In 1907 Knuflcr concluded that ccrtnin condcnsntion reactions of bcnzidinc observcd by prcrious worlrcrs pointcd to R dcfinitc s p c c iorniuln for diplicnyl (I), in which thc two bcnzcnc nuclei wcrc so plriced tliat the corrcsponcling positions in tlieni wcrc eqiiidistnnt.
Cniii's discovcry (1 912) tlint tlicrc were two orlhorliiiitrobciizicliiics wiis rcnclily esplnincd by !ne:ins of tlic ICnuflcr forniiih, assuming no frcc rotntion nhout tlic centml IJond. Tlms :B:uidrowski?s diiiitrobeiizidiire, obtnincd froin diphtlinlyll~enzidiiic, conld bc rcgnrdcd :IS the 3 : 3'-isonicridc (11), iind Strnlcosch's dinit,robenzidinc, obtnincd froin di:icctylbcnzidiiic, as tlic 3 : B'-conipound(TII). Wlicn tliesc two dinitro-conipoiiiitls were rcducerl, two tetrn-amines rcsultcd diicli gave \yh:it WIS n11l)iirclitl-y tlic Silllic qiiinosnlinc. This nppenred to establish t . 1 ~ orientation of the two &nitro-I)cnzidiiicu, but Ctiiii \vns unable to cffcct their interconversion-a serious oLjcctio11 to his cspla~iiition. II'hen, lntcr on, I ~O W C V C ~, thc sninc iluthor described tlie isolation of two orl~o-clinitrotolidincs, oiie of wIiicIi could be converted into the other, the new isoincrisni ~I ~~c ~I ~c c I to be thorouglily estnlilislicd. At nbout; tlh time, King pointcd out thnt Stritkoscli's tlinitrobeiizidinc, if it csistiiig in two cn:intioin,cric forins.
Cniii nlso attcniptcd to test tlic rulidity of the IUltl be ctl1)ilhblc I J f " F "-clinitrodiphcnic acid, from tho bnrium snlt of which