Dimeric Dianion Research Articles

Reactions of pyrazine radical anions in solution. I. Study of the kinetics of the dimerization of pyrazine radical anions

The radical anions of pyrazine (pz-.) have been prepared at 294'K by reducing pyrazine (pz) with metallic potassium in 1,2-dimethoxyethane (dme). The resulting reactions of the radical anions are postulat'ed as being described by the equations: The e.s.r, and electronic absorption spectra of all pertinent species were recorded and examined. The kinetics of reaction (1) have been investigated in the dark as well as in light and values of the rate constants have been determined. I n light, reaction (1) did not conform strictly to second-order kinetics and this may be explained by an interaction of pyrazine with dme. The dimer dianion species (-pz-pz-, 2K7) was found to be stable in the dark but decayed slowly in light. This decay was found to exhibit first-order kmetics.

Electron transfer from dimeric dianions of .alpha.-methylstyrene to benzo[e]pyrene

Electron transfer from dimeric dianions of .alpha.-methylstyrene to benzo[e]pyrene

The reaction of anions of diarylketimines with p-toluenesulfonyl azide

The reaction of the chloromagnesium salt of benzophenone imine with tosyl azide gives a mixture of diphenyldiazomethane and of N-tosyl benzophenone imine. Similarly, diazofluorene was formed from the chloromagnesium salt of fluorenone imine and tosyl azide. The lithium salt of benzophenone imine underwent dimerization in solvents such as ether and tetrahydrofuran. The reaction of this dimeric dianion with tosyl azide and with methyl iodide is discussed. Evidence for the structure of the azide formed from dimeric anion and tosyl azide is presented.

The synthesis of cycloalkanes via anionic coupling reactions

A number of cycloalkanes have been isolated among the products of the reactions of geminal and vicinal dihalides with dimeric dianions produced from substituted styrenes by the action of lithium. The n.m.r. and mass spectra of the products are reported.

Kinetic studies of electron-transfers between the mono- and dinegative ions of anthracene and 1,1-diphenyl ethylene

Following the previously described study of the reaction of sodium anthracene, A., with 1,1- diphenyl ethylene, D, giving the sodium salt of the dimeric dianion, -C(Ph) 2 • CH 2 . CH 2 C(Ph) - 2 , nameIy 2A−. + 2D → 2A + − DD − we investigated now the reaction of disodium anthracene, A 2~ with D. It was shown that this extremely fast process produces a mixed dimer ~AD~, which decomposes reversibly into J7 The virtually irreversible dimerization of D7 into ~DD~ leads to complete decomposition of ~AD~ into AT* + ~DD~. The kinetic studies of these processes allowed us to evaluate the relevant rate and equilibrium constants and forced us to reconsider the results of the previous study. The previously proposed mechanism of conversion of A~ + D into A + ~DD~ was found to be correct, namely A* +D A+D* (rapid equilibrium), (i) D ^+ D --> DD• (rate determining step), (2) ~DD- + A~ --> ~DD~ (rapid electron transfer). (3) In addition, side reactions, A^ + A A 2~ + A, (4) A 2~ + D ~AD~, (5) -A D - *± A^+DT (6) form a small amount of the transient mixed dimer ~AD~. This transient was erroneously identified in the previous study as the monomeric radical-ion, and this mistake led to incorrect values of K l9 k2 and I£dig8>> DD~ 2D~, ...(I£di8s.). The corrected results derived from the present studies are K x « 10~7, k2 = 800 1. mole-1 s-1, Jfdi8S> « 10~15 mole/1. The scheme was proved to be self-consistent, and the value K x was confirmed by the potentiometric and equilibrium data.

Chemistry of radical ions: the absolute rate constant of dimerization of radical anions of 1 ,1-diphenyl ethylene

The combination of the labile radical ions, (Ph 2 C:CH 2 )7~, Na+, into dimeric dianions Na + , C - (Ph) 2 .CH 2 .CH 2 .C(Ph) - 2, Na+ was investigated by a flow and a stopflow technique. The bimolecular rate constant of combination was found to be 2 to 3 x 106 1. mole-1 s-1. The reaction was initiated by an electron transfer naphthalene^ + (P/*,2C:CH2) naphthalene+ (P/*,2C:CH^) or terphenylener + (P7fc2C:CH2) ⇔ terphenylene + (Pfe2C:CH^). The equilibrium constant of the first electron transfer process was found to be 20 and of the second about 16. These results are consistent with recent determinations of electron affinities of aromatic hydrocarbons.

Electron‐Transfer Processes in Non‐Aqueous Solutions and Some Intermediate Complexes

AbstractAfter reviewing the earlier work in the field, mainly that of Schlenk and of Ziegler, the principles of electron‐transfer initiation of anionic polymerisation were outlined. It was stressed that three steps need be considered: electron transfer to monomer producing the monomeric radical‐ion, M−, their dimerisation to dimeric‐dianions, i.e., M− + M− → −MM−, and their dimerisation with monomer to dimeric radical‐ions, i.e., M− + M → −MM*.We considered then the various methods which permit us to study quantitatively the two reversible dimerisation processes named above. It was shown that in the system diphenyl ethylene, D, the equilibrium constant of the dissociation process −DD− → D− could be determined by five independent methods all giving consistent results. Moreover, the rate constant of the dissociation of −DD− was determined by two independent methods, and in the course of these studies the rate constant of the association D− + D → −DD→ was calculated.Extension of these investigations to the system α‐methylstyrene — its radical‐ions and dimeric dianions — was also reported.It was stressed that 1:1 complexes are formed between the carbanions and aromatic hydrocarbons. The chemistry of some of these complexes was reviewed and a few unusual observations were reported. The significance of such complexes in electron‐transfer reactions is discussed.