Pulse radiolysis of nitric oxide in aqueous solution

Abstract

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.

Pulse Radiolysis of Nitric Oxide in Aqueous Solution

“…It should be noted here that we find the rate of decay of N303-to be temperature dependent. This feature will be discussed in more detail later but does explain the large discrepancy in rate constants previously reported for this process (4,5). The overall kinetics and yields of NO-, N 2 0 2 -, and N 3 0 3 -are dependent both on NO concentration and pH.…”

“…The complete On a is given here. A Van de Graaff accelerator operating at pS time scale, is due to the formation of N 2 0 2 -2.25 MeV with pulse lengths 0.5-2 ps was used as the (4), while the additional slow build up requiring electron source. Experiments were generally conducted some 250 ps to reach completion is a composite with a 1 ps pulse with currents in the range of 150 mA/ pulse and a dose of about 3 krads.…”

“…Earlier studies (1)(2)(3), on the y radiolysis of nitric oxide in aqueous solutions showed that the major products, HNO, and N,O, were explicable by a simple mechanism: study (4) indicated the detailed mechanism to be much more complex involving the anionic species NO-and N,O,-and their corresponding protonated forms HNO and HN,O,. Subsequent st~tdies (5) confirmed the existence of NO-and N,O,-together with the formation and eventual decay of a third polymeric anion N,O,-.…”

The Specificity of Nitroxyl Chemistry Is Unique Among Nitrogen Oxides in Biological Systems

“…Conversion of HNO to NO either by simple oxidation or by reductive nitrosylation can lead to formation of reactive intermediates (Eqs. 13-15) (57,142,143,145).…”

Biochemistry of Nitric Oxide

“…It reacts with two nitric oxides to form nitrite and nitrous acid [14,15]. The reaction intermediate (ONNO -) is quite similar to peroxynitrite.…”