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CHEMINFO Record Number: 414
CCOHS Chemical Name: Isovaleric acid

Delphinic acid
Isobutyl formic acid
Isopentanoic acid
Isopropylacetic acid
Isovalerianic acid
3-Methylbutanoic acid
3-Methylbutyric acid
beta-Methylbutyric acid
Valeric acid (non-specific name)
Pentanoic acid (non-specific name)
Acide isovalerique

CAS Registry Number: 503-74-2
RTECS Number(s): NY1400000
EU EINECS/ELINCS Number: 109-852-2
Chemical Family: Aliphatic carboxylic acid / saturated aliphatic monocarboxylic acid / alkanoic acid / pentanoic acid / valeric acid
Molecular Formula: C5-H10-O2
Structural Formula: CH3-CH(CH3)-CH2-C(=O)-OH


Appearance and Odour:
Dense, clear, colourless liquid with a disagreeable, rancid-cheese odour.(8,9,10)

Odour Threshold:
1.5 ppb (not specified); 17 to 24 ppb (0.07 to 0.1 mg/m3) (recognition); 0.72 ppm (3 mg/m3) (recognition) (8)

Warning Properties:
GOOD - detectable by odour at low concentrations which are unlikely to be harmful.

Isovaleric acid is one of four different chemical forms (isomers) of valeric acid. It is commercially available as a pure acid. This CHEMINFO record contains information specific to isovaleric acid supplemented by general information for all forms of valeric acid. For information on n-valeric acid or pivalic acid (another isomer), refer to CHEMINFO records 413 or 415, respectively.

Uses and Occurrences:
Fragrance ingredient in perfumes; flavour ingredient in non-alcoholic beverages and foods, such as ice cream, candy, baked goods and cheese; chemical intermediate for sedatives, narcotics and other drugs, fungicides and rodenticides; and the manufacture of esters (used as solvents and softeners and in perfumes).(1,11,12) Isovaleric acid occurs naturally in many plants, including tobacco, valerian, and the essential oils of cypress, citronella, geranium, and hops. It occurs naturally in the body.(1)


Dense, clear, colourless liquid with a disagreeable, rancid-cheese odour. COMBUSTIBLE LIQUID AND VAPOUR. Liquid may accumulate static charge. Causes skin and eye irritation.


Effects of Short-Term (Acute) Exposure

The mist or vapour can cause irritation of the nose, throat and lungs, based on limited animal evidence for n-valeric acid and physical properties. These effects may be mild to severe depending on the airborne concentration. Symptoms would include nasal irritation, sore throat, coughing, hoarseness and, in extreme exposures, difficulty breathing. There is no human information available.

Skin Contact:
Isovaleric acid may cause moderate to severe skin irritation depending upon the concentration of chemical and the duration of contact, based on limited animal information. Some other forms of valeric acid are corrosive. Prolonged exposures or concentrated solutions may cause burns and blistering. There is no human information available.
Based on animal evidence, isovaleric acid can probably be absorbed through the skin, but is not expected to cause toxic effects by this route of exposure.

Eye Contact:
Contact with vapour, mist or splashes of very dilute solutions can probably cause redness and pain. Direct contact with concentrated solutions can probably cause corneal burns, based on animal information for valeric acid, mixed isomers. Permanent injury, including blindness, may occur. There is no specific human or animal information available for isovaleric acid.

Isovaleric acid is used as a flavouring ingredient in non- alcoholic beverages and in foods such as ice cream, candy, baked goods and cheese.(1) Isovaleric acid is probably a corrosive liquid and concentrated solutions can cause severe irritation or corrosive injury to the mouth, throat and stomach. Permanent injury and death could result.
There is no specific human or animal information available. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

SKIN CONTACT: Repeated or prolonged skin contact may cause redness, dryness and itching of the skin (dermatitis).

SKIN SENSITIZATION: No sensitization reactions were observed following application of 1% isovaleric acid to the skin of 31 volunteers (maximization test).(2,unconfirmed)


There is no human or animal information available.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human or animal information available for isovaleric acid. n-Valeric acid did not cause developmental effects in one animal study.

Reproductive Toxicity:
There is no human or animal information available.

There is no information available.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Isovaleric acid does not accumulate in the body. It is readily absorbed from the gastrointestinal tract in humans and is rapidly broken down to two- and three-carbon fragments, which are in turn readily metabolized and used in the production of chemicals required for bodily function (the isopropyl fragment), or excreted. Isovaleric acid occurs naturally in the body and is an intermediate in the metabolism of the amino acid leucine.(1)


If symptoms develop, remove source of contamination or move victim to fresh air. If irritation persists, obtain medical advice immediately.

Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective gloves, if necessary. As quickly as possible, flush with lukewarm, gently flowing water for at least 20 minutes, or until the chemical is removed. Under running water, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). If irritation persi sts, repeat flushing. Obtain medical attention immediately. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, or until the chemical is removed, while holding the eyelid(s) open. Take care not to rinse contaminated water into the non-affected eye or onto the face. If irritation persists, repeat flushing. Obtain medical attention immediately.

