Polyaddition of Dithiol Compounds to Divinyl Compounds: The Kinetics of the Model Addition Reaction of Thiophenols to Styrenes

Takayanagi

Ohashi

et al. 1991

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ABSTRACT:The mechanisms of cis polyaddition of I ,4-benzenedithiol to 1 ,4-diethynylbenzene were studied by means of a model reaction. As the model reaction, the addition reaction of thiophenol (TP) to ethynylbenzene (EB) was carried out in a NMR glass tube at 34oC under atmosphere of nitrogen and the reaction course was monitored by 1 H NMR method. Under an atmosphere of nitrogen an anti-Markownikoff type product, /J-phenylthiostyrene, with 80% of the cis structure was obtained at various molar ratios of TP to EB. On the other hand, under an atmosphere of air, the addition reaction proceeded almost quantitatively for 4h to form the anti-Markownikofftype adduct, which was initially rich in the cis structure, but cis content decreased gradually to below 50% even after the hundred conversion. In the case of the polyaddition of I ,4-benzenedithiol to 1 ,4-diethynylbenzene, high cis polymers were obtained initially both in solution and also in solid state polymerization. Consequently, the cis polymerization mechanism is the same as the cis adduct formation. MIND013 calculations with intermediates and products indicated that the trans adduct is more stable that the cis adduct, while the intermediate radical for the cis adduct (cis*) is 3.4 kca1 mol-1 lower than that for the trans adduct (trans*). Accordingly, the cis adduct and cis vinylene of the polymer are preferentially formed by kinetic control. The effects of oxygen, thiophenol, AIBN and reaction temperature on the isomerization of the cis to trans adduct were also studied by 1 H NMR method. It was found that the isomerization of the cis to trans adduct hardly occurred in the absence of oxygen, AIBN or phenylthio radical at 34oC. The free radical addition reactions of thiols to acetylenes have been carried out under several conditions. In the case of aromatic acetylene, it was found that the addition reaction took place easily to yield l ,2-disubstituted ethenes in an anti-Markownikoff manner , 1 -3 But, the cis-trans ratio ofproduc_ts was affected by reaction conditions such as temperature, 4 • 5 atmosphere, time and a molar ratio of thiols to acetylenes. 6 Oswald 6 studied the addition reaction of thiophenol to ethynylbenzene at various molar ratios at ooc with UV-irradiation for 2 h. It was found that a high excess of ethynylbenzene over thiophenol (1.1 : 0.05) resulted in the formation of a high cis content mixture (more than 95%). However, a high excess of thiophenol over ethynylbenzene (0.05 : 1.0) resulted in the formation of a low cis content mixture (ca. 16%). These results do not clearly indicate whether the ratio of the cis and trans adducts is controlled by the molar ratio of ethynylbenzene and thiophenol or the cis adduct produced is isomerized to the trans adduct.Previously, the authors reported the poly-1029

Section: Addition Reaction Of Tp To Ebsupporting

confidence: 62%

“…16 Oxygen, radical initiators, and UVlight initiate the thiophenyl radical forma- tion. The rate determining step is the addition reaction of thiophenyl radical to EB.…”

Section: Addition Reaction Of Tp To Ebmentioning

confidence: 99%

Cis Addition Reaction of Thiophenol to Ethynylbenzene and Isomerization of Adduct as a Model of Poly(1,4-benzenedithiol-co-1,4-diethynylbenzene)

Takayanagi

Ohashi

et al. 1991

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“…The rate-determining step and substituent effect on the addition reactions were determined and compared with those on the addition reaction of thiophenol (TP) to St 7 or EB. 8 • 9 EXPERIMENT AL Reagents p-Methoxy, p-methyl, and p-chloro TBAs were prepared by the modified synthetic method for TBA 10 as follows: a solution of 25 g (0.15 mol) of p-methoxybenzoylchloride (Aldrich Chem.…”

mentioning

confidence: 99%

Kinetics of the Addition Reactions of Thiobenzoic Acids to Styrenes or Ethynylbenzenes as the Model of Polyaddition. Study on the Rate-Determining Step and Substituent Effect

Shimizu

Obata

et al. 1993

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“…The addition reactions of BSe or BT to EB have the same reaction orders; that is, the rate-determining step is the addition step of the benzeneseleno radical (see eq 6) or the benzenethiyl radical to EB. In the addition reaction of BT to styrene (St) 19 or addition reactions of diphenylphosphine to St 20 and EB, 21 the rate-determining step was the chain transfer step between the intermediate carbon radicals and BT or diphenylphosphine. According to quantum chemical calculation by CAChe system, the rate-determining step was expected to be the chain transfer step in the addition reaction of BT to EB.…”

Section: Comparison Between Bse and Bt Or Eb And St I) Comparison Betmentioning

confidence: 99%

Novel Conjugated Polymer Containing Aromatic Ring and Selenium in Backbone. Kinetics of the Addition Reaction as the Model for Addition Polymerization

Metaka

Aoshima

et al. 1995

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ABSTRACT:The addition reaction mechanism of benzeneselenol to ethynylbenzene was studied as a model for the addition polymerization (so called polyaddition) of 1,4-benzenediselenol to 1,4-diethynylbenzene. The addition reaction occurred without an appreciable side reaction in the presence of AIBN and an adduct of the anti-Markownikoff's structure ( 0-Se-CH = CH---0) was quantitatively obtained. The addition reaction is very similar to the addition polymerization of 1,4-benzenediselenol to 1,4-diethynylbenzene from the point of the geometrical structure of the polymer chain. A kinetic study showed that a rate-determining step of the addition reaction was the addition step of the benzeneseleno radical to ethynylbenzene. The results were compared with those of the addition reaction of benzenethiol to ethynylbenzene. By the competitive addition reaction, ethynylbenzene had 80 times higher reactivity than styrene toward benzeneselenol at 60°C in benzene.KEY 1,4-benzenedithiol (BDT) to 1,4-diethynylbenzene (DEB) proceeded rapidly in solution 4 or in solid state 7 under UV-irradiation. A conjugated linear polymer of the antiMarkownikoff's structure was obtained. The thin polymer film obtained by the solid state polymerization had a layer structure. The layer structure of polymer films increased or decreased reversibly by irradiation of the characteristic light. 8 In the previous paper,9 the authors investigated the synthesis of the conjugated polymer containing selenium by the addition polymerization of 1,4-benzenediselenol (BDSe) to DEB as shown in eq I. The polymerization of BDSe to DEB was carried out by UV-irradiation in toluene at 60°C under The authors reported studies on the conjugated polymer containing sulfur by addition polymerization (so called polyaddition) of dithiol monomers to diethynyl monomers. 4 -6