Lithiated Hydrocarbons, Their Conjugate Bases, and Corresponding Radicals: A Computational Study of RLi (R = CH₃, CH₃CH₂, CH₂=CH, and HC≡C)

Organolithium compounds RLi (R = CH₃, CH₃CH ₂, CH₂=CH, and HC≡C) and their corresponding hydrocarbons were fully optimized at the MP2/6-311+G(2df,2pd) level. Single-point energy calculations also were carried out at the CCSD(T) and B3LYP levels with the same triple split-valence basis set. Acidities, electron affinities, and bond dissociation energies are reported, and the following general results were found: (1) α-Lithio anions are ground-state triplet molecules. (2) Lithium is an acid-enhancing substituent. (3) Conjugate bases of organolithiums are stable with respect to electron loss and therefore are attractive targets for mass spectrometry investigations. (4) Lithium weakens α- and β-C-H bonds, the latter by ∼25 kcal mol^-1. Consequently, radical chemistry of lithiated compounds at remote sites is a promising area for exploration.