Used primarily as an activating agent in organic synthesis, especially in the preparation of esters and amides. It facilitates the coupling of carboxylic acids with alcohols or amines under mild conditions. The presence of the 4-nitrophenyl and 1-chloroethyl groups enhances its reactivity and leaving group ability, making it effective in peptide synthesis and other acyl transfer reactions. Commonly employed in pharmaceutical manufacturing where selective and efficient esterification is required. Due to its lability, it is typically used in situ and handled under anhydrous conditions.