Toluene is a non-polar aromatic solvent widely used in biochemistry for the extraction of hydrophobic molecules such as lipids and pigments. It is also employed in polymer chemistry and chromatographic procedures, particularly for dissolving polystyrene materials during gel filtration analyses.
Chemical Properties
Toluene (C6H5CH3 or C7H8) is composed of a benzene ring substituted with a methyl group. The aromatic ring carbons are sp²-hybridized, with a C–C bond length of approximately 0.1399 nm, while the methyl carbon is sp³-hybridized, forming a C–CH3 bond of about 0.1524 nm.
This solvent has a boiling point of 110.6°C and a freezing point of −95°C. Its density is approximately 0.867 g/mL, and it exhibits very low aqueous solubility (<0.05 g/100 mL), supporting biphasic extraction systems. The dipole moment is about 0.36 D, and its ultraviolet absorption cutoff is near 260 nm, making it suitable for certain spectroscopic applications.
Biochemical Applications
In lipid biochemistry, toluene is used to extract neutral lipids and carotenoid pigments from plant tissues following Folch-type extraction procedures, or to elute triglycerides in column chromatography as an alternative to hexane when stronger solvation of aromatic compounds is required.
It can also solubilize membrane proteins for SDS-PAGE sample preparation or dissolve polystyrene beads in size-exclusion chromatography used for glycoprotein fractionation.
In molecular biology workflows, anhydrous toluene may be used to dry DNA pellets or remove residual mineral oil from amplification reactions without introducing analytical interference.