{HEAD ~ Another order} of {TAIL ~ addition} involves initially contacting the electron donor with the co catalyst 
{ HEAD ~ Another order } of { TAIL ~ addition } involves initially contacting the electron donor with the co catalyst
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH