Decomposition of the 1,3-butadiene radical cation on the microsecond to picosecond time scale

Abstract

1972). (17) N. M. M. Nibbering has informed us of a very slow reaction to eliminate CH40 for Ionized P-bvtene and methyl vinyl ether. We were unable to detect this reaction. Abstract:The decomposition of ionized 1,3-butadiene to give C3H3+ and .CH3 has been studied over the time interval of approximately 10-11-10-5 s using the complementary techniques of field ionization kinetics (FIK) and mass-analyzed ion kinetic energy spectroscopy (MIKES). By employing both carbon-1 3 and deuterium labeled 1,3-butadiene, it has been established that (1) hydrogen atom randomization takes place very rapidly and is complete by approximately lo-" s, (2) carbon atom randomization occurs at a slower rate which is competitive with the decomposition reaction. The hydrogen atom randomization is postulated to take place by isomerization to other acyclic C4H6 ions without change in the carbon skeleton. The near lack of carbon atom interchange at short times (10-9-10-11 s) is explained by invoking a high-energy formation of a methylcyclopropene which occurs as a rate-determining step. For more slowly decomposing (metastable) C4H6 ions, the ring-opening reaction of this intermediate to re-form the 1,3-butadiene cation becomes more competitive with dissociation, and this explains the nearly complete carbon atom randomization at longer times.

Coupling of chemical oscillators

“…No significant change was observed, so this extra complexity was abandoned. "Constant constraints; [BrO3-]0 = [MA]0 = 3 X "2 M, [Ce3+]0 = 3 X.ltT3 , [H+]" = 1.5 M, k0 = 3.92 X 10~3 s'1, [Br]"(l) = 2 X 10"5 M, [Br']0 = 3 X 10"6 M. 6 SSIII starts at kx = 0 and has, therefore, four positive eigenvalues up to the turning point where the number of positive eigenvalues changes to three, and we go over to SSIV. "SSVII goes to kx = °°and has, therefore, two positive eigenvalues all the way.…”

“…(4) k2 = 2 X 109 M"2 s"1 L•2 = 5 X "5 M"1 s"1 HOBr + Br" + H+ <=> Br2 + H20 (5) BrOf + HBrOj + H+ <=t 2Br02• + H20 (6) k4= IX 104 M"2 s"1 I., = 2 X 107 M'1 s"1 Ce3+ + Br02• + H+ ^Ce4+ + HBr02 (7) k¡ = 6.5 X 10s M"2 s"1 k_s = 2.4 X 107 M"1 s"1 Ce4+ + Br02• + H20 ^Ce3+ + BrOf + 2H+ Each of these groups has measured several component steps of the mechanism. Also a different estimate is given for the dissociation constant of bromous acid which bears on the estimate of some rate constants.…”

The C4H6•+Potential Energy Surface. 2. The Reaction of Ethylene Radical Cation with Acetylene

“…The absence of photodissociation products from BTY and DA, reported by Preuninger and Farrar, was explained later by Bunn and Baer , and by Russell et al , …”

Four decades of joy in mass spectrometry

“…That hydrogen atoms can migrate very fast over a carbon skeleton was shown in cooperation with Professor M.L. Gross by a deuterium labeling study of 1,3‐butadiene where from the loss of a methyl radical from its molecular ion it was found that the hydrogen randomization was complete at molecular ion lifetimes of ∼10 −11 sec (Russell et al, 1979b). This methyl radical contained more than 85% of the terminal carbon atoms at molecular ion lifetimes of ∼10 −11 sec as shown by 13 C labeling, but at longer ion lifetimes the inner carbon atoms also participated increasingly, though slowly, in this methyl loss which became almost random at 10 −5 sec.…”