Some thermodynamic parameters for substituted ammonium salts of the tetramethoxyborate anion

Abstract

Thermodynamic parameters for the formation of piperidinium tetramethoxyborate from piperidine, trimethoxyborane, and methanol are presented. The results show that the formation of the salt is due to a favourable enthalpy change, the standard entropy change being negative. The fact that similar salts with larger tetra-alkoxyborate anions are thermodynamically unstable is discussed. The derived enthalpy of formation of piperidinium tetramethoxyborate ΔH_f° C₅H₁₂NB(OMe)₄(s)=–1310·91 ± 1·72 kJ mol^–1. The derived enthalpy of formation of 2-aminoethylammonium tetramethoxyborate ΔH_f°enH B(OMe)₄(s)=–1266·5 ± 1·5 kJ mol^–1 and of ethylenediammonium ditetramethoxyborate ΔH_f°enH₂[B(OMe)₄]₂(s)=–2486·0 ± 2·0 kJ mol^–1.