Radiation-induced addition reaction of carbon tetrachloride onto 1,2-polybutadiene

The γ-ray-induced addition reaction of carbon tetrachloride onto syndiotactic 1,2-polybutadiene film and liquid 1,2-polybutadiene was carried out at room temperature. In the film gelation was pronounced and the rate of addition increased as the crystallinity of the polymer decreased. In the liquid gelation, which makes the polymer insoluble in carbon tetrachloride, did not take place, although a definite crosslinking reaction was noticed. In this case the appearance of the product changed from a viscous liquid to a white powder as the reaction proceeded. Its structure was compared with that of chlorinated 1,2-polybutadiene. The addition of carbon tetrachloride to the vinyl group in liquid 1,2-polybutadiene caused an anti-Markownikoff-type reaction and was accompanied by an unexpectedly large vinyl depletion in the polymer. The total decrease in the vinyl group was found to be much larger than that brought about by the addition of carbon tetrachloride. This discrepancy was attributed to a cyclization and crosslinking reaction ascribed to the vinyl group bound by the main chain. Cyclization and crosslinking were less noticeable in the chlorination than in the carbon tetrachloride.     

Radiation-Induced Addition Reaction of Ethyl Mercaptan and Carbon Tetrachloride to 1,2-Polybutadiene

γ-Ray-induced addition reactions of syndiotactic 1,2-polybuta-diene film with various compounds were carried out at room temperature. The weight of the film markedly increased when ethyl mercaptan was used. In the reaction with ethyl mercaptan, only addition took place without crosslinking. The addition of ethyl mercaptan to the vinyl group of syndiotactic 1,2-poly-butadiene followed anti-Markownikoff rule, and gave a 1:1 addition product. The rate of addition increased as the crys-tallinity of syndiotactic 1,2-polybutadiene used became lower. A similar relation between the crystallinity and the rate of addition was also observed in the γ-ray-induced addition of carbon tetrachloride to syndiotactic 1,2-polybutadiene, but at the same time gelation was pronounced. When liquid 1,2-polybutadiene was used instead of syndiotactic-1,2-polybutadiene, gelation which made the polymer insoluble in carbon tetrachloride did not take place, although a crosslinking reaction was noted. The appearance of the product in this case changed from a viscous liquid to a white powder as the reaction proceeded. The addition of carbon tetrachloride to the vinyl group of liquid 1,2-polybutadiene was also of the anti-Markownikoff type. This addition was accompanied by unexpectedly large vinyl consumption. The total decrease in vinyl group was found to be much larger than the decrease in vinyl group which was brought about by the addition of carbon tetrachloride. This discrepancy was attributed to cyclization and crosslinking reactions which were ascribed to the vinyl group bound by the main chain.     

Radiation-induced crosslinking and cyclization in 1,2-polybutadiene

In order to get information on the radiolytic changes in 1,2-polybutadiene (1,2-PB) the sol and gel fractions, the conversion of double bonds, the structure and concentration of radicals, the formation of dienes and the formation of gaseous products were measured. In addition, the dose rate dependence and temperature dependence for the conversion of double bonds were determined. G values for double bond conversion depend on molecular weight and range from 20 to 200. G values for crosslinking are about 10. A mechanism for the double bond conversion is proposed which involves initiation by a transformation of the primary radical ion in the vinyl group into a carbonium ion and a radical. This is supported by ESR measurement. Reaction of the carbonium ion with a vinyl group in the same chain gives rise to cyclization, whereas reaction with a vinyl group in a neighboring chain results in crosslinking. A comparison of the G values for conversion of double bonds with the G values for crosslinking shows that the formation of cyclic rings exceeds the formation of crosslinks by a factor of about 10. The corresponding values in 1,4-cis- and 1,4-trans-polybutadiene are much smaller [G(cl) ? 2; G(db) ? 7]. The pendent vinyl groups in 1,2-polybutadiene therefore are more reactive than the vinylidene groups in 1,4-polybutadienes.     

