Structural studies of radical reaction products. I. The structure of an asymmetrically substituted diazene: 3-(p-chlorophenyl)-4-(p-chlorophenylazo)-4-methyl-2-pentanone, C18H18Cl2N2O

The title compd., from the decompn. of 4-chlorobenzenediazonium chloride by Ti ions in the presence of 4-methyl-3penten-2-one, is triclinic, space group P‾1, with a 15.863(7), b 10.226(4), c 5.765(4) Å, α 92.30(8), β 88.37(8), and γ 108.70(9)°; d.(exptl.) = 1.30 and d.(calcd.) = 1.31 for Z = 2. Final R 0.0415 for 2176 obsd. reflections [having I ≥ 3σ(I)]. At. parameters are given. The distance between the N atoms of the azo group (1.240(3) Å) is equal to the expected bond length between doubly bonded sp2-hybridized N atoms, and there is no evidence of π delocalization between the azo group and the Ph rings. This structure proves unambiguously that aryl radical addn. to a sterically hindered olefin is governed by steric factors