Azido-PEG12-propargyl is a PEG-based PROTAC linker that can be used in the synthesis of PROTACs[1]. Azido-PEG12-propargyl is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups. It contains an azide group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing alkyne groups. It can also undergo ring strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing DBCO or BCN groups.