CHEMICAL DATA NOTEBOOK SERIES #82: CYCLOPENTANE
HAZARDOUS MATERIALS
Cyclopentane is a flammable, moderately toxic, slightly irritating, narcotic, clear, colorless liquid with an odor reminiscent of gasoline. It is used as a component of gasoline, as a solvent, and as a raw material in the manufacture of other chemicals.
PROPERTIES
Cyclopentane has a flash point of
— 35°F, an ignition temperature of 682°F, a flammable range of from 1.1 to 8.7 percent in air, a specific gravity of 0.745, a molecular weight of 70, a vapor density of 2.42, a boiling point of 120.6°F, and a freezing point of — 135.9°F. It is not soluble in water.
Cyclopentane has only one synonym, pentamethylene. Its molecular formula is C5H10, which is the same as that of 1-pentene (or pentylene), making cyclopentane an isomer of pentene. An isomer is a compound that has the same molecular formula as another compound, but it differs in structural formula and in chemical and physical properties. 1-pentene is an alkene, which is an unsaturated hydrocarbon compound that contains only one double covalent bond. The table (at right) shows the differences among cyclopentane, 1-pentene, and pentane.
HAZARDS
Flammability is cyclopentane’s major hazard. Its flash point of – 35°F means that at almost any ambient temperature in our environment, any exposure or release of the liquid will provide enough vapors to form an ignitable mixture with the air near the surface of the liquid or the container. Its relatively low ignition temperature of 682°F means that only a small part of cyclopentane’s vapors must absorb enough energy to reach this temperature for ignition to occur. This ignition temperature is easily reached by all common ignition sources. Its lower flammable limit of 1.1 percent in air is reached easily, since cyclopentane is very volatile.
In any release of cyclopentane, all that is needed to cause an explosion is an ignition source, since it is almost guaranteed that sufficient vapors will be present to put the fuel into the flammable range.
Its vapor density of 2.42 ensures that cyclopentane vapors will sink to the ground and, unless disturbed by the wind or other movement, will flow downgrade until they locate an ignition source. At this point, the vapors will ignite explosively and flash back to the vapor source.
Although cyclopentane is considered only moderately toxic, severe problems can occur with overexposure. Any time high concentrations of cyclopentane vapors are present, they may pose a serious inhalation hazard. Concentrations of cyclopentane within the flammable limits could cause inhalation and respiratory problems. Unprotected persons can be subjected to symptoms that include breathing difficulties, disorientation, dizziness, drowsiness, nausea, vomiting, and even unconsciousness, coma, and death. Cyclopentane can cause narcosis and depress the central nervous system.
If liquid cyclopentane contacts the eyes, it will irritate them, causing redness and tearing. Inflammation of the iris is also a possibility.
Contact of liquid cyclopentane with the skin causes defatting by solvent action. Prolonged or repeated contact causes cracking of the skin, creating the possibility of infection.
Ingesting cyclopentane can produce very serious consequences, including death. Among the effects of ingesting cyclopentane could be severe irritation of the gastrointestinal tract; many of the problems caused by inhalation; and damage to the brain, heart, liver, and lungs. Aspirating cyclopentane into the lungs can cause chemical pneumonitis and/or pulmonary edema, which sometimes occurs on a delayed basis.
The ACGIH (American Conference of Governmental Industrial Hygienists) TLV-TWA (threshold limit valuetime weighted average) and OSHA’s (Occupational Safety and Health Administration) PEL (permissible exposure limit) for cyclopentane are the same, 600 ppm (parts per million of air). The ACGlH’s STEL (short-term exposure limit) is 900 ppm.
Cyclopentane is considered a stable chemical and is not particularly reactive with many chemicals. Since it is a hydrocarbon fuel, however, it may ignite or otherwise react if it comes in contact with strong oxidizing agents.
A cyclical compound, cyclopentane has a closed structure with no ends; the carbon atoms are bound to each other in a more or less pentagonal shape. As a saturated hydrocarbon, it has no multiple (double or triple) covalent bonds. Its name is derived from its structural characteristics: cyclo, since it is a cyclical compound, and pentane, since it is a saturated hydrocarbon with five carbon atoms, making it the fifth compound in the alkane series. The analogous series of cycloalkanes starts with cyclopropane (three carbons), then cyclobutane (four carbons), cyclopentane, cyclohexane (six carbons), cycloheptane (seven carbons), and perhaps cyclooctane (eight carbons). The “perhaps” means that since the molecules of cyclical compounds containing more than six carbon atoms begin to become unwieldy and, therefore, unstable, they may not exist for very long but will break down into other compounds.
