Excess partial molal heat capacities of Bu4NBr in water from 4 to 70°C and the effect on the water structure

Abstract

The integral heats of solution, ΔH_s, of Bu₄NBr in water, determined from 45 to 75°C, have been combined with integral heats of solution from 3 to 35°C reported earlier to derive excess partial molal heat capacities, C^°_p^E, of Bu₄NBr in water from 4 to 70°C. C^°_p^E decreases from 4 to 25° but remains unchanged from 25° to 70°C. The temperature dependence of C^°_p^E for Bu₄NBr in water is discussed in terms of the structural changes occurring in solution. Comparison of the temperature dependence of C^°_p^E for aqueous solutions of Bu₄NBr with that for aqueous solutions of NaBPh₄ shows that non-polar groups of aliphatic hydrocarbons affect water structure differently from those of aromatic hydrocarbons. An attempt has been made of explain this difference.