By {HEAD ~ a cationic Lewis acid} is meant {TAIL ~ a cation} with a positive charge such as Ag+, H+, and Na+ 
is meant
By { HEAD ~ a cationic Lewis acid } is meant { TAIL ~ a cation } with a positive charge such as Ag+ , H+ , and Na+
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH