Enthalpies of solution of tetra-alkylammonium salts in hexamethylphosphotriamide at 298.15 K

Abstract

The enthalpies of solution of some tetra-alkylammonium salts and of tetraphenylphosphonium bromide in hexamethylphosphotriamide (HMPT) at 298.15 K have been obtained. Ionic enthalpies of transfer from water to HMPT and from HMPT to propylene carbonate (PC) have been calculated on the basis of the extrathermodynamic assumption ΔH^°_tr(Ph₄As⁺)=ΔH^°_tr(BPh^–₄). The results indicate that this assumption is valid for enthalpies of transfer from HMPT to PC, but not for transfer from water to HMPT. The enthalpies of transfer of tetra-alkylammonium ions from HMPT to PC are discussed in terms of the ability of HMPT to solvate alkyl chains.