Ethyl chloride is a chemical compound used both as a medical agent and an industrial precursor. It is a colorless, highly flammable gas at room temperature, though it is often stored and sold as a liquid under pressure in aerosol cans. The compound has a distinct, sweet, and faintly ether-like odor. Applications range from a fast-acting topical anesthetic in sports medicine to a reactant in large-scale chemical manufacturing.
Chemical Identity and Physical Properties
Ethyl chloride is chemically known as chloroethane, an organohalide with the chemical formula C2H5Cl. It possesses a low boiling point of approximately 12.3°C (54.1°F). This low boiling point means the liquid rapidly transitions to a gas upon release at normal temperatures.
As a chlorinated hydrocarbon, ethyl chloride is highly flammable, forming explosive mixtures with air at concentrations between 3.8% and 15.4% by volume. It is readily soluble in organic solvents, such as alcohol and ether, but only slightly soluble in water. The compound is stable but can decompose when exposed to heat, light, or water, especially near certain metals.
Primary Medical Use as a Topical Anesthetic
Ethyl chloride is primarily used as a topical anesthetic, supplied in a spray form. It operates on the principle of cryoanesthesia, or temporary numbing by cold. When the pressurized liquid is sprayed onto the skin, its rapid evaporation draws a significant amount of heat away from the surface.
This chilling effect causes the skin temperature to drop dramatically, sometimes reaching as low as -20°C. The sudden cold temporarily blocks the sensitivity of peripheral nerve endings, providing a brief, localized numbing sensation. The temporary anesthesia typically lasts for only 30 to 60 seconds following a short application.
It is frequently used in sports medicine for immediate, short-term relief of minor muscle spasms, bruises, or contusions, often utilizing the “spray and stretch” technique. It is also employed to numb the skin before minor procedures, such as blood draws or minor incisions. Risks include the brief duration of the numbing effect and the potential for chemical frostbite from prolonged spraying.
Industrial and Historical Applications
Historically, ethyl chloride was used in large-scale industrial processes, primarily as a precursor in the manufacture of tetraethyl lead (TEL). TEL served as the primary antiknock agent added to gasoline for decades.
The production of TEL involved reacting ethyl chloride with a lead-sodium alloy. Following global phase-outs of leaded gasoline, which began in the 1970s, demand for ethyl chloride in this process drastically decreased. Today, its largest industrial use is as a reactant in the production of ethyl cellulose, a polymer used in coatings, films, and pharmaceutical binders.
The compound has also been used as a solvent for materials like phosphorus, oils, and resins, and was historically used as a refrigerant. Other applications include serving as an intermediate in the synthesis of various dyes and pharmaceuticals.
Health Risks, Misuse Potential, and Regulation
Ethyl chloride presents health hazards, particularly through inhalation. The compound acts as a central nervous system (CNS) depressant, meaning it slows down brain activity. Low-level exposure can cause transient effects like euphoria, dizziness, and intoxication.
Inhalation of higher concentrations, often associated with intentional misuse or inhalant abuse, can lead to severe neurotoxicity. The effects progress to lack of muscle coordination, impaired memory, and unconsciousness. Chronic exposure may result in tremors and difficulty with speech.
Misuse carries the potential for adverse cardiovascular effects, including irregular heart rhythms. This risk is compounded by “Sudden Sniffing Death Syndrome,” where a person dies suddenly after inhaling volatile substances. Long-term or heavy exposure has also been associated with damage to the liver and kidneys, and animal studies have indicated carcinogenicity.
Due to its flammability and potential for misuse, ethyl chloride is subject to various regulations. The medical spray is regulated by bodies like the Food and Drug Administration (FDA) for controlled, external application. Safety protocols require avoiding inhalation and applying it only for short durations to minimize systemic exposure and frostbite risk.