Figure shows that 5 is more stable than most considered structures. This prediction has several important consequences. For example, structures 12, 13, 14 are unlikely to be the products of polymerization of 5, because such transformations are predicted to be thermodynamically unfavored. Other similar examples include structures 23 and 20, predicted to lie ~1.7 and 5.8 kcal/mol HCN above 5, respectively. Establishing that formation of 23 from 5 is not thermodynamically spontaneous is important as the former is a proposed precursor to heteropolypeptides. However, we note that our predictions do not exclude the possibility of 23 forming through other higher energy intermediates, such as the HCN trimer 4 (Δ𝐺 '() * + = -1.7 kcal/mol HCN).