Polymerization of ketones

The polymerization of ketones was studied for theoretical reasons. Acetone has an unusually low ceiling temperature and yileds high-molecular-weight polymers only at low temperatures (ca. 70 K) its polymer depolymerizes at temperatures of about 100 K. 

Synthesis and Properties. Polyquinolines are formed by the step-growth polymerization of o-aminophenyl (aryl) ketone monomers and ketone monomers with alpha hydrogens (mosdy acetophenone derivatives). Both AA—BB and AB-type polyquinolines are known as well as a number of copolymers. Polyquinolines have often been prepared by the Friedlander reaction (88), which involves either an acid- or a base-catalyzed condensation of an (9-amino aromatic aldehyde or ketone with a ketomethylene compound, producing quinoline. Surveys of monomers and their syntheses and properties have beenpubhshed (89—91). 

The wide variety of ketomethylene and amino ketone monomers that could be synthesized, and the abiUty of the quinoline-forming reaction to generate high molar mass polymers under relatively mild conditions, allow the synthesis of a series of polyquinolines with a wide stmctural variety. Thus polyquinolines with a range of chain stiffness from a semirigid chain to rod-like macromolecules have been synthesized. Polyquinolines are most often prepared by solution polymerization of bis(i9-amino aryl ketone) and bis (ketomethylene) monomers, where R = H or C H, in y -cresol with di-y -cresyl phosphate at 135—140°C for a period of 24—48 h (92). 

The procedure described is essentially that of Shioiri and Yamada. Diphenyl phosphorazidate is a useful and versatile reagent in organic synthesis. It has been used for racemlzatlon-free peptide syntheses, thiol ester synthesis, a modified Curtius reaction, an esterification of a-substituted carboxylic acld, formation of diketoplperazines, alkyl azide synthesis, phosphorylation of alcohols and amines,and polymerization of amino acids and peptides. - Furthermore, diphenyl phosphorazidate acts as a nitrene source and as a 1,3-dipole.An example in the ring contraction of cyclic ketones to form cycloalkanecarboxylic acids is presented in the next procedure, this volume. 

Besides a polymerization of the Michael acceptor, a double alkylation of the starting ketone, by reaction with a second Michael acceptor molecule, may take place as a side reaction, and thus further reduce the yield. The polymerization of the enone 2 as well as the double alkylation of the starting ketone can be avoided by application of a modern procedure for the Robinson annulation that uses an organotin triflate as catalyst." ... 

An antipolymerization agent such as hydroquinone may be added to the reaction mixture to inhibit the polymerization of the maleate or fumarate compound under the reaction conditions. This reaction is preferably carried out at a temperature within the range of 20°C to 150°C. This reaction is preferably carried out at atmospheric pressure. Reaction time of 16 to 24 hours have bean specified for this reaction by J.T. Cassaday. The reaction is preferably carried out in a solvent such as the low molecular weight aliphatic monohydric alcohols, ketones, aliphatic esters, aromatic hydrocarbons or trialkyl phosphates. 

Recently, Dutta and Maiti [21] reported nitro displacement polymerization of the bisphenol dianion with the sulfone activated dinitro aromatic compounds. In addition, there have been recent reports of the development of functionalized PEEK [22] and polyether sulfone ketone (PESK) [23] that are comparable to commercially available high performance polymers. 

In contrast with the above situation, the polymerization of 2-furfurylidene methyl ketone, di-2-fiirfurylidene ketone and their homologues has been the subject of a large volume of (mainly technical) publications because of the useful applications of the final cross-linked products. As pointed out in the introduction, this review does not deal with the technological aspects of furan resins and in this section only the mechanistic aspects of the first phase of these polymerizations will be discussed. 

The polymerization of /3-(2-furyl) acrolein and some of its homologues by acids141 gave a similar phenomenology and thus, presumably, the mechanism is similar to that of the corresponding ketones. Their 7-radiation polymerization only proceeded in solution, probably because acidic substances were formed from the solvent142. ... 

ATRP is usually performed in solution. Many solvents can be used with the proviso that they do not interact adversely with the catalyst. Common solvents include ketones (butanonc, acetone) and alcohols (2-propanol). Solvents such as anisole and diphenyl ether are frequently used for polymerizations of S and other less polar monomers to provide greater catalyst solubility. 

Other coupling reactions were also employed to prepare poly(arylene etherjs. Polymerization of bis(aryloxy) monomers was demonstrated to occur in the presence of an Fe(III) chloride catalyst via a cation radical mechanism (Scholl reaction).134 This reaction also involves carbon-carbon bond formation and has been used to prepare soluble poly(ether sulfone)s, poly(ether ketone)s, and aromatic polyethers. 

The striking simplicity of the methacrylate polymerization caused by the introduction of a t-butyl group was noted also in anionic polymerization of related monomers such as t-butyl acrylate57), t-butyl crotonate 58) and t-butyl vinyl ketone. 

Transition-metal-based Lewis acids such as molybdenum and tungsten nitro-syl complexes have been found to be active catalysts [49]. The ruthenium-based catalyst 50 (Figure 3.6) is very effective for cycloadditions with aldehyde- and ketone-bearing dienophiles but is ineffective for a,)S-unsaturated esters [50]. It can be handled without special precautions since it is stable in air, does not require dry solvents and does not cause polymerization of the substrates. Nitromethane was the most convenient organic solvent the reaction can also be carried out in water. 

Ketones are generally not polymerizable, despite claims that acetone can be polymerized at low temperatures (1 ). A simple explanation for the lack of polymerizability of ketones compared to vinyl monomers can be deduced from consideration of Pauling (Z) average bond energies as shown in Equations 1 and 2, where AHP°l(est) is the estimated enthalpy of polymerization based upon the difference in bond energies of the two single bonds formed in the polymer compared to the double bond in the monomer ... 

Activation of Molecular Hydrogen by Homogeneous Catalysts S. W. Weller and G. A. Mills Catalytic Syntheses of Ketones V. I. Komarewsky and J. R. Coley Polymerization of Olefins from Cracked Gases... 

In lipase-catalyzed transesterifications, frequent use of enol esters as acyl agents has been seen [1, 5], since the leaving unsaturated alcohol irreversibly tautomerizes to an aldehyde or a ketone, leading to the desired product in high yields. The polymerization of divinyl adipate and 1,4-butanediol proceeded in the presence of lipase PF at 45 °C [39]. Under similar reaction conditions, adipic acid and diethyl adipate did not afford the polymeric materials, indicating the high polymerizability of bis(enol ester) toward lipase catalyst. 

The lanthanocene initiators also polymerize EtMA, PrMA and BuMA in a well-controlled manner, although syndiotacticity decreases as the bulk of alkyl substituent increases. Reactivity also decreases in the order MMA EtMA > PrMA > BuMA. Chain transfer to provide shorter polymer chains is accomplished by addition of ketones and thiols.460 The alkyl complexes (190) and (191) also rapidly polymerize acrylate monomers at 0°C.461,462 Both initiators deliver monodisperse poly(acrylic esters) (Mw/Mn 1.07). An enolate is again believed to be the active propagating species since the model complex (195) was also shown to initiate the polymerization of MA. 

Most ruthenium-initiated ROMP studies have been performed using (233) and strained cyclo-olefinic monomers such as norbornene688 and cyclobutenes,689 although several reports on the polymerization of 8-membered rings have also appeared.690-692 A wide range of functionalities are tolerated, including ethers, esters, amines, amides, alcohols, carboxylic acids, and ketones. 

Polymerization of a BINAP derivative (Figure 14) followed by complexation with [ RuC12 (benzene) 2] afforded a catalyst showing high enantioselectivities for the hydrogenation of various substrates such as dehydroaminoacids, ketoesters, olefins, and ketones.135 The catalyst may be re-used four times with negligible loss of enantioselectivity and activity. 

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

Scheme 6.79 Hydrosilylation of ketones [164], Dotz benzannulation chemistry [165], cobalt-mediated synthesis of angular [4]phenylenes [166], and nickel-mediated coupling polymerizations [167],...

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],... 

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