Origin of Impurities Formed in the Polyurethane Production Chain. 1. Conditions for Chlorine Transfer from an Aryl Isocyanide Dichloride Byproduct

Phenyl and 4-methylphenyl isocyanide dichlorides are models for byproduct that may be formed in the later stages of certain polyurethane production chains. Photochemical electron paramagnetic resonance (EPR) studies (λ > 310 nm), using the spin trap, <i>N</i>-<i>tert</i>-butyl-α-phenylnitrone, confirm a previously made suggestion that ArNCCl₂ can behave as a chlorine radical source. EPR spectra recorded during and after irradiation and supported by simulations evolve over time and indicate formation of the short-lived spin trap–Cl^• adduct and a longer lived benzoyl-<i>N</i>-<i>tert</i>-butylnitroxide radical. Photolysis of C₆H₅NCCl₂, either alone or mixed with methylene diaryl isocyanate species, in <i>o</i>-C₆H₄Cl₂, a polyurethane process solvent, led to the formation of mixtures containing dichloro- and trichlorobiphenyl isomers