Tetrabutylammonium bromide (TBAB) is a quaternary ammonium compound. It is the most widely used phase transfer catalyst. Its interfacial properties have been studied in case of hydroxide initiated reactions. This may be applied in understanding the mechanism of phase transfer reactions. TBAB is reported to decrease retention time and remove peak tailing by acting as an ion pair reagent during the chromatographic analysis of quaternary ammonium compounds. In the molten state TBAB behaves like an ionic liquid which is a promising green alternative to organic solvents in organic synthesis. Its molar heat capacity, entropy and free energy function have been determined.