An electron spin resonance study of the radiolysis of aqueous solutions of cyanate ion

The in situ radiolysis-esr method has been used to investigate the radicals produced in aqueous solutions of cyanate ion (NCO^-) by high-energy electron irradiation. Over the pH range 3.6-12.4, N₂O-saturated solutions give rise to a proton-containing radical with the esr parameters a^N = 13.73, a^H = 10.87 G, and g = 2.00425. From the dependence of the intensity of this spectrum upon flow rate and the concentration of NCO^- it is concluded that the radical is a primary product and most probably has the structure HNCO₂^-. Over the pH range 6.5-10.5 another radical which contains two nitrogen atoms and has the parameters a^N = 9.82, a^N′ = 5.90, a^H = 7.84, and g = 2.00404 is observed. This radical can best be assigned as ^-O₂CNHNCO₂^- formed by a secondary reaction of OH with the dimer of the primary radical. Above about pH 12 yet another radical is found which also seems to be a secondary product. On the basis of earlier studies this radical can be assigned the structure ^-O₂CNO₂^-. No radicals resulting from the reaction of e_aq^- with cyanate were found. Radicals which may have the structure RO₂CN^- were produced by allowing methyl and ethyl carbamate to react with HOCl and allowing the resultant N-chloro compounds to react with e_aq^- in basic solution. The spectra for the two esters were similar in their gross features with a^N ∼ 11 G and g ∼ 2.0048.