The path towards type V deep eutectic solvents: inductive effects and steric hindrance in the system -butanol + perfluoro -butanol

• Published in: Physical chemistry chemical physics : PCCP 2023-04, Vol.25 (16), p.11227-11236
• Main Authors: Vaz, Inês C. M, Lobo Ferreira, Ana I. M. C, Silva, Gonçalo M. C, Morgado, Pedro, Abranches, Dinis O, Bastos, Margarida, Santos, Luís M. N. B. F, Filipe, Eduardo J. M, Coutinho, João A. P
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d3cp00701d

The solid-liquid phase behaviour of two tertiary alcohols, perfluoro- tert -butanol and tert -butanol, was studied here using experimental (ITC, DSC and density measurements) and theoretical (MD simulations) approaches. The phase diagram of the binary mixture reveals highly negative deviations from ideality at low concentrations, as well as the formation of co-crystals and is characterized by two eutectic points, a congruent melting point and a peritectic reaction corresponding to TBH : TBF stoichiometries of 2 : 1 and 1 : 1 respectively. Excess molar enthalpies and volumes were calculated, showing negative and positive deviations from ideality, respectively. The effect of acidity, stereochemical hindrance and phobic effects and how they affect intermolecular interactions in these binary mixtures is discussed, with the aim of designing and fine-tuning type V deep eutectic solvents. The results showed that the fluorination of tertiary alcohols can be used for the tuning of the mixing properties and solid-liquid phase diagrams. The electron withdrawal effect of the fluorine atoms in perfluoro- tert -butanol leads to a large polarity asymmetry. This results in strong hydrogen bonding when mixed with a regular alcohol and is explored to prepare a type V deep eutectic solvent.