Hydroxyethyl

Hydroxyethyl refers to a two-carbon hydroxy-substituted ethyl substituent, typically represented as -CH2-CH2-OH and attached to a parent molecule through the first carbon. It is commonly called a 2-hydroxyethyl group.

The hydroxyethyl substituent is typically introduced by ethoxylation, the reaction of a substrate with ethylene oxide. The resulting 2-hydroxyethyl group is attached to the substrate via the CH2 group, yielding mono-, di-, or polyhydroxyethyl derivatives depending on the number of ethylene oxide units added. The introduction increases polarity and water solubility and can modify reactivity, hydrogen bonding, and biocompatibility.

Common derivatives and uses: Hydroxyethyl cellulose (HEC) is a water-soluble thickener and binder used in foods, cosmetics, pharmaceuticals, and papermaking. Hydroxyethyl starch (HES) is used as a colloid for plasma-volume expansion in medicine, though its use is subject to safety reviews. Hydroxyethyl methacrylate (HEMA) is a widely used monomer for dental resins, hydrogels, and soft tissues such as contact lenses.

Production and safety: The ethoxylation process uses ethylene oxide, a hazardous and carcinogenic agent; facilities control residuals to acceptable levels. Hydroxyethyl derivatives vary in biocompatibility and environmental fate, so applications are governed by product-specific regulations.

See also: hydroxyethyl group, ethoxylation.