Phenol, also known under an older name of carbolic acid, is a toxic, colourless crystalline solid with a sweet tarry odor. It is a significant component in the aroma of Islay scotch whisky.^[1] Its chemical formula is C₆H₅OH and its structure is that of a hydroxyl group (-OH) bonded to a phenyl ring; it is thus an aromatic compound.

Phenol has a limited solubility in water (8.3 g/100 ml). It is slightly acidic: The phenol molecule has weak tendencies to lose the H⁺ ion from the hydroxyl group, resulting in the highly water-soluble phenoxide anion C₆H₅O⁻. Compared to aliphatic alcohols, phenol shows much higher acidity;

Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound (a diol alcohol), usually a faintly sweet, odorless, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform.

Industrially propylene glycol is produced by propylene oxide hydration. Different manufacturers use non-catalytic high-temperature process at 200-220 °C or catalytic route which proceeds at 150-180 °C in presence of ion exchange resin or small amounts of sulfuric acid or alkali.

Ethylene glycol (monoethylene glycol (MEG), 1,2-ethanediol, IUPAC name: ethane-1,2-diol) is an alcohol with two -OH groups (a diol), a chemical compound widely used as an automotive antifreeze. In its pure form, it is an odorless, colorless, syrupy liquid with a sweet taste. Ethylene glycol is toxic.

Ethylene glycol is produced from ethylene, via the intermediate ethylene oxide. Ethylene oxide reacts with water to produce ethylene glycol according to the chemical equation