ar ▁and ▁prot ic ▁sol vent s ▁interact ▁with ▁the ▁hydro gen ▁b onds ▁and ▁more ▁mon omer ▁is ▁formed . ▁H ydro ph ob ic ▁effects ▁in ▁non - pol ar ▁sol vent s ▁lead ▁to ▁a ▁pre domin ance ▁of ▁the ▁dim er . ▁The ▁ratio ▁of ▁the ▁t aut omer ic ▁forms ▁is ▁also ▁dependent ▁on ▁the ▁sol vent . ▁All ▁possible ▁t autom ers ▁and ▁dim ers ▁can ▁be ▁present ▁and ▁form ▁an ▁equilibrium , ▁and ▁the ▁exact ▁measurement ▁of ▁all ▁the ▁equilibrium ▁constants ▁in ▁the ▁system ▁is ▁extremely ▁difficult . ▁ ▁( N MR - spect ro sc opy ▁is ▁a ▁slow ▁method , ▁high ▁resolution ▁IR - spect ro sc opy ▁in ▁sol vent ▁is ▁difficult , ▁the ▁broad ▁absor ption ▁in ▁U V - spect ro sc opy ▁makes ▁it ▁hard ▁to ▁disc rim inate ▁ 3 ▁and ▁more ▁very ▁similar ▁mole cules ). ▁ ▁Some ▁publications ▁only ▁focus ▁one ▁of ▁the ▁two ▁possible ▁patterns , ▁and ▁neglect ▁the ▁influence ▁of ▁the ▁other . ▁For ▁example , ▁to ▁calculation ▁of ▁the ▁energy ▁difference ▁of ▁the ▁two ▁t autom ers ▁in ▁a ▁non - pol ar ▁solution ▁will ▁lead ▁to ▁a ▁wrong ▁result ▁if ▁a ▁large ▁quantity ▁of ▁the ▁subst ance ▁is ▁on ▁the ▁side ▁of ▁the ▁dim er ▁in ▁an ▁equilibrium . ▁ ▁T aut omer isation ▁mechanism ▁B ▁The ▁direct ▁t aut omer isation ▁is ▁not ▁ener get ically ▁fav oured , ▁but ▁a ▁dim er isation ▁followed ▁by ▁a ▁double ▁pro ton ▁transfer ▁and