The electron donor is added directly to {HEAD ~ the mixture} of {TAIL ~ the titanium halide} and the olefin 
The electron donor is added directly to { HEAD ~ the mixture } of { TAIL ~ the titanium halide } and the olefin
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH