Finally, we consider whether a given transformation appears thermodynamically feasible. A very large positive change in Gibbs free energy of reaction (Δ𝐺 𝑅 ∘ ) might be used to discount a suggested transformation initially. Doing so for the top three-ranking transformations yields Δ𝐺 𝑅 ∘ of 124 kcal mol -1 , -139 kcal mol -1 , and -148 kcal mol -1 . The first transformation thus has a very large positive Δ𝐺 𝑅 ∘ making it highly non-spontaneous under the assumptions used perhaps providing reason to discount it. The other two reactions do not have this problem.