Equilibration of lithium alkoxyaluminates derived from n-butyl, s-butyl, and t-butyl alcohols studied by 27Al nuclear magnetic resonance

Abstract

LiAlD₄ in tetrahydrofuran was titrated with solutions of n-butyl, s-butyl, and t-butyl alcohols in tetrahydrofuran. The reactions were followed by ²⁷Al and ¹³C n.m.r. In all three cases, LiAlD₄ was present in large amounts when 1 mol equiv. of alcohol had been added. The establishment of equilibria was verified by back titrations. Computer fittings to experimental ²⁷Al n.m.r. data of a proposed model for disproportionation of alkoxyaluminates, leading to re-formation of LiAlD₄, were performed. Strong support is presented for this model in the case of t-butyl alcohol. Experimentally derived LiAlD₄ concentrations can be explained in the same way in the case of n- and s-butyl alcohols. In all three cases, disproportionation of the monoalkoxyaluminates to a high degree and in the dialkoxyaluminates to a much lower degree was indicated.