The torsional frequencies have been rigorously evalulated in the compo
unds 1:2,4, 5-tetrachloro-3,6-dinitrobenzene and 1,3,5-trichloro-2,4-d
initrobenzene over an extended temperature range (77 K-392 K) using th
e experimental results of NQR and crystal structure data. The values h
ave been compared with those obtained by using the X-ray thermal param
eters.