PROPANE - (74-98-6)


Name: propane; n-propane
CAS Number: 74-98-6
Chemical Formula: C3H8 or CH2CH3CH2
Molar Mass: 44.09562 g
State of Matter: colorless gas
Mass Percent: C 81.713 %; H 18.286 % 


• organic • alkane


• "As fuel gas, sometimes mixed with butane. In organic syntheses. As refrigerant." 1

• "About 100 billion liters (27 billion gallons) of propane were produced in the United States in 2004. The largest portion of that output (45 percent) was used for space heating, water heating, the operation of appliances, and other purposes in commercial and residential buildings. Propane has many advantages as a fuel:
• It produces less pollution that gasoline or coal.
• Propane water heaters are less expensive to purchase and operate than are electric water heaters, and thet can heat more water than electric water heaters.
• Propane fireplaces are less expensive and less polluting than wood-burning fireplaces, and they can be turned on and off with a switch.
• Many professional cooks prefer propane stoves to electric stoves because they heat instantly and are easier to control.
• Propane dryers take three-quarters of the time of electric dryers to dry the same amount of clothes.
• Propane appliances continue to operate during power outages, unlikes electric appliances.
The second most important application of propane is in the petrochemical industry where the compound is used for the production of a host of organic chemicals, primarily ethylene and propylene. Ethylene and propylene are two important compounds used in the production of plastics and other kinds of polymers. They ranked third and sixth on the list of the largest volume chemicals produced in the United States in 2004.
Farm use and industrial use follow next in importance, each accounting for about 7 percent of the propane used in the United States each year. On farms, propane is used to operate farm equipment and irrigation systems, to dry crops, and to help control weeds. In industries, the compound is used for space heating, for soldering, for cutting and treating metals, and as a fuel for fork lifts. Finally, a relatively small amount of propane is used as a fuel for cars, trucks, and other vehicles. Many people argue that more vehicles should be built to operate on propane because the gas produces fewer pollutants, reduces wear and tear on engines, and burns more efficiently than gasoline. So far, however, propane-powered vehicles have not become very popular in the United States. In the early 2000s, there were about 350,000 propane-powered vehicles in the United States and about 4 million in the world.
In moderate amounts, propane presents no health hazards to humans. In larger quantities, it may have a narcotic effect, producing drowsiness, disorientation, headaches, and confusion. The gas is both flammable and explosive and requires special care when being used." 2

Physical Properties

Melting Point:*
-187.6°C 3 = 85.55 K = -305.68°F
Boiling Point:*
-44.5°C 4 = 228.65 K = -48.1°F
-42.1°C 3 = 231.05 K = -43.78°F
Density (g/cm3):
0.493 at 25°C 3
* - 1 atm pressure


slightly soluble:  4
soluble:  • • 4


Double Bonds: 0
Triple Bonds: 0
Sigma Bonds: 10
Pi Bonds: 0
Total: 10
Carboxyl Groups: 0
Hydroxyl Groups: 0
Hybridization: all carbons are sp3
Bonding: polar covalent
Ionic Character: 10.61 %


ΔHf° (g): -24.82 kcal/mol 5 = -103.85 kJ/mol
S° (g): 64.58 cal/(mol•K) 6 = 270.20 J/(mol•K)
ΔGf° (g): -5.63 kcal/mol 7 = -23.56 kJ/mol
The heat of combustion is the amount of heat released when one mole of a substance undergoes combustion according to the general reaction equation:
CxHyOz + 0.25(4x+y-2z) O2 (g) → x CO2 (g) + 0.5y H2O (ℓ)

ΔHcomb° (g): -530.59 kcal = -2220.00312 kJ

Safety Information

NFPA 704 Ratings:
Health: 1 - Exposure would cause irritation with only minor residual injury.
Flammability: 4 - Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Includes pyrophoric substances. Flash point below 23°C (73°F).
Reactivity: 0 - Normally stable, even under fire exposure conditions, and is not reactive with water.

For More Information


(1) - The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 13th ed.; Budavari, S.; O'Neil, M.J.; Smith, A.; Heckelman, P. E.; Kinneary, J. F., Eds.; Merck & Co.: Whitehouse Station, NJ, 2001; entry 7891.
(2) - Schlager, Neil, Weisblatt, Jayne, Newton, David E., and Montney, Charles B. Chemical Compounds Vol. 3; Thomson-Gale: Detroit, MI, 2006; pp 665-6.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 3-269.
(4) - Estok, George K. Organic Chemistry: A Short Text; W.B. Saunders: Philadelphia, 1959; p 29.
(5) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:88.
(6) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:88.
(7) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:88.