The past two "Street Chemistry" columns have focused on basic groups of hydrocarbon-derivative compounds. Rules for naming and identifying the families and determining the hazards have been mostly straightforward.
Photo by Robert Burke
Vehicle accidents may produce spills of ethylene or propylene glycol, which are used as antifreeze and cooing solutions in engines.
There are, however, other compounds that contain two or more hydrocarbon-derivative families or several different elements attached to the hydrocarbons. For the purposes of "Street Chemistry" let's refer to them as "complex hydrocarbon derivatives." These compounds are not as clear on first glance as to the family they belong to or the hazards that may be associated with them. Even so, you can still apply the information you know about the specific families or elements in the compound based on worst-case scenarios, until the compounds can be looked up in reference materials and the hazards verified.
In the compound methyl ethyl ketone peroxide, for example, there are two hydrocarbon derivative families - ketone and peroxide (organic). Ketones are flammable and narcotic, while peroxides are potentially explosive and oxidizers. By taking precautions for all of the families identified responders would be looking at the worst-case scenario.
Methyl ethyl ketone peroxide is listed in the Condensed Chemical Dictionary as being a "fire risk in contact with organic materials and a strong irritant to skin and tissue." CFR 49 Hazardous Material Table lists it as a "forbidden" commodity in transportation when the active oxygen in the compound is greater than 9%. Methyl ethyl ketone peroxide is listed in the 1996 North American Emergency Response Guide (NAERG96) as an organic peroxide/heat and contamination sensitive and a severe irritant. Manufacturer Safety Data Sheets (MSDS) indicate that the material is stable, will not undergo polymerization and is a combustible liquid.
The point I am making here is if you had taken the worst-case scenario for methyl ethyl ketone peroxide, you would have been in error. However, it is always better to err on the side of safety. Taking precautions for an organic peroxide would have protected you against this compound. Overprotection, yes, but overprotection on the side of safety is better when you don't know the exact hazards of a compound. You may be teased, have "egg on your face" or be embarrassed; however, no one has ever died from any of those things. But if you don't err on the side of safety, when you haven't verified the hazards, you could be seriously injured or die!
Photo by Robert Burke
Methyl ethyl ketone peroxide and benzoyl peroxide are Class 5.2 organic peroxide compounds that carry this type of placard in shipments.
Methyl ethyl ketone peroxide (MEKP) is most commonly found as a hardening agent for fiberglass-reinforced plastics. Under the United Nations/Department of Transportation (UN/DOT) classification systems it is a Class 5.2 Organic Peroxide. The UN four-digit identification number is 2550 and Orange Guide 147 from the NAERG96 is used for first responder information. MEKP has a boiling point of 293 degrees Fahrenheit, a flash point of >140 degrees F, is heavier than air and is listed as a combustible liquid class IIIA under the OSHA Flammability Class. Combustion products include carbon monoxide, carbon dioxide and various hydrocarbons.
Benzoyl peroxide is another compound that has the peroxide and ketone derivative families in the structure and formula. It is also listed as a UN/DOT Class 5.2 organic peroxide. The UN identification number is 2085 and Orange Guide 146 is used from the NAERG96. When wet, it is stable; when dry with less than 1% water, it may explode spontaneously. It is also highly toxic by inhalation with a TLV of 5 mg/m3 of air.
Benzoyl peroxide is a white, granular, crystalline solid that is tasteless and has an odor of benzaldehyde. There is approximately 6.5% active oxygen in the compound. It decomposes explosively above 220 degrees F and has an autoignition temperature of 176 degrees F. Benzoyl peroxide is used as a bleaching agent for flour, fats, oils and waxes and in pharmaceutical and cosmetic compounds in lower concentrations. Initially treating benzoyl peroxide as a worst-case-scenario organic peroxide would be the appropriate action. Anything less could spell disaster to first responders.
Some alcohol compounds contain more than one alcohol derivative group. For example, ethylene glycol is a common coolant and antifreeze. Ethylene glycol has two alcohol groups attached to the hydrocarbon ethene or ethylene. The compound is a clear, colorless, syrupy liquid that has a sweet taste and is odorless. Its boiling point is approximately 387 degrees F and the flash point is about 7 degrees F. Ethylene glycol is toxic by ingestion and inhalation with a TLV (vapor) ceiling of 50 ppm. The reported lethal dose by ingestion is 100 cc.
