Chemical Structure**: Ethylene Glycol has the chemical formula C2H6O2. It is a simple diol with two hydroxyl (-OH) groups attached to a two-carbon (C2) chain. Antifreeze and Coolant**: Ethylene Glycol is best known as the primary ingredient in automotive antifreeze and engine coolant. It helps prevent freezing and overheating of engines. Heat Transfer Fluid**: It is also used as a heat transfer fluid in HVAC systems, solar water heaters, and other industrial cooling applications. Deicing Agent**: Ethylene Glycol is used in deicing solutions for aircraft and runways at airports to prevent ice buildup. Plastics and Resins**: It is used in the production of polyester resins, which are used in the manufacture of bottles, fibers, and various plastic products. Solvent**: Ethylene Glycol can act as a solvent for dyes, inks, and various chemical processes. Toxicity**: While useful, Ethylene Glycol is highly toxic if ingested and poses health risks, so proper handling and disposal are essential.

**Diethylene Glycol:**

Chemical Structure**: Diethylene Glycol (DEG) has the chemical formula C4H10O3. It contains two ethylene glycol units connected by an oxygen atom. Solvent and Chemical Reactions**: DEG is used as a solvent for various applications, including as a plasticizer in the production of plastics, resins, and adhesives. It can also be used in chemical reactions as a reagent. Deicing and Antifreeze**: Like ethylene glycol, DEG has deicing properties and is used in some antifreeze formulations. Toxicity**: Diethylene Glycol is also toxic if ingested, and there have been incidents of mass poisonings in the past due to its mistaken use in pharmaceuticals. This has led to increased regulation and scrutiny of its use. Hygroscopic Properties**: DEG has hygroscopic properties, meaning it can absorb moisture from the air. This makes it useful in some applications, such as as a desiccant in gas drying. Manufacturing**: DEG is produced through the ethylene glycol process and is a co-product along with monoethylene glycol (MEG).

In summary, Ethylene Glycol and Diethylene Glycol are important chemicals used in various industrial applications, primarily as antifreeze, coolants, and solvents. However, their toxicity necessitates careful handling and regulation to prevent health hazards.