carboxymethylated

Carboxymethylated is a term used to describe a molecule that has been modified by carboxymethylation, the introduction of carboxymethyl groups (-CH2-COO−) into available functional sites such as hydroxyl groups on polysaccharides or amine groups on proteins. In polysaccharides like cellulose, starch, or chitosan, carboxymethylation forms carboxymethyl ethers. These derivatives are typically water-soluble and carry a negative charge at neutral and alkaline pH due to the carboxylate groups.

The synthesis commonly involves reaction with monochloroacetic acid or its salt in a basic medium (e.g., sodium hydroxide), under controlled temperature and time. The degree of substitution (DS) indicates the average number of hydroxyl (or other) sites substituted per monomer unit and affects solubility, swelling, and rheology. Purification includes washing, neutralization, and drying.

The best-known example is carboxymethyl cellulose (CMC), but carboxymethylation is applied to starch, chitosan, pectin, and other polymers. Applications span food as thickeners and stabilizers; pharmaceutical and cosmetic excipients; paper and textile processing; and controlled-release formulations and hydrogels in biomedical contexts.

Properties vary with DS and molecular weight; higher DS generally increases solubility and negative charge, while rheological properties provide thickening or gelling effects. The term encompasses a family of derivatives rather than a single compound, and its use depends on the base polymer and intended application.