4] Hazardous Substances Data Bank (HSDB)cites Fire Protection Guide to Hazardous Materials. 13 ed. Quincy, MA: National Fire Protection Association, 2002., p. 325-27
452 °Cshown	452 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 6
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0.75
H-bond donors: 1
H-bond acceptors: 1 computed here · PubChem 2
Rotatable bonds: 2
TPSA (Å²): 37.3
Formal charge: 0
XLogP3: 0.8 PubChem
Complexity: 49 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C54.53%
H9.15%
O36.32%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 0.87 Crippen (Wildman and Crippen 1999)
log S (water solubility): -0.8 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 1.74 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 88.11
log P ≤ 5 (Crippen): 0.87
H-bond donors ≤ 5: 1
H-bond acceptors ≤ 10: 1

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [6].

Corrosive

NFPA 704[4]

H314Causes severe skin burns and eye damage

Precautionary statements: P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501

View all classifications (2)

[6] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH314
[7] European Chemicals Agency (ECHA) · 2,131 reports · DangerH302, H314, H318

First aid

Eyes: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. Immediately transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. Skin: Immediately flood affected skin with water while removing and isolating all contaminated clothing.[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]
Fresh air, rest. Artificial respiration may be needed. Refer for medical attention.[3]
Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention .[3]

Storage

Separated from strong oxidants, strong bases and food and feedstuffs.[3]
Store in cool, dry, well-ventilated location, away from any area where fire hazard may be acute.[4]
Outside or detached storage is preferred. Separate from oxidizing materials, heat, oxidizers, and sunlight.[4]

Incompatibilities

May attack aluminum or other light metals with formation of flammable hydrogen gas.[4]
(butyric acid) can react with oxidizing materials.[4]
A mixture of chromium trioxide and butyric acid became incandescent on heating to 100 °C. (chromium trioxide)[4]

Safety data sheets on the supplier’s page: Finetech Industry Limited, Enamine, MolCore.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[5]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[6]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[7]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[8]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[9]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
[10]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[11]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[12]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[13]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[14]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.

Similar structures

Tanimoto similarity on Morgan fingerprints (radius 2) with RDKit 2026.09, at least 45%.