Probing the influence of stereoelectronic effects on lithium affinity in 1,3-and 1,4-dioxa systems

A combined computational and structural study of the lithium affinity (LA) of O-C-O systems exhibiting the anomeric effect and of O- C-C-O systems exh ibiting the gauche effect is presented. QM ab initio calculations using the MP2/6-31G* basis set were carried out on the gas-phase lithium affinities of dimethoxymethane (DMOM), dimethoxyethane (DMOE), 1,3-dioxane (DOX) and c is- and trans-tetraoxadecalin (TOD), along with that of dimethyl ether and of its dimer as reference compounds. Structural parameters were retrieved f rom the Cambridge Structural Database (CSD) for diethyl ether dimer and O-C -C-O lithium complexes and these agreed well with the calculated data. The computed lithium affinities of dimethoxymethane and dimethoxyethane were fo und to be conformationally dependent. The LAs are conformationally dependen t (wherever applicable) and decrease in the order: (Me2O)(2) > DMOE > DMOM > DOD > DOX > trans-TOD, but cis-TOD restores the high LA (better than DMOE ) by virtue of multiple coordination. Copyright (C) 2001 John Wiley & Sons, Ltd.