Phenyl vinyl ketone, polymerization

Both UV- and y-irradiation have been applied successfully for the initiation of methyl isopropenyl ketone [349-351] and phenyl vinyl ketone polymerization [341]. Since polymerization initiated by y-irradiation was inhibited by chinone, a radical mechanism was proposed. 

With the CMR, phenyl vinyl ketone was prepared by passage of a 5% aqueous slurry of N-(2-benzoylethyl)-N,N,N-trimethylammonium iodide through the micro-wave zone. The product was immediately extracted from the cooled aqueous effluent into chilled Et20, avoiding polymerization of the monomer and giving near quantitative yields [22],... 

The decrease of the first wave of phenyl vinyl ketone with time was used for the evaluation of the rate constant. Since hydroxide ions were always present in excess, it was possible to compute the rate constants at a given concentration according to a first-order rate equation. Rate constants obtained in this way were found to be proportional to hydroxide concentration, giving no indication of a reaction with the solvent or general base catalysis. The cleavage of phenyl vinyl ketone in alkaline media is thus first order in ketone and first order in hydroxide ion. The occurrence of dimerization and polymerization in the rate-determining step was therefore excluded. The simplest reaction scheme is given in (14) ... 

Contrary to acrylic esters or acrylonitrile, a vinyl ketone could be polymerized with aluminum (or zinc) alkyl alone in the absence of any added Lewis bases. The mechanism of polymerization of phenyl vinyl ketone(PVK) was studied by using a model initiator, ethylzinc-1,3-diphenyl-l-pentene-l-olate (ZC), which possessed the same structure (see below) as the growing chain end in zinc alkyl-initiated polymerization of PVK (12). 

Feng [344] has described the dibenzoyl peroxide-initiated polymerization of t-butyl vinyl ketone to an amorphous polymer in organic solvents, while several alkyl vinyl ketones have been polymerized in aqueous solutions to low-melting polymers using a potassium persulfate/sodium metabisulfite initiation [345]. Phenyl vinyl ketone was polymerized in an emulsion containing 7.5% soap and 0.2% potassium peroxodisulfate [346]. 

The lithium-initiated polymerization of phenyl vinyl ketone was carried out in bulk and in tetrahydrofuran at room temperature [341] and in liquid ammonia at — 78 °C [346]. No difference in the reactivity of sodium and lithium toward this monomer was recognized. 

Attempts to add acrolein to aetivated olefins led to polymerization, but methaerolein, crotonaldehyde and cinnamaldehyde reaet normally with acrylates and aerylonitrile (Scheme 1.46). ° Upon treatment of these a,jS-unsaturated aldehydes with methyl vinyl ketone in the presenee of DABCO, the self-eondensation product 3-methylenehepta-2,6-dione was obtained exclusively some MBH adduct was isolated with phosphine catalysis (Scheme 1.46). In addition, crotonaldehyde does not add to phenyl vinyl sulfone. ... 

PTAD reacts spontaneously with vinyl ethers to give 1,4-dipoles (478) which are able to react with weakly dipolarophilic alkyl ketones to form (479), together with a polymeric material <7lJOC2838, 83JOC822>. A similar reaction takes place when 1-phenyl-4-vinylpyrazole is treated with PTAD at —60°C in acetone (Scheme 102) <85TL6357>. 

In some cases, products of reactions of TADs are best explained by the existence of 1,4-dipolar intermediates, and sometimes such intermediates have been observed. Some examples of [2 + 2] cycloaddition and ene reactions have been treated with the respective Sections IV,B and IV,C. There are many other types of reactions where such intermediates have been suggested and/or proved. For example, vinylethers 304 give with PTAD mixtures of 1,2-addition and polymeric products, the formation of which can be easily explained by 1,4-dipolar intermediates 305 (72JOC1454). In the presence of alkyl ketones, e.g., acetone, PTAD reacts spontaneously with vinyl ethers via these 1,4-dipoles 305, which are able to add to weakly dipolarophilic acetone to form 306, together with a polymeric material (71JOC2838 83JOC822). A similar reaction takes place when 1-phenyl-4-vinylpyrazole (307) is treated with PTAD at -60°C in acetone (85TL6357). 

Much of the work in this area has focussed on polymeric dyes which can participate in redox reactions. Early work by Manecke and Kossmehl on vinyl Malachite Green (VMG) is specially significant as it established a simple method of entry into the polymerizable triphenylmethane class of dyes. Thus the carbinol base form (ill) of VMG was synthesized by a Grignard reaction between vinyl-phenyl magnesium chloride (l) and Michler s ketone (ll). 

---