Pulse radiolysis of aqueous solutions of nitric oxide at neutral p H shows that the reaction initiated by the hydrated electron, e-(aq), proceeds via NO-and,a new transient thought to be (N,O,)-, and not HWO as indicated previously by steady state radiolysis.Canadian Journal of Chemistry, 48, 393 (1970) Earlier studies (1-31, on the radiation chemistry of nitric oxide solutions indicated that the products of y radiolysis, HNO, and N,O, were explicable by a fairly simple mecl-ranism(4 1 HNO i-%NO + tiNB2 t NiC While the above reaction sequence is stoichisnxtricaiiy correct the pulse radiolysis results demoi~strate that the detailed mechanism is more complex at neutral p%%, particularly with respect to reactions involvil~g anionic species generated via eV(aq).Figure 1 (open circ?esj, shows the trallsie~lt spectrum with absorption maxima at 250 and 380 my, observed from 1.7 mM NO solutio~~s 120 ps after a 2--3 krads, 0.5 ys pulse of electrons from a 2 MeV Van de GraafS accelerator. The spectrum 2 ys after the pulse appears identical and is about 20% lower in intensity at 380 mp. Addition of OH radical scavengers, 10-' M methanol or 2 x 10-% KRSCN, did not remove the transient. The absorption is not observed in 1.7 m M NO solutions containing 0.4 11.1 H2S04 as electron scavenger. Similarly, it is reduced by a factor of about 10 in solutions containing a 20-fold excess of N 2 0 , indicating that a precursor of this species is e-(aq).The permanent product absorption (closed circles) is due to the formation of nitrite (reaction [3]), which absorbs intensely at 210 mp (4). For personal use only.
Efects of Electron DonorsIt is known that hydrogen bonding of alcohol and water with electron-donors increases the lifetime of the -OH proton in the molecule. The phenomenon has been used in the detection of spin-spin multiplets in methanol containing acetone (8). Chapman and King (9) have used dimethyl sulfoxide as a solvent for the classification of alcohols in n.m.r. studies. Table 2 gives the effects of different electron-donors in decreasing values of l/z. The data show that of the three electron-donors used, the ability to depress l/z increases in the order acetone, tetrahydrofuran, and dimethyl sulfoxide. This order is the same as the order of increasing electron-donor strength. Thus, for the reaction OH, .D + D = OH,.D,, the equilibrium constants in mole fraction units are 0.9 (36" in cyclohexane (lo)), 1.4 (35" in cyclohexane (lo)), and 2.9 (35" in CC14 (1 1)) for D = acetone, tetrahydrofuran, and dimethyl sulfoxide, respectively.
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