Chloroethane, often called ethyl chloride, is a chemical compound commonly used in industrial and medical settings. It is a colorless, highly flammable gas at room temperature and pressure, possessing the chemical formula \(\text{C}_2\text{H}_5\text{Cl}\). It has a long history of use, ranging from industrial applications to its former role as a general anesthetic. Its use requires careful consideration of its inherent hazards.
Chemical Identity and Physical Characteristics
Chloroethane is an organochlorine compound containing carbon, hydrogen, and a single chlorine atom bonded to an ethyl group. Under normal atmospheric conditions, it exists as a gas, but it is typically stored as a compressed, colorless liquid. The compound has a low boiling point of approximately \(12.3^\circ\text{C}\) (\(54^\circ\text{F}\)), causing the liquid to evaporate rapidly when released.
The gaseous form of chloroethane is heavier than air and can accumulate in low-lying areas. It has a distinct, sharp, and slightly sweet ether-like odor. Chloroethane is highly flammable; its vapor can easily ignite and cause pressurized containers to rupture when exposed to heat. Due to its volatility and low boiling point, the liquid form causes immediate cooling upon contact, which is leveraged for medical use.
Industrial and Medical Applications
Historically, chloroethane was used as an intermediate in the manufacture of tetraethyl lead, an anti-knock agent added to gasoline. The phase-out of leaded gasoline significantly reduced this industrial demand. Today, chloroethane remains relevant as a solvent in the production of ethyl cellulose, a thickening agent found in paints and cosmetics. It also functions as a chemical intermediate in the synthesis of various dyes, pharmaceuticals, and other commercial chemicals.
In the medical field, chloroethane is used as a localized topical anesthetic. When sprayed onto the skin, the liquid’s rapid evaporation absorbs heat from the surface, causing a deep chill. This rapid cooling numbs the skin and underlying tissue, providing temporary pain relief for minor procedures like ear piercing, skin biopsies, or treating muscle pain and sports injuries. Although it was once employed as a general inhalation anesthetic, this practice was discontinued due to the narrow margin between effective and toxic doses.
Human Health Risks and Safety
Exposure to chloroethane primarily occurs through inhalation of the vapor, which acts as a central nervous system depressant. Breathing high concentrations can rapidly induce symptoms similar to alcohol intoxication, including dizziness, slurred speech, and lack of muscle coordination. At higher levels, the vapor can lead to unconsciousness and death, often due to irregular heart rhythms and respiratory failure, a risk demonstrated during its former use as a general anesthetic.
Intentional inhalation of chloroethane, a form of substance abuse, is particularly dangerous because high concentrations quickly lead to fatal cardiac events. Direct contact with the liquefied form poses the risk of severe localized frostbite and tissue damage due to rapid evaporation. While acute effects are well-documented, the long-term health consequences of low-level, chronic exposure in humans are not fully understood.
Animal studies indicate that long-term exposure can cause adverse effects on organs such as the lungs, liver, kidneys, and heart. Regarding cancer risk, the evidence is mixed; some animal studies suggest a link to carcinogenicity, but the International Agency for Research on Cancer (IARC) has determined that chloroethane is not classifiable as carcinogenic in humans. Safe handling requires robust ventilation systems to control vapor concentrations and the use of protective equipment to minimize skin and eye contact.