Ethylene Glycol
Introduction
Ethylene glycol, also known by its IUPAC name ethane-1,2-diol, is a colorless, odorless, and sweet-tasting organic compound with the formula (CH2OH)2. It is primarily used as an automotive antifreeze and a precursor to polymers. Ethylene glycol is toxic and ingestion can lead to serious health issues, including kidney failure and death.
Chemical Properties
Ethylene glycol is a dihydric alcohol, meaning it contains two hydroxyl groups (-OH). Its molecular weight is 62.07 g/mol, and it has a boiling point of 197.3 °C and a melting point of -12.9 °C. The compound is miscible with water, alcohols, and many other organic solvents. Its chemical structure allows it to participate in hydrogen bonding, which contributes to its high boiling point relative to its molecular weight.
Production
Ethylene glycol is industrially produced from ethylene via the intermediate ethylene oxide. Ethylene oxide reacts with water to produce ethylene glycol according to the following reaction:
\[ \text{C}_2\text{H}_4\text{O} + \text{H}_2\text{O} \rightarrow \text{HOCH}_2\text{CH}_2\text{OH} \]
This reaction is typically catalyzed by either acid or base catalysts. The process can yield different grades of ethylene glycol, including monoethylene glycol (MEG), diethylene glycol (DEG), and triethylene glycol (TEG).
Applications
Automotive Antifreeze
One of the primary uses of ethylene glycol is as an antifreeze in automotive cooling systems. It lowers the freezing point of water and raises its boiling point, which helps to prevent the engine from freezing in cold temperatures and overheating in hot temperatures. Ethylene glycol-based antifreeze is usually mixed with water in a 50:50 ratio.
Industrial Applications
Ethylene glycol is also used in the production of polyester fibers and resins. Polyethylene terephthalate (PET), a common polyester, is synthesized from ethylene glycol and terephthalic acid. PET is widely used in the manufacture of plastic bottles, food packaging, and textile fibers.
Deicing Solutions
Ethylene glycol is employed in deicing solutions for aircraft and runways. Its ability to lower the freezing point of water makes it effective in preventing the formation of ice on critical surfaces.
Toxicity and Safety
Ethylene glycol is highly toxic if ingested. It is metabolized in the body to glycolic acid and oxalic acid, which can cause metabolic acidosis, renal failure, and central nervous system depression. Symptoms of ethylene glycol poisoning include nausea, vomiting, convulsions, and coma. Immediate medical attention is required for suspected cases of ingestion. The use of ethylene glycol in consumer products is regulated to minimize the risk of accidental poisoning.
Environmental Impact
The release of ethylene glycol into the environment can have detrimental effects on aquatic life due to its toxicity. It is biodegradable, but its breakdown products can still pose environmental hazards. Proper disposal and treatment of ethylene glycol waste are essential to mitigate its environmental impact.
Chemical Reactions
Ethylene glycol can undergo various chemical reactions due to the presence of its hydroxyl groups. It can be oxidized to produce oxalic acid, glycolic acid, and glyoxylic acid. It can also participate in esterification reactions to form glycol esters, which are used as solvents and plasticizers.
See Also
References
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