NITROUS ACID DECOMPOSITION CATALYZED BY AN IRON(II) COMPLEX: TRIS(3,4,7,8-TETRAMETHYL-1,10-PHENANTHROLINE)IRON(II)1.

Article abstract of DOI:10.1021/ja00367a013

In the presence of low concentrations of tris(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II) (Fe**I**ITMP), nitrous acid decomposes to yield nitric oxide and nitrate. The kinetics of this two-stage reaction have been studied by using rapid-mixing techniques. During the first rapid phase, Fe**I**ITMP is oxidized by HNO//2 and by NO//2** minus to Fe**I**I**ITMP. The initial ferrous complex is then regenerated in a slower second phase dominated by the reaction of Fe**I**I**ITMP with NO//2. Rate constants for the reactions of Fe**I**I**ITMP with nitrous acid and with nitrite were found to be (7. 26 plus or minus 0. 07) multiplied by 10**2 M** minus **1 s** minus **1 and (2. 5 plus or minus 0. 03) multiplied by 10**4 M** minus **1 s** minus **1, respectively, at 25 degree C and ionic strength 0. 5 M. Computer simulations have been carried out by using a mechanism developed for the hexaaquoiron(II)-nitric acid system, with appropriate modification for the different kinetic properties of the iron species.