Cl-PEG6-acid is widely used in bioconjugation and chemical synthesis due to its reactive functional groups. The terminal chlorine atom allows for nucleophilic substitution reactions, making it useful for attaching to various molecules, such as proteins, peptides, or small molecules. The PEG (polyethylene glycol) spacer enhances solubility and reduces immunogenicity, making it valuable in drug delivery systems and therapeutic applications. The carboxylic acid group enables further conjugation through amide bond formation, facilitating the creation of complex biomaterials or targeted drug carriers. It is also employed in surface modification, where it can be used to functionalize nanoparticles or other materials for biomedical research. Its versatility makes it a key component in developing biocompatible and functionalized compounds.