Lithiated hydrocarbons, their conjugate bases, and corresponding radicals:: A computational study of RLi (R = CH3, CH3CH2, CH2=CH, and HCC)

Organolithium compounds RLi (R = CH3, CH3CH2, CH2=CH, and HCequivalent toC) 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) a-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 alpha- and beta-C-H bonds, the latter by similar to-25 kcal mol(-1). Consequently, radical chemistry of lithiated compounds at remote sites is a promising area for exploration.