A solid-state 13C-NMR study of crosslinking in polybutadiene by γ radiation: Effect of microstructure and dose

Solid-state ¹³C NMR spectroscopy has been used to determine the decrease in C?C bonds, formation of crosslinks and cis to trans isomerization during the γ irradiation of (a) > 99% cis, 1,4-polybutadiene, (b) 54% trans, 41% cis, 1,4-polybutadiene, and (c) 86% 1,2-polybutadiene. G(-cis C?C) and G(-trans C?C), were similar and decreased with dose from ≈ 40 for 0-1 MGy to 5 for 5-10 MGy. G(-double bonds) and G(crosslink) were comparable, indicating that crosslinking occurred through the double bonds. G(crosslink) was much higher than values derived from physical properties, confirming that NMR measures the total of inter- and intramolecular crosslinking (cyclization). The 1,2 polybutadiene was much more sensitive to crosslinking, and a value of G(-C?C) = 240 was obtained at low doses. Crosslinking evidently proceeds by a kinetic chain reaction in all three types of polybutadiene.     

Syndiotactic 1,2-polybutadiene with Co-CS2 catalyst system. I. Preparation,properties, and application of highly crystalline syndiotactic 1,2-polybutadiene

Highly crystalline syndiotactic 1,2-polybutadiene (s-PB) having melting point (mp) up to 216°C was obtained by using a Co(acac)₃-AIEt₃-CS₂ catalyst. The polymer with mp 208°C was found to have 99.7% 1,2 content and 99.6% syndiotacticity by ¹H and ¹³C-NMR measurements. The s-PB can be molded by addition of a stabilizer such as 2,6-di-t-butyl-4-hydroxymethylphenol into fiber, film, and various shaped articles. The physical properties presented in the present article include stress-strain and dynamic mechanical behavior. The highly crystalline syndiotactic 1,2-polybutadiene was applied to a carbon fiber and UBEPOL VCR (cis-1,4-polybutadiene reinforced by fibrous syndiotactic 1,2-polybutadiene).     

Reactivity studies of ethyl(Z)‐N‐(2‐amino‐1,2‐dicyanovinyl) formimidate with carbonyl compounds in the presence of base

The reaction of ethyl(Z)‐N‐(2‐amino‐1,2‐dicyanovinyl)formimidate 6 with carbonyl compounds in the presence of triethyl amine occurs with formation of the Schiff s base and intramolecular hydrolysis of the adjacent cyano group to give the alkylideneamino derivatives 8a‐f . When the α‐carbon of the ketone has at least one proton, the prolonged contact of 8a‐f with triethylamine causes intramolecular cyclization between this carbon and the imidate carbon atom to form a seven membered ring. This is followed by cyclization of the cyano and amido groups, leading to the pyrrolo[4,3‐b][1,4]diazepines 9 . If a strong base is used the first ring to be formed is the pyrrole ring as evidenced in the reaction of 8a with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene leading to 14 . The subsequent addition of methyl amine to the reaction mixture, caused cleavage of the alkylideneamino unit and formation of the amidine function from the imi date ( 15 ). The addition of acid to the imidates 8a and 8f led to the diazepine compounds 10a and 10f respectively. A suspension of compound 8e in ethanol and triethylamine evolved to a pyrazinone structure 12 under kinetic conditions (4 hours, room temperature) and to the pyrrolo[4,3‐b][1,4]diazepine 9e under thermodynamic conditions (48 hours, room temperature).     

The reaction of trichloromethyl radicals with hydrogen chlorid and a new estimation of the rate of combination of trichloromethyl radicals

The effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio k₈/(k₅)^1/2 to be determined. Since k_?8 is well established, k₅ can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined: The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.     

