Naphthalene sodium initiator

One-electron reduction of unsaturated a,8-diketones may sometimes generate a diene structure and initiate condensation. Thus, triazoledions (TAD) pass into tetraazabicyclooctanetetraones (TABO). Naphthalene-sodium (ca. 1 mol%), sodium metal, or even sodium iodide efficiently catalyzes the reaction. Tetracyanoethyene and lead tetraacetate retard it. Consequently, the condensation has a chain character (Borhani and Greene 1986 Scheme 7.30). 

Another way to initiate anionic polymerization is by electron transfer. The reaction of sodium with naphthalene gives sodium naphthalene (sodium dihydro-naphthylide) in which the sodium has not replaced a hydrogen atom, but has transferred an electron to the electronic levels of the naphthalene this electron can be transferred to styrene or a-methylstyrene, forming a radical anion ... 

Eor comparison, polystyrene and poly(4-vinylpyridine) are prepared by anionic polymerization with sodium naphthalene as initiator. Poly(4-vinylpyridine) precipitates from THE the mixture is poured into 200 ml of diethyl ether and the polymer filtered off.The polymer is then reprecipitated from pyridine solution into a ten-fold amount of diethyl ether and dried in vacuum. 

Electron transfer from polycyclic aromatic radical anions in polar solvents can also initiate propagation.120 168 169173 One of the early and best understood systems is naphthalene-sodium, a green solution of stable, solvated naphthalene radical anion.176 177 The electron transfer from the radical anion to the monomer yields a new radical anion [Eq. (13.33)]. The dominant reaction of the latter is its head-to-head dimerization to the stabile dimeric dicarbanion [Eq. (13.34)], which is the driving force for the electron transfer even when electron affinity of the monomer is less than that of the polycyclic molecule. Propagation proceeds at both ends of the chain ... 

Compounds such as sodium naphthalene can initiate polymerization by mechanisms involving addition. This is known to occur for ethylene oxide [95], viz. 

Alkali metal naphthalene complexes have also been used to initiate epoxide polymerizations. Solov yanov and Kazanski [25] studied the polymerization of EO in tetrahydrofuran using sodium, potassium or cesium naphthalene as initiator. A living polymer was produced there is no chain rupture or transfer. The rate of polymerization depends on the concentration of active centres in a complex manner. The kinetic order varies from 0.23 for Na" (or 0.33 for K and Cs" ) up to full first order as initiator concentration decreases. The polymerization is first order in monomer, but deviations are observed at high concentrations. 

In model studies of the naphthalene-sodium-tetrahydro-furan system, tetrahydrofuran was found to decompose to ethylene and the sodium enolate of acetaldehyde, with the ethylene alkylating the naphthalene in both reductive and nonreductive modes. The initial step of this decomposition, proton abstraction from the alpha carbon of tetrahydrofuran, led to formation of a hydride of unknown form. 

For the synthesis of the (PI)3PS(PI)3 super-H copolymers,161 a difunctional PS chain, derived from the polymerization of isoprene in THF using sodium naphthalene as initiator, was reacted with a large excess of SiCL, giving a PS chain with three Si—Cl active bonds at each end. After elimination of excess SiCL and the addition of excess PILi living arms, the (PI)3PS(PI)3 super-H shaped copolymer was isolated (Scheme 74). Using the same synthetic strategy, (PS—PI)3PS(PI—PS)3 block copolymers were also synthesized.162... 

The apparent propagation rate constant for polymerization of styrene in THF at 25°C using sodium naphthalene as initiator is 550 L mol s . If the initial concentration of styrene is 156 g/L and that of sodium naphthalene is 0.03 g/L, calculate the initial rate of polymerization and, for complete conversion of the styrene, the number average molecular weight of the polystyrene formed. Comment upon the expected value of the polydispersity index (M /M ) and the stereoregularity of the polystyrene produced. 

At present, we do not believe that Na metal in the films is responsible for initiation since n-type (CH)X films which contained a 2 1 naphthalene/sodium ratio were still highly active as polymerization initiators. A comparison of the number of (CH)X carbanions which are initiators with the number, if any, of electron transfer sites may yield important information about the distribution of charge carrier reactivities in doped (CH)X. 

