Azide PEG

PEG azide or Azido PEG is widely used in
a) Click Chemistry, the particular example of the Cu(I) catalyzed reaction of the azide and a terminal acetylene; and
b) the Staudinger ligation using functionalized aryl phosphines to couple the azide in a covalent fashion to form amides. The attraction of the azide functionality is its high selectivity and stability under most conditions, especially where other conjugating functionalities have to be used due to their limited stability, or when careful control of variables, like pH, are required in order to insure high yielding reactions.