Kinetic studies of nonaqueous polymerization of methyl methacrylate initiated by ferric laurate–n-hexyl amine system

The polymerization of methyl methacrylate was studied in carbon tetrachloride medium with ferric laurate, a metal soap, in combination with n-hexyl amine as the initiator system at 60°C. The rate of polymerization was found to be linear with the monomer concentration and proportional to the square root of both ferric ion and amine concentration. A reaction scheme involving initial complex formation between ferric ion and amine and subsequent reaction of the complex with the solvent molecule to produce free radicals responsible for initiation of polymerization has been postulated to account for the observed results.     

Study on the chain conformation of polymers.: II. Conformational characteristics of 1,2-polybutadiene and its characteristic ratio

In this work, improvement was made for conformational analysis of 1,2-polybutadiene by means of the molecular mechanics force field program (MM2). Thus the first and the second order interaction energies obtained are much more reasonable. The characteristic ratio of isotactic 1,2-polybutadiene was emphasized properly, which varied with energy E (E = E_η + E_ω″). In the same time, the characteristic ratios for isotactic chain of polystyrene and so on were noticed, which varied with energy E according to the same way as that for isotactic 1,2-polybutadiene. It is shown that there is a general rule or a common feature for isotactic chains of poly -α-olefine and vinyl polymer.     

Microwave‐Assisted Tandem Transformation on an Ionic‐Liquid Support: Efficient Synthesis of Pyrrolo/Pyridobenzimidazolones and Isoindolinone‐Fused Benzimidazoles

A tandem transformation that involves the formation of three bonds and two heterocyclic rings in a one‐pot fashion through amino‐alkylation of an ionic‐liquid‐immobilized diamine with keto acids followed by successive double intramolecular cyclizations to afford a tricyclic framework has been explored. This tandem cyclization has been utilized to develop a rapid and efficient method to synthesize various pyrrolo[1,2‐a]benzimidazolones and pyrido[1,2‐a]benzimidazolones on an ionic‐liquid support by using focused microwave irradiation. The application of this tandem cyclization was further extended to the aromatic keto acids to provide isoindolinone‐fused benzimidazoles, a structurally heterogeneous library with skeletal diversity. The outcome of the cascade reaction was confirmed by the X‐ray crystallographic study of the product directly attached to the ionic‐liquid support. Use of the ionic liquid as a soluble support facilitates purification by simple precipitation along with advantages like high loading capacity, homogeneous reaction conditions, and monitoring of the reaction progress by regular conventional spectroscopic methods, whereas application of microwave irradiation greatly accelerates the rate of the reactions.     

Synthesis and chemical reactivity of indenoisoxazoles

Treatment of 2-pivaloyl-1,3-indandione ( 1 ) with hydroxylamine under acidic conditions, results in formation of 8-t-butylindeno[1,2-c]isoxazol-7-one ( 2 ) while treatment of the triketone with hydroxylamine at neutral or basic pH gave 6 which upon cyclization gave the isomeric 3-t-butylindeno[1,2-c]isoxazol-4-one ( 7 ). Compound 7 was readily reduced to amine 12 by treatment with hydrazine or hydrogen over platinum. The amine, although quite unreactive, was converted to 3-t-butylindeno[1,2-c]pyrazol-4-one ( 13 ) with hydrazine or reduced to 15 and 16 with sodium in liquid ammonia and alcohol. Surprisingly, the amine 3 obtained from isoxazole 2 gave reduction product 15 from a sodium-liquid ammonia reduction and not the expected product 18. Spectral evidence for each of the structures is discussed.     

Photochemistry of acetylene derivatives of aromatic amines 2. Photolysis of p-ethynyl- and p-butadiynyl-N,N-dibenzylanilines and p-dimethylaminotolane in the presence of carbon tetrachloride and oxygen

The radicalcations of alkynylanilines are formed during the photolysis of ethynylanilines substituted at the para position in the presence of carbon tetrachloride and oxygen. They undergo two types of reaction, i.e., ejection of the alkyl substituent from the amino group and addition of the H atom from the amine molecule or the Cl atom from the carbon tetrachloride to the triple bond of the radicalcation. In the radicalcation of p-butadiynyl-N,N-dibenzylaniline not only the N-Alk but also the N-Ar bond is cleaved. The mass spectra of the products from the photolysis of all the investigated alkynylarylamines were obtained and analyzed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1091–1098, May, 1990.     