Photo by Robert Burke
This notice is posted on a railroad tank car containing ethylene glycol, a common antifreeze and cooling material from the alcohol family.
Propylene glycol also has two alcohol groups but they are attached to propene, also known as proplyene. Its physical characteristics are similar to those of ethylene glycol except that the flash point is much lower at -40 degrees F. It is also much less toxic than ethylene glycol. Some of its uses include an antifreeze, coolant in refrigeration systems, a solvent for food additives, colorings and flavorings and a de-icing fluid for airport runways.
Glycerol, also known as glycerin, is another complex alcohol. It has three alcohol groups attached to propane. It is a clear, syrupy, colorless and odorless liquid with a sweet taste. The flash point is 320 degrees F and the autoignition temperature is 739 degrees F. Toxicity is low with a mist TLV of 10 mg/m3 in air. Glycerol is used in the manufacturer of dynamite, pharmaceuticals cosmetics, and food, tobacco and liquors.
When the "H's" are removed from glycerol and three nitro groups are added to the remaining oxygen, nitroglycerin is formed. It is classified by UN/DOT as a Class 1.1 explosive and is forbidden in transportation unless desensitized. The NFPA 704 designation for nitroglycerin is Health-2, Flammability-2, Reactivity-4 and Special-0. It is listed under the UN 4-digit identification number of 0143, when desensitized it is listed under several UN identification numbers depending on the mixture and make-up of the desensitizer. Orange Guides 127 and 113 are used for desensitized material and 112 for unsensitized material.
Photo by Robert Burke
A railroad tank car carrying propylene oxide, a Class 3 flammable liquid in the ether family, would carry these warnings.
Nitroglycerin is a viscous, pale yellow liquid, with a severe explosion risk and it is highly sensitive to shock and heat. The explosive hazard of nitroglycerin far outweighs the toxicity but the toxicity should not be overlooked. It is toxic by ingestion, inhalation and skin absorption. The TLV is 0.05 ppm in air, which is very toxic! Nitroglycerin is a high explosive used in the production of dynamite, combating oil well fires, rocket propellants and a vasodilator used as a treatment for some who have heart problems.
Some of the alkyl halides are "complex" hydrocarbon derivatives that don't follow the naming rules for the family, but still carry the family characteristics. Paradichloro benzene is a benzene ring with two chlorines added and is more commonly known as "mothballs." It is classified as a Class 6.1 Poison by the UN/DOT system. The NFPA 704 designation is Health-2, Flammability-2, Reactivity-0, and Special-0. The NAERG96 Orange Guide is 152 and the UN identification number is 1592. It is a white crystal, is volatile but sublimes readily, which means it goes from a crystal or solid to a vapor without becoming a liquid. Because it produces a vapor, it is known as flash point solid with a flash point of 150 degrees F. The primary route of entry into the body is by ingestion and it is also an eye irritant having a TLV of 75 ppm in air.
Photo by Robert Burke
"Inhalation Hazard" is required to be stenciled on railroad tank cars that carry ethylene oxide. The tankers also must carry flammable gas and poison placards.
Dichlorodiphenyltrichloroethane (DDT) was at one time a pesticide frequently used as an insecticide for tobacco and cotton. It is very toxic by ingestion, inhalation and skin absorption, particularly in aqueous solution. The TLV is 1 mg/m3 in air and the residue amount is limited to 5 ppm in foods.
Ether hydrocarbon derivative compounds usually have the word ether in the name, so identification from the name is fairly easy. However, some ethers have other names associated with them and the only way to recognize them is by the formula, which still has the typical single oxygen between two hydrocarbons. For example, propylene oxide and ethylene oxide are ether compounds. Both of these ethers have a cyclic structure although propylene oxide is a liquid and ethylene oxide is a gas at room temperature.
Propylene oxide has a typical ether-like odor and is colorless. Its flash point is -35 degrees F and like most ethers it has a wide flammable range with explosive limits in air of 2% to 22%. The TLV is 20 ppm in air. Ethylene oxide is also flammable with a flash point of 0 degrees F, although it is already a gas at normal temperatures, has explosive limits of 3% to 100%, and is a dangerous fire and explosion hazard.
With a flammable range as wide as ethylene oxide there is danger of a fire occurring inside the container. It is an eye and skin irritant and a suspected carcinogen with a TLV of 1 ppm in air.
