Allyl-lithium: a rapidly equilibrating, unsymmetrical dimer in tetrahydrofuran

Abstract

Cryoscopic measurements and variable temperature ¹³C n.m.r. studies on isotopically perturbed samples show allyl-sodium and allyl-potassium to have symmetrical structures, but allyl-lithium to be an unsymmetrical dimer in tetrahydrofuran; this association explains the discrepancy between the observed rotational barrier (10.7 kcal/mol) and that calculated for the isolated allyl-lithium monomer (17.7 kcal/mol)(1cal = 4.184J).