NEVER give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, have victim rinse mouth and repeat administration of water. Obtain medical attention immediately.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
70 deg C (158 deg F) (closed cup) (13)

Lower Flammable (Explosive) Limit (LFL/LEL):
1.5% (13)

Upper Flammable (Explosive) Limit (UFL/UEL):
Not available

Autoignition (Ignition) Temperature:
416 deg C (781 deg F) (14); 440 deg C (824 deg F) (12,13)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Isovaleric acid can accumulate static charge by flow or agitation due its very low electrical conductivity (less than 40 pS/m).(15)

Combustion and Thermal Decomposition Products:
Incomplete combustion may produce irritating fumes and acrid smoke.

Fire Hazard Summary:
Combustible liquid. Can form explosive mixtures with air at, or above, 70 deg C. During a fire irritating/toxic gases may be formed. Closed containers may rupture violently when exposed to fire or excessive heat for sufficient time.

Extinguishing Media:
Dry chemical powder, carbon dioxide, alcohol foam, polymer foam, water spray or fog.(13)

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or protected location. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
If possible, isolate materials not yet involved in the fire, and move containers from fire area if this can be done without risk, and protect personnel. Otherwise, fire-exposed containers or tanks should be cooled by application of hose streams. Application should begin as soon as possible and should concentrate on any unwetted portions of the container. If this is not possible, use unmanned monitor nozzles and immediately evacuate the area.
If a leak or spill has not ignited, use water spray in large quantities to disperse the vapours, protect personnel attempting to stop a leak and to dilute the spill to a nonflammable mixture. Water spray may be used to flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
For a massive fire in a large area, use unmanned hose holder or monitor nozzles. If this is not possible, withdraw from fire area and allow fire to burn. Stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank due to fire.

Protection of Fire Fighters:
Isovaleric acid and its decomposition products may be hazardous to health. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical protective clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) may be necessary.


NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury.
NFPA - Flammability: 2 - Must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.


Molecular Weight: 102.13

Conversion Factor:
1 ppm = 4.17 mg/m3; 1 mg/m3 = 0.240 ppm at 20 deg C (calculated)

Physical State: Liquid
Melting Point: -29 deg C (-20.2 deg F) (1,13); - 37 deg C (-34.6 deg F) (5,9,10,12)
Boiling Point: 176-177 deg C (348.8-350.6 deg F) (5,9,12)
Relative Density (Specific Gravity): 0.925-0.929 at 20 deg C (water = 1) (13,17)
Solubility in Water: Moderately soluble (4.2 g/100 mL) at 20 deg C (1,9)
Solubility in Other Liquids: Soluble in all proportions in ethanol, chloroform and diethyl ether (1)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 0.93-1.51 (calculated) (18)
pH Value: 2.89 (0.1 M solution in water) (calculated)
Vapour Density: 3.52 (air = 1)
Vapour Pressure: 0.049 kPa (0.37 mm Hg) at 20 deg C (13); 0.133 kPa (1 mm Hg) at 34 deg C (9)
Saturation Vapour Concentration: 487 ppm (0.05%) at 20 deg C; 1300 ppm (0.132%) at 34 deg C (calculated)
Evaporation Rate: Not available
Critical Temperature: 416 deg C (781 deg F)

Other Physical Properties:
ACIDITY: Weak acid; pKa = 4.77 at 25 deg C (Ka = 1.7 x 10(- 5)) (17)
VISCOSITY-DYNAMIC: 2.45 mPa.s (2.45 centipoises) (12)
VISCOSITY-KINEMATIC: Approximately 2.61 to 2.64 (calculated)


Normally stable

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

OXIDIZING AGENTS (e.g. chromium trioxide, nitric acid, peroxides, permanganates) - may react violently or explosively. Increased risk of fire.(13)
BASES (including alkalis, such as sodium hydroxide) - vigorous or violent reaction may occur, yielding heat and pressure.(13)
REACTIVE METALS (e.g. powdered aluminum, zinc) - may produce flammable hydrogen gas.
REDUCING AGENTS (e.g. hydrides such as lithium aluminum hydride) - reaction may be vigorous or violent.(13)
PHOSPHORUS TRICHLORIDE - may form spontaneously flammable phosphine and explode.(19)
POTASSIUM t-BUTOXIDE (solid) - may ignite.(19)

Hazardous Decomposition Products:
None reported

Conditions to Avoid:
Temperatures above 70 deg C, open flames

Corrosivity to Metals:
Corrosive to grey cast iron, steel and lead. Not corrosive to aluminum, type 304 and 316 stainless steels, nickel cast iron, copper and its alloys, bronze, brass and copper-nickel, and nickel-chromium-iron-molybdenum and nickel-chromium-molybdenum alloys.(20,21)


LD50 (oral, rat): 1060 mg/kg (mixed isomers) (3); 1900 mg/kg (mixed isomers) (4); 2000 mg/kg (isovaleric acid) (5, unconfirmed)

LD50 (dermal, rabbit): 3560 mg/kg (isovaleric acid) (6)

Eye Irritation:

Isovaleric acid is a severe eye irritant.