NONFIRE RELEASE
Because of the danger of explosion, consider evacuating an area within one-half to one mile of an emergency involving cyclopentane. The exposed area downwind is most seriously threatened because of the tendency of cyclopentane vapors to hang together for great distances. The vapors tend to concentrate in low areas or confined spaces. Anyone without respiratory protection wandering into such an area may not be threatened as much by the vapors’ toxicity as by the exclusion of oxygen. The evacuation radius is determined by the size of the container, the form of the product being released (vapor or liquid) from the container, or the size of the liquid spill.
As is the case with an accidental release of all flammable liquids, approach the area from upwind, eliminate all ignition sources, and position equipment with the possibility of a wind shift in mind.
If vapors are escaping from the container, you could attempt to plug the opening if it can be done without creating sparks or friction heat sufficient to ignite the vapors. Any vapors released will not be cold or under high pressure; therefore, they quickly will sink to the ground. Consider dispersing the vapors with a highpressure water fog to prevent an accumulation of vapors within the flammable range from moving downwind.
After evacuation, containing the liquid release must be the next consideration. You can create containment ponds by pushing up dirt or another absorbent material around the spill. If equipment is available, containment pits may be dug. Use nonsparking tools and equipment in any mitigation technique involving flammable liquids.
In some cases, the liquid may be leaking from its container in a way that it can be captured and recycled back into the tank. It might be possible to catch the liquid in another secure container and remove it from the scene or to collect it in a temporary container and pump it back into the leaking container. This technique is not a totally satisfactory one, since cyclopentane is so volatile that large amounts of vapor are liberated as the liquid contacts the atmosphere. Pumps or other collection devices must be sparkproof.
If the leaking liquid is collected in a containment pond or pit, cover the surface of the liquid to slow down vapor evolution. Firefighting foam applied to the surface of the liquid may slow down the evaporation, but the foam layer may break down quickly and may have to be reapplied several times, adding to the volume of liquid in the pit or pond.
Vapors that evolve from the spill may be broken up by using highpressure fogs. A brisk breeze or wind will disperse the vapors, which tend to stay together. Any use of water to disperse the vapors necessitates having a containment dike to catch the runoff water.
Once the cyclopentane has been contained, the seller, buyer, or shipper of the product may try to salvage it by suctioning it from the containment pond or pit into secure containers. Any residual cyclopentane may be absorbed by adding clay, fly ash, peat moss, perlite, sand, sawdust, soil, straw, vermiculite, or other commercial sorbents. The sorbents used will be contaminated and have many of the hazards of the original material. They must be handled and disposed of in accordance with all federal, state, and local regulations.
Keep the cyclopentane from entering a sewer system or waterway. Should the liquid enter a sewer, it will vaporize quickly and fill the sewer line, upstream (some short distance) and downstream from where it enters, producing a serious explosion hazard at every catch basin and manhole opening downstream (and a few upstream) from the original entry point. Alert all sewage-treatment facilities immediately that cyclopentane has entered the system.
If the cyclopentane enters a river or stream, the liquid will float on the water’s surface. Very little of it will dissolve, since cyclopentane is practically insoluble in water. Notify all downstream users of the water at once, even though the product is practically nonsoluble.
Cyclopentane can be removed from moving water with oil spill containment booms. The booms will prevent materials floating on the water from passing and allow the water beneath the contamination to pass. The contained product then may be absorbed by a material such as straw or peat moss.
Another technique is to use a diversion dam to divert the stream or river into a low-lying area. Once all the contaminant is floating on the diverted water, the stream or river may be allowed to flow freely again. Environmental authorities must test the water downstream and determine that it is safe to use before downstream users can resume normal operations or drink the water.
Another technique is to use a bypass dam, with pipes well below the surface of the water, which will allow uncontaminated water to pass downstream while holding back the floating contaminant so that it can be salvaged, absorbed, or diverted.
Be cautious when steep-banked rivers and streams are involved, since evaporated vapors tend to stay near the surface of the water and flow downstream with it, producing potentially explosive atmospheres anywhere near the waterway.
If the product enters a pond, lake, or other standing body of water, oil spill containment booms can be used to contain the cyclopentane while efforts to salvage or absorb it are carried out. In all mitigation techniques, use sparkproof tools and equipment.
