Allene, polymerization

A very special case among optically active dienes is given by chiral allenes. Polymerization of (-)-(R)-2,3-pentadiene by organometallic transition metal derivatives [59] gives an optically active crystalline polymer to which the structure reported in Table XVI has been assigned. In fact that structure is the only linear structure not possessing symmetry planes or mirror glide planes. 

White crystals m.p. 162-164 C. ll can be prepared by the fermentation of sugar with the mould Aspergillus lerreus or by healing citra-conic anhydride with water at ISO C. Electrolysis of the potassium salt in solution gives allene. Itaconic acid is used as a comonomer in plastics its esters are polymerized to lubricating oils and plasticizers. 

Zigmond, 1988). The ATP-hydrolysis that accompanies actin polymerization, ATP —> ADP + Pj, and the subsequent release of the cleaved phosphate (Pj) are believed to act as a clock (Pollard et ah, 1992 Allen et ah, 1996), altering in a time-dependent manner the mechanical properties of the filament and its propensity to depolymerize. Molecular dynamics simulations suggested a so-called back door mechanism for the hydrolysis reaction ATP ADP - - Pj in which ATP enters the actin from one side, ADP leaves from the same side, but Pj leaves from the opposite side, the back door (Wriggers and Schulten, 1997b). This hypothesis can explain the effect of the toxin phalloidin which blocks the exit of the putative back door pathway and, thereby, delays Pi release as observed experimentally (Dancker and Hess, 1990). 

Ojj 1.5204, in 52% yield. There was a viscous residue of about 1 g, probably resulting from polymerization of the allenic aldehyde (note 2). Redistillation gave about the same amount of residue. 

Concentration in a water-pump vacuum gave the chloroallene, n 1.5980, in more than 90% yield. The NMR spectrum showed that no starting compound was present and the purity was satisfactory. Attempts to distil the allene led to extensive polymerization. 

The polymerization filling was effected by the ion-coordination mechanism [17-19]. The monomers were ethylene, propylene, allene, os-butylene, butadiene. The fillers were mineral materials such as ash, graphite, silica gel, glass fibers. The ultimate aim of filler conditioning prior to polymerization is to secure, on its surface, metal complex or organometallic catalysts by either physical or chemical methods [17-19],... 

Polymerization thermodynamics has been reviewed by Allen and Patrick,323 lvin,JM [vin and Busfield,325 Sawada326 and Busfield/27 In most radical polymerizations, the propagation steps are facile (kp typically > 102 M 1 s l -Section 4.5.2) and highly exothermic. Heats of polymerization (A//,) for addition polymerizations may be measured by analyzing the equilibrium between monomer and polymer or from calorimetric data using standard thermochemical techniques. Data for polymerization of some common monomers are collected in Table 4.10. Entropy of polymerization ( SP) data are more scarce. The scatter in experimental numbers for AHp obtained by different methods appears quite large and direct comparisons are often complicated by effects of the physical state of the monomei-and polymers (i.e whether for solid, liquid or solution, degree of crystallinity of the polymer). 

Allen, P.E.M. Patrick, C.R. Kinetics and Mechanisms of Polymerization Reactions Ellis Horwood Chichester, 1974. 

P. E. Allen and C. R. Patrick, Kinetics and Mechanism of Polymerization Reactions , Ellis Horwood, Chichester, 1974. 

The polymerization of allenes by [Rh(CO)2Cl]2 and a ligand (phosphines, arsines, amines, isocyanides) (175) and the polymerization of cyclohexyl isocyanide by Co2(CO)g (173) have been reported. 

Allen, P. E. M Patrick, C. R., "Kinetics and Mechanisms of Polymerization Reactions", John Wiley Sons, (1974)... 

Osakada, K. and Takeuchi, D. Coordination Polymerization of Dienes, Allenes, and Methyl-enecydoalkanes. Vol. 171, pp. 137-194. 

The quantitative aspects of track reactions are involved some details will be presented in Chapter 7. The LET effect is known for H2 and H202 yields in aqueous radiation chemistry. The yields of secondary reactions that depend on either the molecular or the radical yield are affected similarly. Thus, the yield of Fe3+ ion in the Fricke dosimeter system and the initiation yield of radiation-induced polymerization decrease with LET. Numerous examples of LET effects are known in radiation chemistry (Allen, 1961 Falconer and Burton, 1963 Burns and Barker, 1965) and in radiation biology (Lamerton, 1963). 

Analogously, the trienynoate 92 reacted in a 1,10-addition to give the 3,5,7,8-tetra-enoate 93 and the even higher unsaturated allene 95 was obtained from the Michael acceptor 94 containing four double bonds between the triple bond and the acceptor substituent (Scheme 2.33). In the latter case, however, the yield was only 26% this is presumably due to the reduced thermal stability of the starting material and/or the addition product (the 1,12-adduct 95 was the only isolable reaction product, apart from polymeric compounds) [57]. 

Synthetic applications of carbon radical additions to allenes cover aspects of polymerization, selective 1 1 adduct formation and homolytic substitutions. If heated in the presence of, e.g., di-tert-butyl peroxide (DTBP), homopolymerization of phenylal-lene is observed to provide products with an average molecular weight of 2000 (not shown) [58]. IR and 1H NMR spectroscopic analyses of such macromolecules point to the preferential carbon radical addition to CY and hence selective polymerization across the 2,3-double bond of the cumulene. Since one of the olefinic jr-bonds from the monomer is retained, the polymer consists of styrene-like subunits and may be... 

The rearrangement of arylethynyl carbinols 58 that occurs via allene intermediates 59 and 60 in the presence of a polymeric silylvanadate catalyst37 (equation 23) is noteworthy. 

Wyman, Allen and Altares (20) reported that the carbonation of poly-(styryl)lithium in benzene with gaseous carbon dioxide produced only a 60% yield of carboxylic acid the acid was contaminated with significant amounts of the corresponding ketone (dimer) and tertiary alcohol (trimer) as shown in eq. 6. A recent, careful, detailed investigation of the carbonation of polymeric organolithium compounds has... 

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