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CHEMINFO Record Number: 106
CCOHS Chemical Name: Isobutyric anhydride

Isobutyric acid anhydride
Isobutyryl anhydride
Isobutyryl oxide
2-Methylpropanoic anhydride
2-Methylpropanoic acid anhydride
Anhydride isobutyrique

CAS Registry Number: 97-72-3
EU EINECS/ELINCS Number: 202-603-6
Chemical Family: Saturated aliphatic carboxylic acid anhydride / saturated aliphatic monocarboxylic acid anhydride / alkanoic acid anhydride
Molecular Formula: C8-H14-O3
Structural Formula: CH3-CH(CH3)-C(=O)-O-C(=O)-CH(CH3)-CH3


Appearance and Odour:
Colourless liquid (1,2)

Odour Threshold:
Not available

Warning Properties:
Information not available for evaluation.

Uses and Occurrences:
Used as a chemical intermediate; for the esterification of cellulose and sucrose; in the manufacture of odourants, peroxide catalysts, flavours and perfumes; and as a flavour and/or aroma enhancer.(1,3,4)


Colourless liquid. COMBUSTIBLE LIQUID AND VAPOUR. Vapour is probably irritating to the respiratory tract. May be corrosive to the eyes and skin. May cause permanent eye damage, including blindness, or permanent scarring of the skin.


Effects of Short-Term (Acute) Exposure

Isobutyric anhydride reacts with moisture in the nose, throat and lungs to form corrosive isobutyric acid. Therefore, inhalation of vapours or mists can probably result in mild to severe irritation of the nose, throat and lungs. Symptoms would include nose irritation, sore throat, coughing, hoarseness and, in extreme exposures, difficulty breathing. There is no human or animal information available for isobutyric anhydride.

Skin Contact:
Isobutyric anhydride reacts with moisture on the skin to form corrosive isobutyric acid. Therefore, isobutyric anhydride can likely cause moderate to severe skin irritation depending upon the concentration of chemical and the duration of contact. Prolonged exposures to concentrated solutions may cause burns, blistering, and tissue destruction (corrosive effects).
It is not known if isobutyric anhydride can be absorbed through the skin, however irritation/corrosion is the main effect.

Eye Contact:
Isobutyric anhydride reacts with moisture in the eye to form corrosive isobutyric acid. Contact with vapour, mist or splashes of dilute solutions of isobutyric acid can probably cause redness and pain. Contact with concentrated solutions can probably cause corneal burns. Permanent eye damage, including blindness, may occur. There is no human or animal information available for isobutyric anhydride.

Isobutyric anhydride reacts with moisture in the throat and stomach to form corrosive isobutyric acid. Isobutyric acid is corrosive and ingestion of concentrated solutions of isobutyric anhydride may cause severe irritation or corrosive injury to the mouth, throat and stomach.
There is no human or animal information available for isobutyric anhydride. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

There is no human or animal information available.


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.

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:
Isobutyric anhydride does not accumulate in the body. It is slowly converted to isobutyric acid by water or body fluids. Isobutyric acid does not accumulate in the body. It is metabolized to propionic acid, which is ultimately converted to glucose and glycogen (used by the body), and to carbon dioxide, which is exhaled.


Remove source of contamination or have victim to fresh air. If symptoms persist, obtain medical attention immediately.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. Quickly and gently blot away excess chemical. Remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Flush contaminated area with large volumes of lukewarm, gently flowing water for 20-30 minutes, by the clock. If irritation persists, repeat flushing. Obtain medical attention immediately. Completely decontaminate clothing, shoes or leather goods before re-use or discard.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Quickly and gently blot away excess chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20-30 minutes, by the clock, while holding the eyelid(s) open. If irritation persists, repeat flushing. Take care not to rinse contaminated water into the unaffected eye or onto the face. Obtain medical attention immediately.

NEVER give anything by mouth if the victim is rapidly losing consciousness, is unconscious or is 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 to dilute material in the stomach. If milk is available, it may be administered AFTER the water has been given. 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:
59 deg C (139 deg F) (closed cup) (5)

Lower Flammable (Explosive) Limit (LFL/LEL):
1.0% (5)

Upper Flammable (Explosive) Limit (UFL/UEL):
6.2% (5)

Autoignition (Ignition) Temperature:
329 deg C (625 deg F) (5)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material

Sensitivity to Static Charge:
No information is available.

Combustion and Thermal Decomposition Products:
Corrosive isobutyric acid, acrid smoke and other toxic, irritating fumes of unburned anhydride and products of incomplete combustion.(2)

Fire Hazard Summary:
Combustible liquid. Can form explosive mixtures with air, at or above, 59 deg C. During a fire irritating/toxic gases may be formed. Vapours from warmed liquid can accumulate in confined spaces, resulting in a explosion and toxicity hazard. Water reacts slowly with isobutyric anhydride at normal temperatures, but more rapidly and violently under fire conditions, to form corrosive isobutyric acid and give off heat. The reaction is hazardous in a confined space, since an explosion can result. Closed containers may rupture violently when exposed to fire or excessive heat for sufficient time.

