Apparent molar heat capacities of n-Alcohols (C2 to C4) and symmetric Tetraalkylammonium Bromides (C2 to C5) in Water–N,N-Dimethylformamide Mixtures: Methylene Group Contribution and Hydrophobic Hydration
Waghorne, W.E., Riveros, D.C., Vargas, E.F. and Hefter, G. (2016) Apparent molar heat capacities of n-Alcohols (C2 to C4) and symmetric Tetraalkylammonium Bromides (C2 to C5) in Water–N,N-Dimethylformamide Mixtures: Methylene Group Contribution and Hydrophobic Hydration. Journal of Solution Chemistry . In Press.
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The apparent molar heat capacities, ϕ C p , of ethanol, n-propanol, n-butanol, and tetraethylammonium, tetra-n-propylammonium, tetra-n-butylammonium and tetra-n-pentylammonium bromides have been measured measured using a Picker flow calorimeter (Sodev, Canada, Model CP-Cpr) at 298.15 K in water–N,N-dimethylformamide (DMF) mixtures. The contribution of the CH2 moiety, ϕ C p (CH2), was estimated from these data as the change in ϕ C p per additional CH2 unit. The values of ϕ C p (CH2) in water (ca. 100 J·K−1·mol−1) are two to three times those in neat organic solvents (ca. 30–40 J·K−1·mol−1), consistent with a substantial contribution from hydrophobic solvation in water. In water-rich aqueous DMF solutions, ϕ C p (CH2) decreases monotonically with increasing DMF concentration, the decrease being more rapid for the n-alcohols. This trend differs significantly from that reported in the literature for highly aqueous mixtures of t-butanol, where ϕ C p (CH2) passes through a maximum.
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|Murdoch Affiliation:||School of Engineering and Information Technology|
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