Which compound is the main antifreeze ingredient with the formula HOCH₂CH₂OH?

Ethylene glycol is the main antifreeze compound with the formula HOCH₂CH₂OH.

Ethylene glycol is a diol, an alcohol containing two hydroxyl groups. Its formula is also written C₂H₆O₂. When mixed with water, it lowers the mixture’s freezing point and raises its boiling point, helping vehicle cooling systems operate across a wider temperature range.

Automotive antifreeze is not simply pure ethylene glycol. Commercial coolant usually contains water plus corrosion inhibitors, dyes, and other additives. The concentration must be balanced: too little glycol provides insufficient freeze protection, while too much can reduce heat-transfer performance.

Ethylene glycol is highly toxic if swallowed because the body metabolizes it into acidic compounds that can cause severe organ damage. Its sweet taste has contributed to accidental and deliberate poisonings, so products require secure storage. Propylene glycol is a different compound often used where lower toxicity is especially important.