Application of an excess of a 15% solution of valeric acid (mixed isomers) caused severe injury in rabbits (graded 8/10; scored over 5 where 5 is severe injury).(3) In another test, application of in excess of a 5% solution of valeric acid (mixed isomers) caused severe injury in rabbits (graded 9/10; scored over 5 where 5 is severe injury).(4)

Skin Irritation:

Application of 0.01 mL of undiluted valeric acid (mixed isomers) produced tissue death (necrosis) (graded 6/10) in rabbits in two separate tests.(3,4) No visible tissue destruction was observed in rabbits following application of 0.5 mL of isovaleric acid for 4 hours in a test which prevented evaporation from the skin. However, the degree of irritation was not described.(6)

Effects of Long-Term (Chronic) Exposure:

No harmful effects were observed in rats fed up to 5% isovaleric acid for 90 days.(7) These findings with a high dietary level indicate this acid has a low oral toxicity.


Selected Bibliography:
(1) Katz, G.V., et al. Aliphatic carboxylic acids. In: Patty's industrial hygiene and toxicology. 4th edition. Edited by G.D. Clayton et al. Volume II. Toxicology. Part E. John Wiley and Sons, 1994 . p. 3523-3527, 3529, 3544-3546
(2) Opdyke, D.L.J. Monographs on fragrance raw materials: isovaleric acid. Food and Cosmetics Toxicology. Special issue V. Vol. 17, supplement (December, 1979). p. 841-843
(3) Smyth, H.F., Jr., et al. Range-finding toxicity data: list VI. Industrial Hygiene Journal. (1962). p. 99
(4) Smyth, H.F., Jr., et al. Range-finding toxicity data : list VII. American Industrial Hygiene Association Journal. Vol. 30, no. 5 (September-October, 1969). p. 472
(5) Bagby, M.O. Carboxylic acids: survey. In: Kirk-Othmer encyclopedia of chemical technology. 4th edition. Volume 5. John Wiley and Sons, 1993. p. 147-168
(6) Vernot, E.H., et al. Acute toxicity and skin corrosion data for some organic and inorganic compounds and aqueous solutions. Toxicology and Applied Pharmacology. Vol. 42 (1977). p. 417-423
(7) Amoore, J.E., et al. Synthetic flavors: efficiency and safety factors for sweaty and fishy odorants. Chemical Senses and Flavour. Vol. 3, no. 3 (1978). p. 307-317
(8) Verschueren, K. Handbook of environmental data on organic chemicals. 2nd edition. Van Nostrand Reinhold, 1983. p. 47, 783- 784
(9) Verschueren, K. Handbook of environmental data on organic chemicals. 3rd edition. Van Nostrand Reinhold, 1996. p. 1178- 1179
(10) Budavari, S, ed. The Merck index: an encyclopedia of chemicals, drugs, and biologicals. 12th edition. Merck and Co., Inc., 1996. p. 893
(11) HSDB record for isovaleric acid. Last revision date: 96/01/19
(12) Riemenschneider, W. Carboxylic acid, aliphatic. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised edition. Volume A 5. VCH Verlagsgesellschaft, 1985. p. 235-246
(13) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 2048A
(14) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325
(15) Lange's handbook of chemistry. 12th edition. Edited by J.H. Dean. McGraw-Hill Book Company, 1979. p. 6-36 to 6-37
(16) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 3rd edition. Van Nostrand Reinhold, 1997
(17) Weast, R.C., ed. Handbook of chemistry and physics. 66th edition. CRC Press, 1985-1986. p. C-331, D-162, D-200
(18) Leo, A., et al. Partition coefficients and their uses. Chemical Reviews. Vol. 71, no. 6 (December, 1971). p. 567
(19) Urben, P.G., ed. Bretherick's handbook of reactive chemical hazards. 5th edition. Volume 1. Butterworth-Heinemann Ltd., 1995. p. 567, 1350
(20) Corrosion data survey: metals section. 6th edition. National Association of Corrosion Engineers, 1985. p. 74-8 to 75-8
(21) Elder, G.B. Corrosion by organic acid. In: Process industries corrosion. National Association of Corrosion Engineers, 1975. p. 247-254

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1997-05-28

Revision Indicators:
Resistance of materials 1998-04-01
Bibliography 1998-04-01
Emergency overview 2000-08-01
Acute exposure (ingestion) 2000-08-01
First aid (ingestion) 2000-08-01
Emergency overview 2000-08-01
Acute exposure (ingestion) 2000-08-01
First aid (ingestion) 2000-08-01
Bibliography 2003-03-25
NFPA (health) 2003-03-25
NFPA (flammability) 2003-03-25

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