IUPAC Name: 6-chlorobenzo[a]pyrene 
Empirical Formula: C₂₀H₁₁Cl
Molecular Weight: 286.7543g/mol 
Structure of  6-Chlorobenzeno(a)pyrene (CAS NO.21248-01-1):

Index of Refraction: 1.879
Molar Refractivity: 95.2 cm³
Molar Volume: 208 cm³
Polarizability: 37.74×10^-24cm³
Surface Tension: 64.4 dyne/cm
Density: 1.378 g/cm³
Flash Point: 243.7 °C
Enthalpy of Vaporization: 73.35 kJ/mol
Boiling Point: 495 °C at 760 mmHg
Vapour Pressure: 1.87E-09 mmHg at 25°C 
Classification Code: Tumor data 
Canonical SMILES: C1=CC=C2C(=C1)C3=C4C(=C2Cl)C=CC5=CC=CC(=C54)C=C3
InChI: InChI=1S/C20H11Cl/c21-20-16-7-2-1-6-14(16)15-10-8-12-4-3-5-13-9-11-17(20)19(15)18(12)13/h1-11H
InChIKey: YBIBTKJSLUJSSJ-UHFFFAOYSA-N

Questionable carcinogen with experimental tumorigenic data. When heated to decomposition it emits toxic fumes of Cl⁻. See also CHLORINATED HYDROCARBONS, AROMATIC; and PYRENE.

  6-Chlorobenzeno(a)pyrene , its cas register number is 21248-01-1. It also can be called 3-05-00-02520 (Beilstein Handbook Reference) ; 6-Chlorobenzo(a)pyrene ; BRN 2464084 . When heated to decomposition it emits toxic fumes of Cl⁻. And the storage environment of  6-Chlorobenzeno(a)pyrene (CAS NO.21248-01-1) should be ventilate, low-temperature and dry.