Furfural is an aldehyde but you wouldn't recognize it by the name, unless you remember that aldehydes may have an "al" ending. It is a "complex hydrocarbon derivative" with three double bonds in the structure. As you might imagine, it may polymerize upon heating! The UN/DOT hazard classification is a Class 3 Flammable Liquid. NFPA has listed a 704 designation as Health-3, Flammability-2, Reactivity-0, and Special-0. In the Orange Guide Section of the NAERG96, the listing is for Guide 132P; the "P" indicates that it may polymerize. The UN identification number is 1199. It is also a cyclic compound and is a combustible liquid with a flash point of 140 degrees F and an autoignition temperature of 797 degrees F.
Furfural is a clear liquid when pure but turns reddish-brown upon exposure to light and air. The odor is similar to that of benzaldehyde. It is absorbed through the skin, and is an eye, skin, and mucous membrane irritant. The TLV is 2 ppm in air.
Ketones may have different names that disguise the hydrocarbon derivative family each belongs to. Mesityl oxide might be taken as an ether by the oxide ending. It is, however, a ketone with a double bond in the structure. Mesityl oxide is an oily, colorless liquid, with a honey-like odor. The flash point is 90 degrees F with an ignition temperature of 652 degrees F. It is a moderate fire risk but is toxic by inhalation, ingestion and skin absorption. The TLV is listed as 15 ppm in air. Mesityl oxide is used as a solvent, paint and varnish remover, and insect repellent.
Some esters are potential polymerization hazards, while others are used as food additives and flavorings. Vanillin, which is present in the flavoring vanilla, would look like a very dangerous chemical looking at the molecular and structural formulas. It is composed of white crystalline needles with a sweet smell. It is a combustible liquid but is virtually non-toxic and is used in the manufacture of perfumes, flavoring, pharmaceuticals and as a laboratory reagent. If found in a laboratory, your first instinct might be to treat it as a danger. Even though it is really not a hazard, you would err on the side of safety!
Acrylonitrile is a hazardous material that is much worse than its name sounds - its real name is vinyl cyanide. Now you may see why scientists and others changed the name! Acrylonitrile is a colorless, migratory liquid with a mild odor. The flash point is 32 degrees F and it has rather wide explosive limits of 3% to 17% in air.
In addition to being a severe fire and explosion risk, acrylonitrile is also toxic. Its primary routes of exposure are by inhalation and skin absorption and it is a known carcinogen, with a TLV of 2 ppm. The primary use is as a monomer in plastic production and as a grain fumigant.
Chemical nerve agents which could be used as weapons by terrorists are also compounds that have several derivative families along with some other elements such as sulfur and phosphorus. They belong to families called chlorinated sulfur compounds, fluorinated organophosphorous compounds, sulfonated organo-phosphorous compounds and organo-phosphorous compounds.
Looking at the elements that make up these compounds leaves little to wonder why they are so toxic. Organophosphorous compounds themselves are pesticides and affect the central nervous system. Adding fluorine, chlorine and sulfur to the compound only increases the toxicity. VX, which is the most toxic of the nerve agents, is just such a compound. In addition to the hydrocarbons in the compound, there is oxygen, phosphorus, nitrogen and sulfur. VX has a high boiling point of 568 degrees F and a high flash point of 315 degrees F. VX has an airborne exposure limit of 0.00001 mg/m3 in air.
The naming system used in the hydrocarbon and hydrocarbon derivative columns is called the "trivial" system. This system works for compounds with five and fewer carbons. When carbon chains get longer than five, it becomes more difficult to accurately name compounds, so a system developed by the International Union of Pure and Applied Chemistry (IUPAC) is used to designate locations of elements and hydrocarbons on a chemical chain.
Robert Burke will discuss "Hazardous Materials Response: Handling The Incident" at Firehouse Emergency Services Expo '98 July 16-19 in Baltimore.
Robert Burke, a Firehouse® contributing editor, is a fire protection/hazardous materials specialist for the University of Maryland and has served on state and county hazmat response teams. Burke is a veteran of over 16 years in career and volunteer fire departments, serving as assistant chief and deputy state fire marshal. He holds an associate's degree in fire protection technology and a bachelor's degree in fire science, and is pursuing a master's degree in public administration. Burke is an adjunct instructor at the National Fire Academy and Maryland Fire and Rescue Institute, and is the author of the textbook Hazardous Materials Chemistry For Emergency Responders. He can be reached on the Internet at firstname.lastname@example.org.