FIRE SCENARIO
Most emergency responders are concerned with the possibility of fire whenever flammable liquids are released, and they should be. However, when an ignition source is present near a release of a flammable liquid, especially an ignition source located some distance from the release, fire is the second concern. An explosion is the first consideration, as the vapors subsequently will contact that ignition source. The severity of the explosion depends on how far away the ignition source is and how much vapor has been generated. This kind of explosion usually is devastating and often kills and injures emergency responders and destroys firefighting equipment. The warnings about approaching from upwind and eliminating all possible ignition sources arcgiven to prevent such an explosive ignition of vapors. Of course, the goal also is to prevent a fire, but the possibility of an explosion often is overlooked.
When a fire is approaching a container of cyclopentane, the container must be kept cool by applying water with unmanned appliances from as far away as possible. Never approach a container threatened by flames or the radiated heat of a fire, and never get between a fire and containers of flammable or combustible liquids (or containers of compressed gas, for that matter). The possibility that the container will catastrophically fail and produce a fireball and spew flaming liquid is real; such a container failure will be fatal to all firefighters and anyone else nearby.
As an aside, the terms “flaming liquid” and “flammable liquid” arcmisnomers. Liquids do not and cannot burn. When a liquid is classified as flammable (its flash point is below 100°F) or combustible (flash point of 1()0°F or higher), it really means that the liquid’s vapors will burn. The liquid, therefore, cannot ignite unless it is in the vapor state, is within the flammable range, and meets an ignition source that will raise a very tiny amount of its vapor to the ignition temperature. When this occurs, an explosion is produced, and the heat from the explosion evaporates more liquid, ignites the newly generated vapors, and sustains the fire.
When heated by flames or radiated heat, the temperature of the cyclopentane (or any other contents of the container) rises and more vapors are produced. The pressure inside the container rises until the safety relief valve is activated. Usually a springloaded valve, the safety relief valve operates when the internal pressure of the container rises above the strength of the spring (usually onefourth of the container’s design strength). It then moves away from the container opening and allows vapors to escape until the container’s internal pressure drops below the strength of the spring, which then pulls the valve back into its seat, resealing the container.
The escaping vapors are almost always ignited on release. It is important that these vapors be allowed to continue to burn (unless the flame from the escaping vapors will cause some worse hazard), since burning vapors will prevent the accumulation of unburned vapors, which will explode violently when ignited. The only time flames from a leaking or venting container should be extinguished is if the flow of fuel can be stopped immediately after extinguishment.
burning cyclopentane may be extinguished with high-pressure water spray or fog, carbon dioxide, dry chemical, foam, or halon. Due to its low ignition temperature, extinguished fires of cyclopentane may reignite if the vapors contact a piece of heated metal or some other object above 682°F. The reignition may be explosive, especially if it is delayed and vapors have built up.
When large quantities of cyclopentane are burning, no human life or property is threatened, and no damage to the environment will occur, the safest technique may be to allow the fire to burn itself out.
PROTECTIVE CLOTHING AND EQUIPMENT
Choose protective clothing and equipment—including boots, face shields, gloves, and splashproof safety goggles—that prevent cyclopentane contact with the eyes and skin and vapor contact with the respiratory system. Protective materials may include nitrile rubber, polyvinyl alcohol, and Viton™. Another reference adds chlorinated polyethylene and Teflon™ to the list. Test all existing protective equipment and clothing for compatibility with cyclopentane before being exposed to it in an emergency situation.
FIRST AID
Inhalation. Move the victim to fresh air; keep him/her calm and warm. If the victim’s breathing has stopped or becomes labored, administer artificial respiration, being aware that such action might expose the first-aid giver to the material in the victim’s lungs and/or vomit. Seek immediate medical attention.
Eye contact. Flush the eyes immediately for at least 15 minutes, lifting the eyelids occasionally. Immediate medical attention is required.
Skin contact. Wash affected body areas with large amounts of soap and water. If irritation continues after washing, medical attention is needed.
Ingestion. Do not induce vomiting, and never try to make an unconscious person drink anything. Get immediate medical help
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
287-92-3
STCC
(Standard Transportation Commodity Code)
4908135
RTECS
(Registry of Toxic Effects of Chemical Substances) GY2390000
UN/NA
(United Nations/North America)
1146
CHRIS
(Chemical Hazard Response Information System) CAP
DOT
(U.S. Department of Transportation)
3.1, flammable liquid
NFPA 704 Rating
2-3-0
IMO
(International Maritime Organization)
3.1. flammable liquid
