2-Naphthol: Polarity; Solubility and Uses

Polarity of 2-Naphthol

2-Naphthol is a colourless crystalline solid that is an isomer of 1-naphthol, differing in the position of the hydroxyl group on the naphthalene. 2-Naphthol is a polar molecule. Polar molecules are slightly positive at one end and slightly negative at the other. These opposite charges allow the molecule to attract other polar substances similar to a magnet. The positive pole on a magnet is attracted to the negative pole of another magnet.

Since naphthol contains hydroxyl groups, it is a very polar molecule, and the oxygen atom attracts the electron density to itself through bonds. For a molecule to be polar requires a difference in electronegativity (the ability of an atom to attract electrons) between one or more atoms, and in the case of naphthol, oxygen is more electronegative than carbon and hydrogen. As a result, it can "take up" more electron density using bonds, making it polar.

Solubility of 2-Naphthol

2-Naphthol is able to form strong hydrogen bonds due to the hydroxyl functional group. Hydrogen bonding is a special type of bonding in which hydrogen bonds from one compound are combined with highly electronegative atoms (atoms that attract electrons), such as nitrogen, oxygen and fluorine from another compound. This hydrogen bonding also makes naphthol soluble in alcohol-based solvents (including ethanol, methanol and isopropanol) and slightly soluble in water.

Uses of 2-Naphthol

The main use of 2-naphthol is in the manufacture of dyes and pigments. It is used as a fungicide, insecticide, preservative, medicine and flavouring; it is also used as an antioxidant in rubber, fats and oils; it is used for the lubrication of turbines, electric motors, hydraulic equipment and instruments; and its derivatives are used in the production of azo dyes. These are organic compounds containing a pair of bonded nitrogen atoms.