Extinguishing Media:
Dry chemical powder, carbon dioxide, alcohol foam and polymer foam.(2) Water is an effective extinguishing agent, but must be used in flooding quantities to completely solubilize the anhydride and fully absorb the heat of reaction.

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.
Closed containers may rupture violently when exposed to heat of fire. 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. DO NOT get water into isobutyric anhydride containers. If it is not possible to cool the containers, 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, but be aware that flying material from ruptured tanks may travel in any direction. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank due to fire.
Isobutyric anhydride is slightly hazardous to health, but forms hazardous decomposition products. 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 resistant clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/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: 1 - Normally stable, but can become unstable at elevated temperatures and pressures, or may react vigorously, but non-violently with water.


Molecular Weight: 158.20

Conversion Factor:
1 ppm = 6.46 mg/m3; 1 mg/m3 = 0.16 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: -53.5 deg C (-64 deg F) (3,6); -56 deg C (-69 deg F) (2,7)
Boiling Point: 182 deg C (360 deg F) (2,7)
Relative Density (Specific Gravity): 0.954 at 20 deg C (water = 1) (2,6,7)
Solubility in Water: Decomposes to form isobutyric acid (2,3)
Solubility in Other Liquids: Soluble in diethyl ether and chloroform.(3,6)
Coefficient of Oil/Water Distribution (Partition Coefficient): Not applicable (reacts)
pH Value: Not applicable. Reacts with water to form acidic solutions.
Vapour Density: 5.5 (air = 1) (5)
Vapour Pressure: 0.067 kPa (0.50 mm Hg) at 20 deg C (3)
Saturation Vapour Concentration: 660 ppm (0.066%) at 20 deg C (calculated)
Evaporation Rate: Not available
Critical Temperature: Not available


Decomposes in the presence of moist air or water to form isobutyric acid.(2,3)

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.

STRONG OXIDIZING MATERIALS (e.g. chromic trioxide, hypochlorous acid, nitric acid, peroxides, potassium permanganate) - can react rapidly and violently with a risk of fire and/or explosion.(2)
STRONG ALKALIS or CAUSTICS (e.g. sodium or potassium hydroxide) or BASES (e.g. 2-aminoethanol or ethylene diamine) - may react violently with spattering, accompanied by a temperature and pressure rise.(2)
WATER - reacts to form corrosive isobutyric acid and heat.(2,3)

Hazardous Decomposition Products:
Corrosive isobutyric acid.

Conditions to Avoid:
Temperatures above 59 deg C and moisture.

Corrosivity to Metals:
No specific information is available. The related butyric anhydride (pure and moisture-free) is not corrosive to cast iron, steel, stainless steels, copper, bronze, nickel and its alloys, aluminum, tantalum, titanium, lead and silver.(8) In the presence of moisture, isobutyric anhydride forms isobutyric acid and may be corrosive to steel, cast iron, and lead. Aluminum may be attacked at elevated temperatures.


There is no animal information available.


Selected Bibliography:
(1) HSDB record for 2-methylpropanoic anhydride. Last revision date: 97/04/23
(2) The Sigma-Aldrich library of chemical safety data. Ed. II. Vol. 1. Sigma-Aldrich Corporation, 1988
(3) Center for Chemical Hazard Assessment, Syracuse Research Corporation. Isobutyric anhydride. In: Information profiles on potential occupational hazards: organic anhydrides. SRC TR 81-635. Second draft. National Institute for Occupational Safety and Health, Feb. 1982. p. 48-50
(4) Hawley's Condensed Chemical Dictionary. Revised by R.J. Lewis, Sr. 12th ed. Van Nostrand Reinhold Company Inc., 1993
(5) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325
(6) Weast, R.C., ed. Handbook of chemistry and physics. 66th ed. CRC Press, 1985-1986
(7) Dean, J.A. Lange's handbook of chemistry. 14th ed. McGraw-Hill, Inc., 1992
(8) Corrosion data survey: metals section. 6th ed. National Association of Corrosion Engineers, 1985. p. 26-5 to 27-5

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: 1998-06-22

Revision Indicators:
Emergency overview 2000-08-01
Acute exposure (ingestion) 2000-08-01
First aid (ingestion) 2000-08-01
RTECS No 2002-02-27
TDG 2002-06-11
Bibliography 2003-04-18
NFPA (health) 2003-04-18
NFPA (specific hazards) 2003-04-19

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