Thermophysic comparative study of two isomeric pyridinium-based ionic liquids

Area of Science:

• Physical Chemistry
• Materials Science

Background:

• Room-temperature ionic liquids (RTILs) are tunable solvents with unique properties.
• Isomeric RTILs, like pyridinium-based compounds, offer subtle differences in structure and behavior.

Purpose of the Study:

• To conduct a comprehensive thermophysical characterization of n-butyl-3-methyl-pyridinium tetrafluoroborate and n-butyl-4-methyl-pyridinium tetrafluoroborate.
• To analyze the impact of structural isomerism on thermophysical properties.
• To evaluate the predictive accuracy of various theories and empirical relations for these RTILs.

Main Methods:

• Experimental determination of density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, and kinematic viscosity.
• Calculation of thermal expansion coefficients, dynamic viscosities, and molar refractions.
• Application and comparison of several theoretical and empirical models for property prediction.

Main Results:

• Detailed thermophysical data for the two isomeric ionic liquids were obtained.
• Structural differences between isomers were correlated with observed property variations.
• Good agreement was found between experimental and predicted physical properties.
• Density and coefficients of thermal expansion showed particularly good predictability.

Conclusions:

• The study provides valuable thermophysical data for specific pyridinium-based RTILs.
• Predictive models are effective for certain properties, aiding in RTIL design and application.
• Understanding isomer-specific properties is crucial for targeted material development.