Toxicological Review for 2-Methylnaphthalene (CAS No. 91-57-6 ...

2. CHEMICAL AND PHYSICAL INFORMATION RELEVANT TO ASSESSMENTS
2-Methylnaphthalene (CASRN 91-57-6) is a polycyclic aromatic hydrocarbon (PAH),
consisting of two-fused aromatic rings with a methyl group attached on one of the rings at the number
two carbon (Figure 1). Synonyms include $-methylnaphthalene. Certain physical and chemical
properties are shown below (ATSDR, 1995; CRC, 1990).
Figure 1: 2-Methylnaphthalene
3
CH 3
Chemical Formula: C 11H 10
Molecular Weight: 142.20 g/mol
Melting Point: 34.6 °C
Boiling Point: 241 °C
Density: 1.0058 g/mL (at 20 °C)
Water Solubility: 24.6 mg/L (at 25 °C)
Log K ow: 3.86
Log K oc: 3.39
Vapor Pressure: 0.068 mmHg at 20 °C
Henry's Law Constant: 4.99x10 -4 atm-m 3 /mol
2-Methylnaphthalene is a natural component of crude oil and coal, and is found in pyrolysis and
combustion products such as cigarette and wood smoke, emissions from combustion engines, asphalt,
coal tar residues, and used oils (ATSDR, 1995; HSDB, 2002; Warshawsky, 2001).
Methylnaphthalene (CASRN 1321-94-4) refers to a mixture of approximately two-thirds 2-methyl-
naphthalene and one-third 1-methylnaphthalene (CASRN 90-12-0). Methylnaphthalene is
manufactured from coal tar through the extraction of heteroaromatics and phenols. Distillation of
methylnaphthalene removes 1-methylnaphthalene, leaving 2-methylnaphthalene. Mixtures containing
2-methylnaphthalene are used in the formulation of alkyl-naphthalenesulfonates (used for detergents and
textile wetting agents), chlorinated naphthalenes, and hydronaphthalenes (used as solvents). Pure