Apparent molal volumes of symmetrical and asymmetrical isomers of tetrabutylammonium bromide in water at several temperatures

Apparent molal vols. of a series of differently substituted quaternary ammonium bromides, namely tetra-​iso-​butyl-​, tetra-​sec-​butyl-​, tetra-​n-​butyl-​, di-​n-​butyl-​di-​sec-​butyl- and di-​n-​butyl-​di-​iso-​butylammonium bromide have been detd. as a function of molal concn. at (298.15, 303.15 and 308.15) K. Partial molar volumes at infinite diln. and ionic molar volumes of these quaternary ammonium cations were detd. Structural vol. contributions to the ionic molar volume were also calcd. The sym. and asym. quaternary ammonium cations are "structure making" ions. The contribution of the branched Bu chains predominates over the linear Bu chains in the asym. cations.