Effect of N ‐substituents on the 13 C NMR parameters of azoles

The 13 C chemical shifts and a large collection of coupling constants have been measured for 169 N ‐substituted azoles with no other substituents on the ring. Simple additive models have been used to discuss both the chemical shifts and the coupling constants. The chemical shift of the substituent depends on the nature of the azole which can, accordingly, be classified into three to six families. Some structural problems (ring‐chain isomerism of 1‐trifluoromethylsulphonyl‐1,2,3‐triazole, silylotropy and stannotropy) are also discussed.