35Cl NQR spectra and crystal structures of 1,2,4,5‐tetrachloro‐3,6‐dinitrobenzene and of 1,3,5‐trichloro‐2,4‐dinitrobenzene

The crystal structures of 1,2,4,5‐Tetrachloro‐3,6‐dinitrobenzene and of 1,3,5‐Trichloro‐2,4‐dinitrobenzene were determined and the temperature dependence of the 35Cl NQR frequencies was investigated. 1,2,4,5‐Cl4‐3,6‐(NO2)2C6 crystallizes monoclinic, space group C32h‐C2/m with 2 molecules in the unit cell. The lattice constants are a = 990.4 pm, b = 923.4 pm, c = 573.5 pm, β = 92.721°. The plane of the nitro groups is perpendicular to the benzene ring. ‐ 1,3,5‐Cl3‐2,4‐(NO2)2C6H crystallizes monoclinic, space group C52h‐P21/c with 4 molecules in the unit cell. The lattice constants are a = 821.3 pm, b = 924.8 pm, c = 1300.0 pm, β = 92.39°. The nitro groups are tilted out of the ring plane (79.7° and 87.6°). — The 35Cl NQR spectra are in agreement with the crystal structures and in both cases no phase transition occurs in the temperature range 77 ≦ T/K ≦ melting point.