The range of computed ∆𝐺 ‡ for was found to be 16.5 kcal mol -1 , corresponding to t 1/2 values ranging from 10 -3 seconds to 10 5 years (nearly 12 orders of magnitude). Figure shows the transition state geometries for systems with the smallest and largest t 1/2 values for the unsubstituted and substituted thiophene rings, respectively. The shortest lifetime was for the systems with the nitro-substituted phenyl ring, and the longest lifetime was for the systems with an amine substituent on the phenyl ring. and CNN angles about the diazo bond are labelled. NNC Ph corresponds to the angle with the carbon atom in the phenyl ring, and NNC Th corresponds to the angle including the carbon atom on the thiophene rings.