This chemical is primarily used in bioconjugation and protein modification processes. It acts as a reactive ester, facilitating the attachment of polyethylene glycol (PEG) chains to biomolecules such as proteins, peptides, or antibodies. The PEGylation process enhances the stability, solubility, and circulation time of these biomolecules in biological systems, making it valuable in therapeutic applications. Additionally, it is employed in the development of drug delivery systems, where PEGylation can improve the pharmacokinetics and reduce immunogenicity of drugs. Its structure, featuring a chloro group and an activated ester, allows for efficient and selective conjugation under mild conditions, making it a useful tool in biochemical research and pharmaceutical development.