Since {TAIL ~ this reaction} is ArNH2+NO2 −+2H+→ArN2 ++2H2O, it theoretically requires two equivalents of {HEAD ~ an acid} 
Since { TAIL ~ this reaction } is ArNH2+NO2 −+2H+→ArN2 + +2H2O , it theoretically requires two equivalents of { HEAD ~ an acid }
OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD