Presence Of AIBN Research Articles

Synthesis, study and chemical modification of vinyltetrazole polymers

The authors have studied the radical polymerization of 5-vinyltetrazole and 1-vinyl-5-aminotetrazole. The monomers are readily polymerized by the radical mechanism in presence of AIBN and redox systems. The phenomenon of association and ionization of the monomer and polymer molecules has been found. It has been established that poly-5-vinyltetrazole possesses polarographic activity due to the presence of an acid proton. The thermogravimetric method has established that vinyltetrazole polymers are thermally stable up to 250–260°C after which their heavy degradation is observed. Chemical modification of poly-5-vinyltetrazole has been carried out and some physicochemical properties of the solutions of the initial and modified polymer studied.

Synthesis and polymerization of 4‐o‐vinylbenzyl‐2,2,6,6‐tetramethylpiperidine

AbstractSome hindered amine polymers containing 2,2,6,6‐tetramethylpiperidine structure were synthesized. A new monomer, 4‐O‐vinylbenzyl‐2,2,6,6‐tetramethylpiperidine, was homopolymerized and copolymerized with some vinyl monomers in the presence of AIBN as an initiator. The obtained amine polymers were oxidized with hydrogen peroxide to obtain the polymers having nitroxyl radical moiety.

Cinchona alkaloids for preparing new, easily accessible chiral stationary phases.I. 11-(10,11-Dihydro-6′-methoxy-cinchonan-9-OL)-tiopropylsilanized silica.

By reaction of mercatopropylsilanized silica with quinine in the presence of AIBN as radical initiator, a silica supported alkaloid can be obtained, which is effective in the HPLC resolution of racemic arylalkylcarbinols and binaphtol derivatives.

Copolymerization of N-vinyl-2-pyrrolidone with 2,4,5-trichlorophenyl acrylate and with 2-hydroxyethyl methacrylate : Reactivity ratios and molecular weights

The free radical copolymerization of N-vinyl-2-pyrrolidone ( 1) with 2,4,5-trichlorophenyl acrylate ( 2a) was carried out in chlorobenzene, and in the presence of AIBN, at 50°. Copolymerization of 1 with 2-hydroxyethyl methacrylate ( 2b) was also carried out similarly, except that methanol was employed as a solvent. In either case 7 copolymer samples were obtained by polymerization of mixtures of 1 and 2 (molar ratios 2:8 to 8:2) to about 10% conversion. Compositions of copolymer samples were estimated by micro-analysis (Cl and N), and in the case of copoly ( 1-2b) also by u.v. spectroscopy based on the carbonyl absorption of 1 at 207 nm. Reactivity ratios for 1 2a and 1 2b were computed by the Fineman-Ross method, and were found to be r 1 = 0.01 ± 0.02 and r 2a = 0.16 ± 0.01; and r 1 = 0.06 ± 0.10, r 2b = 4.35 ± 0.04, respectively. Estimation of the reactivity ratios by the Kelen-Tüdős method produced fairly similar values of r 1 = 0.02 ± 0.01, r 2a = 0.17 ± 0.01 and r 1 = 0.02 ± 0.14, r 2b = 4.50 ± 0.24. The molecular weight distributions of copolymers of both systems were examined by GPC. The trends noticed in the results are briefly discussed.

Copoly(m,p-chloromethylstyrene-50% styrene): Copolymer molecular weights, fractionation and derivatization

Abstract Copolymerization of an equimolar mixture of m,p-chloromethylstyrene ( M 1) and styrene ( M 2) was carried out in chlorobenzene in the presence of AIBN at 80°C. Molecular weight analysis (by g.p.c.) of the resulting polymer samples was performed at various conversions. M w , M n , and ( M w M n ) value of 21 300, 13 800 and 1.54 were obtained at 8.9% conversion. At higher conversions, the value of M w remained effectively constant while M n decreased to 9200 at ca. 80% conversion, and then increased to 12 000 at about 100% conversion (16 h), and to 13 700 if the polymer solutions were maintained at 80°C for an additional 44 h. These results suggest that, although the termination step initially involves the combination of polymer radicals, at high conversions a large number of very low molecular weight, and unsaturated, polymer molecules are formed possibly by disproportionation involving polymer radicals and primary radicals. The unsaturated polymer molecules are subsequently polymerized by growing polymer radicals towards the end of the polymerization. It was noticed that further reaction occurred after complete depletion of monomer, involving radical attack on the unsaturated polymer molecules. Other reactions including chain transfer to polymer will also be important at high polymer concentrations. A copolymer of M 1 and M 2 was separated into four fractions on a preparative scale, and molecular weight analysis of the resulting polymer samples provided more evidence of the above interpretation. G.p.c. analysis of several derivatives of a copolymer of M 1 and M 2 showed that most molecular weights were much lower than that of the starting polymer. These results in some cases may reflect the chemical or dimensional changes introduced into the polymer molecules during derivatization.

Synthesis of electroreactive polymers from poly ( m, p-chloromethylstyrene) and copoly ( m, p-chloromethylstyrene-styrene)

Polymerization, and copolymerization with styrene, of m, p-chloromethylstyrene have been carried out at 75°C, in chlorobenzene and in the presence of AIBN ( [ AIBN] ⋍ 6 × 10 −2 , and 12 × 10 −2 m , respectively). The polymer molecular weights, determined by g.p.c., are: M ̄ w = 8670 , M ̄ n = 5860 , and M ̄ w /-M n = 1.48 for the homopolymer, poly( m, p-chloromethylstyrene), ( 1a); and M ̄ w = 8805 , M ̄ n = 5144 , and M ̄ w /-M n = 1.71 for the copolymer, copoly( m, p-chloromethylstyrene-styrene), ( 2a). A series of phosphine derivatives of both 1a and 2a are prepared by the reaction of the polymers with either chlorodiphenylphosphine/lithium, or diphenylphosphine/potassium tert. butoxide. A number of other potentially electroreactive derivatives of 2a are obtained by reacting the polymer with 2-aminoanthraquinone, 3- N-methylamino-propionitrile, or 2-(2-aminoethyl) pyridine. The phosphinated polymers are reacted with bis-benzonitrilepalladium-(II) chloride to obtain a series of polymer-palladium(II) complexes containing 8.5–12.9% palladium. Similarly, reaction of the last-named bidentate polymeric ligand with cupric acetylacetonate, or cupric sulphate pentahydrate, produces polymer-copper(II) complexes having 5.8, or 3.3% copper, respectively. The inter/intra-chain nature of some of the side reactions during the derivatization of the chloromethylated polymers, and that of the complex formation between transition metal centres and macromolecular ligands, are briefly discussed in view of the experimental results.

Effect of the metal atom of acetylacetonates on the autoxidation of cumene

The oxidation of cumene and a cumene-nitrobenzene (1∶2) mixture at 60°C in the presence of AIBN and acetylacetonates of Co(II), Cu(II), Fe(II), Fe(III), V(III), Cr(III), Mn(III) and MoO 2 2+ has been investigated.

Copolymerization of 2‐phenylvinyl alkyl ethers and maleic anhydride

AbstractA series of 2‐phenylvinyl alkyl ethers (I) having as alkyl group methyl, ethyl, n‐propyl, n‐butyl, 2‐methylbutyl, 3‐methylpentyl, and optically active 1‐methylpropyl of (S) absolute configuration, were copolymerized with maleic anhydride to alternating copolymers. The copolymerizations were carried out in bulk at 70°C in the presence of AIBN as initiator. Monomer I (R = Et) was also polymerized with lauroyl and benzoyl peroxide as initiator. The yield and molecular weight were highest when equimolar amounts of both monomers were used. The equilibrium constant of charge‐transfer complex of monomer I (R = Et) and maleic anhydride was determined by the transformed Benessi‐Hildebrand NMR method and has a value of 0.28 mole/1.

Sulphur-containing organometallic compounds: Preparation and some physical properties of ( p-tolylthiomethyl)-triphenyl-tin and -germanium, Ph 3MCH 2SC 6H 4Me- p (M = Ge, Sn) and [2-( p-tolylthio)ethyl]triphenyltin, Ph 3SnCH 2CH 2SC 6H 4Me- p

The preparation and properties of Ph 3MCH 2SC 6H 4Me- p (M = Ge and Sn) and of Ph 3SnCH 2SC 6H 4Me- p are reported. Two synthetic methods have been found for the α-sulphur substituted organometallic compounds; reaction of (1) Ph 3MLi with ClCH 2SC 6H 4Me- p and (2) Ph 3MCH 2X with NaSC 6Me- p (X = I, Cl). For the β-sulphur substituted compounds three routes are possible; reaction of (1) Ph 3SnCHCH 2 with HSC 6H 4Me- p in the presence of AIBN, (2) Ph 3SnH with CH 2CHSC 6H 4Me- p also in the presence of AIBN and (3) (Ph 3Sn) 2Mg+BrCH 2CH 2SC 6H 4Me- p. The Ph 3MCH 2SH 6H 4Me- p compounds exhibit in most solvents temperature-dependent 1H NMR spectra, while the spectrum of Ph 3SnCH 2CH 2SC 6H 4Me- p is essentially temperature-independent in carbon disulphide but not in carbon tetrachloride.

Wool graft copolymers initiated by azobisisobutyronitrile

AbstractGrafting of methyl methacrylate onto wool fibers using azobisisobutyronitrile as initiator has been investigated under a variety of conditions. Increasing the monomer concentration caused a significant increase in the graft yields. The same holds good for initiator concentration and reaction time, but to a lower degree. The grafting reaction was favorably influenced considerably by the nature of solvent used; it follows the order methanol > dimethylformamide > benzene. For practical significance, a mixture of water:methanol:DMF (75:24:1) was found to be the most effective medium for grafting. Presence of lithium chloride in the polymerization system favors grafting during the later stages of reaction, whereas presence of ceric sulfate was effective for higher grafting in the initial stages of reaction. Reduction of wool prior to grafting enhanced its ability to grafting; the latter increases in proportion to the thiol content. The opposite holds true for acetylation. Alkali solubility measurements reveal that an interaction between wool and methyl methacrylate in presence of AIBN took place.

Studies on Addition Reactions of Trimethyltin Hydride to Cyclobutene Derivatives and Structure of the Adducts

The addition reaction of trimethyltin hydride to methyl-3, 3-dimethyl-1-cyclobutene carboxylate (1a) or 3, 3-dimethyl-1-eyclobutene carbonitrile(1b) in the presence of AIBN was studied. The B-adducts(2a, 2b), were found consisting of trans adduct (76%) and cis adduct (24%), were obtained in 57 and 50%e yields respectively. Further, the preparation of dimethylbromotin. derivatives of (2 a) and (2b) was tried. The NMR spectra of stereoisomer obtained in this paper were also discussed.

Free‐radical‐induced polymerization of epoxides in the presence of maleic anhydride

AbstractThe free‐radical‐induced reactions of cyclohexene oxide in the presence of maleic anhydride have been found to lead to polyether in presence of AIBN and to a mixture of polyether, ester, and maleic anhydride adduct of polyether with di‐tert‐butyl peroxide (DTBP), the amounts of the mixture components depending on the concentration of DTBP and the temperature. Analogous reactions in the presence of succinic anhydride lead to no polyether. The obtained polyether has no hydroxyl group. The reaction appears to consist of three different steps, radical initiation, cationic propagation, and radical termination.

Mechanisms of propagation, transfer, and short‐chain branching reactions in the free‐radical polymerization of ethylene

AbstractThe propagation, transfer, and short‐chain branching reactions in the free‐radical polymerization of ethylene were studied at temperatures of 20–80°C. under pressures of 160–400 kg. cm.2 by means of two‐stage polymerization with the use of a specially designed reaction vessel. In the first stage, the polymerization was carried out in the presence of AIBN as the initiator, and in the second stage, the propagation occurred with living radicals in the absence of the initiator. In the second stage the polymer yield is shown to increase with reaction temperature and pressure, and the molecular weight of the polymer reached constant values which were dependent upon the temperature when the contribution of the polymer formed in the first stage was very small. It is shown that in the second stage the rate of propagation, transfer, and short‐chain branching are all proportional to the second power of ethylene fugacity, and that the activation energies of these reactions are 5.7, 23.4, and 10.9 kcal./mole, respectively. The polymer has no terminal vinyl group. The mechanism of these reactions is discussed on the basis of kinetic and energetic results.

GRAFT POLYMERIZATION OF ACRYLONITRILE ONTO VARIOUS FIBERS IMBIBING CATALYSTS

Various fibers imbibing solutions of several catalysts (K2S2O8, (NH4)2S2O8, H2O2, AIBN and BPO) were heated with pure acrylonitrile in sealed tubes. The heating was carried out for 50 hrs at 60°C or for 20 hrs at 80°C in air. Solvents for catalyst to be imbibed were water, water-methanol mixtures, methanol and benzene-petroleum benzine mixtures. Concentrations of the catalysts were 0.3_??_2%.The grafting onto cellulose fibers proceeded smoothly in the presence of persuiphates, but with difficulty in the presence of H2O2, AIBN and BPO. The efficiency of grafting onto viscose rayon was greater than that onto cotton. The grafting onto unheat-and heat-treated (at 200°C) polyvinyl alcohol fibers proceeded easily when the catalyst was (NH4)2S2O8 or H2O2, but with difficulty when the catalyst was AIBN or BPO. The grafting onto nylon fibers proceeded to a considerable extent only in the case of (NH4)2S2O8 catalyst.In contrast to the above mentioned fibers the grafting onto polyvinyl chloride fibers took place more smoothly in the presence of AIBN and BPO than in the presence of (NH4)2S2O8. The grafting of acrylonitrile onto polyester fibers was difficult throughout the experiments.Instead of pure acrylonitrile an acrylonitrile-dimethyl formamide mixture (1:1 by volume) or 20% aqueous solution of acrylonitrile was used for the grafting, but the degree of grafting was always lower than that obtained with pure acrylonitrile. The grafting onto dried fibers imbibing catalysts was also difficult.Generally the behaviors of grafting of acrylonitrile lay between those of styrene and vinyl acetate, and were rather near to those of vinyl acetate.