Propargyl-PEG2-CH2COOH is a PEG-based PROTAC linker that can be used in the synthesis of PROTACs. Propargyl-PEG2-CH2COOH is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.