Used primarily as an alkylating agent in organic synthesis, particularly in the preparation of heterocyclic compounds and pharmaceuticals. It serves as a key intermediate in the synthesis of dyes, fragrances, and certain anti-inflammatory agents. Also employed in biochemical research to modify thiol groups in proteins and enzymes, aiding in the study of enzyme activity and structure. Its reactivity makes it useful in the development of specialty chemicals and in electrophilic substitution reactions. Handle with care due to its lachrymatory and corrosive properties.