One of the first living polymer systems studied was the polymerization of styrene initiated by sodium naphthalene. The initiator is formed by adding sodium to a solution of naphthalene in an inert solvent, tetrahydrofuran. 

Radicals may also result from chemical or electrochemical oxidation or reduction of stable molecules. Single-electron transfer processes initially generate radical cations (for oxidation) or radical anions (for reduction), which may then fragment to radicals and ions. For example, Sargent and coworkers determined that in 1,2-dimethoxyethane solutions the radical anion of naphthalene (sodium naph-thalenide, Na" " Ar ) transferred an electron to propyl iodide. Subsequent loss of... 

Linear pentablock terpolymers PBLL-Z -PBLG-Z -PS-Z -PBLG-Z -PBLL (BLL r -butylox-ycarbonyl-L-lysine, PS polystyrene) were recently synthesized by Karatzas et al. (2008) using a,co-diamino-PS. This polymer was prepared by anionic polymerization of styrene with sodium/naphthalene (difunctional initiator) and termination with l-(3-bromo-propyl)-2,2,5,5-tetramethyl-aza-2,5-disilacyclopentane, and of deprotection by successive... 

The kinetics of polymerization of EO have also been investigated in pure ethereal solvents. In THE ( =7.6, 25 °C) in the presence of sodium, potassium, and cesium naphthalene as initiators, a living polymerization takes place, ° the rate of propagation increasing with the size of the counterion. The kinetics are however complicated by strong association of alkoxide end groups manifesting itself by the low fractional kinetic order of the reactants, that is, 0.25 for Na alkoxide and 0.33 for K and Cs salts. ° Dissociation constants are very low (see Table 1). 

Aromatic radical anions, such as lithium naphthalene or sodium naphthalene, are efficient difunctional initiators (eqs. 6,7) (3,20,64). However, the necessity of using polar solvents for their formation and use limits their utility for diene polymerization, since the unique abiUty of lithium to provide high 1,4-polydiene microstmcture is lost in polar media (1,33,34,57,63,64). Consequentiy, a significant research challenge has been to discover a hydrocarbon-soluble dilithium initiator which would initiate the polymerization of styrene and diene monomers to form monomodal a, CO-dianionic polymers at rates which are faster or comparable to the rates of polymerization, ie, to form narrow molecular weight distribution polymers (61,65,66). 

Polymerization of ethylene oxide might be initiated by electron transfer process if metallic Na or Li is used as an initiator. On the other hand, initiation by sodium naphthalene involves not electron transfer but addition to naphthalene- ion. 

An interesting initiator is the naphthalene radical-anion formed by electron-transfer from sodium to naphthalene... 

The precipitated silica (J. Crosfield Sons) was heated in vacuo at 120° for 24h. before use. Two grades of surface areas 186 and 227 m g l (BET,N2), were used during this project. Random copolymers, poly(methyl methacrylates) and polystyrene PS I were prepared by radical polymerization block polymers and the other polystyrenes were made by anionic polymerization with either sodium naphthalene or sodium a methylstyrene tetramer as initiator. The polymer compositions and molecular weights are given in Table I. 

In place of phenyl lithium, if we use sodium naphthalene as the initiator, then the chains may grow in both the direction and... 

Some alkali metal complexes are also capable of initiating anionic polymerisation. For example, sodium and naphthalene in tetrahydrofuran is a homogeneous solution initiates polymerisation as follows ... 

The primary starting material for the synthesis of perylene tetracarboxylic acid pigments is the dianhydride 71. It is prepared by fusing 1,8-naphthalene dicar-boxylic acid imide (naphthalic acid imide 69) with caustic alkali, for instance in sodium hydroxide/potassium hydroxide/sodium acetate at 190 to 220°C, followed by air oxidation of the molten reaction mixture or of the aqueous hydrolysate. The reaction initially affords the bisimide (peryldiimide) 70, which is subsequently hydrolyzed with concentrated sulfuric acid at 220°C to form the dianhydride ... 

Reduction of poly(butyl)naphthalenes with sodium-potassium alloy in ether causes their isomerization (Goldberg et al. 1976). The reduction of l,3,6,8-tetra(tcrt-butyl)naphthalene produces an anion-radical, which disproportionates yielding the initial tetrabutylnaphthalene and corresponding dianion (Scheme 6.32). 

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