Electron transfer from carbanionic salts to linear sequences of conjugated double bonds, 1. Mechanism of n doping of polyacetylene

Abstract

It is shown that the mechanism of polyacetylene (PA) reduction (or n "doping") by alkaline carbanionic salts and butyllithium is a simple electron transfer without addition. In this reduction reaction the dicarbanionic dimer of 1 ,I-diphenylethylene (DD2-N%+ ) is quantitatively converted to 1,1 -diphenylethylene. The reduction by 3-methyl-1, 1 -diphenylpentyllithium produces free radicals which deactivate in solution by coupling and disproportionation. But the strong dependence of the ratio of disproportionation to coupling of these radicals on solvent polarity is unusual: no coupling is observed in diethyl ether or pentane, while it is the most important reaction in THF. sec-Butyllithium in pentane also reduces PA by a simple electron transfer process. The "doping" levels can be deduced accurately from the quantitive analysis of the by-products by gas chromatography. R -An electron is transferred from the carbanion to PA with formation of a free radical which reacts rapidly in solution leading to by-products. Several points concerning this process have to be examined:-Are there any secondary reactions such as direct addition of carbanions to double bonds, metalation of PA by H exchange, or reaction between polymer and free radicals? (Such reactions may shorten the length of conjugated double bond sequences).

Grafting of Anionic Polymers onto C60 in Polar and Nonpolar Solvents

“…If some diadduct PS 2 C 60 is present, the major product contains no C 60 and must result from coupling of two parent PS chains. The presence of coupled chains (PS−PS) can be explained if one takes into account the fact that, in polar solvents, carbanions are able not only to add to double bonds but also to transfer electrons to conjugated molecules. , If such an electron transfer occurs from the PS - K + to the highly electroaccepting C 60 , the carbanionic PS converts to a radical, and it is well-known that the main reaction of these very reactive polystyryl radicals is recombination . The third compound corresponds mainly to unreacted PS coming from the excess of “living” PS used.…”