Photorearrangements of hydrocarbon polymers with pendant double bonds

A study was made of the microstructural changes that occur in ultraviolet irradiation under vacuum of thin films of 1,2-poly(cis-1,4-hexadiene) (CHD), 1,2-poly(trans-1,4-hexadiene) (THD), 1,2-poly(trans-1,3-pentadiene) (TPD), equibinary (1,2,-1,4) polybutadiene (EB), and equibinary (3,4-1,4) polyisoprene (EI). These polymers—all containing pendant double bonds—undergo important photoinduced loss of unsaturation, presumably through cyclization of the double bonds, by analogy to the previously reported photocyclization of 1,2-polybutadiene (VB) and 3,4-polyisoprene (VI)films. For the equibinary polymers, which contain internal as well as external (or pendant) double bonds, the loss of unsaturation is considered to involve photocyclization of 1,2-1,4 and 1,2-1,2 dyads in EB and of 3,4-1,4 and 3,4-3,4 dyads in EI. Accompanying thecyclization process in CHD, THD, and TPD is a direct photochemical cis-trans isomerization of ? CH?CH? double bonds analogous to that originally noted for 1,4-polybutadiene. The photorearrangements in the above polymers with pendant double bonds were compared to the corresponding thermally induced rearrangements reported previoulsy;for VB and VI, in particular, the thermal, photo-and radiation-induced cycli-zations were found to be very similar, possibly having a common nonradical, nonionic mechanism involving excited double bonds.     

Lewis acid-promoted Kharasch-Curran additions: a competition kinetics study of bromine atom transfer addition of N-alpha-bromoacetyl-oxazolidinone to 1-hexene

Lewis acids can efficiently promote free radical atom transfer reactions of an oxazolidinone imide substrate, 1, derived from alpha-bromo acetic acid. Thus, 1 undergoes a radical chain addition to 1-hexene giving the atom transfer addition compound, 6, in the presence of scandium or ytterbium triflate in 1,2-dichloroethane or a cosolvent mixture of 1/9 THF/dichloromethane. In 1,2-dichloroethane the solution is heterogeneous, while the cosolvent mixture gives a homogeneous solution, even at temperatures of -78 degrees C. Competition experiments were carried out in both solvent systems with added carbon tetrachloride to study how Lewis acid affected the product distribution. In the presence of carbon tetrachloride, chloride 7 is formed in addition to 6 and the ratio of these two products depends on the amount of Lewis acid present. In the presence of ytterbium triflate, in the cosolvent system, the reaction rate of bromine atom transfer was enhanced up to 400-fold compared to the reaction without added Lewis acid. Significant rate enhancements were also obtained in the solvent 1,2-dichloroethane, although the analysis of the system is complicated by the heterogeneous nature of the medium. Computation of C-Br bond dissociation energies (BDE) of the complexed and uncomplexed oxazolidinone bromide suggest that complexation lowers the BDE due to the effect of the strong electron-withdrawing group on the C-Br bond dipole.     

Stereoregularity of poly(isopropyl acrylate) and its racemization during hydrolysis

The diad tacticity of poly(isopropyl acrylate) was measured from the β-proton absorptions of poly(isopropyl acrylate-α,β-d₂) obtained with a 100 MHz NMR spectrometer, and temperature dependence of the tacticity of the polymers obtained by radical polymerization was determined. Enthalpy and entropy differences between isotactic and syndiotactic addition for poly(isopropyl acrylate) were calculated to give the following values: Δ(ΔS) = 0.7 eu; Δ(ΔH) = 0.51 kcal/mole. In the hydrolysis of poly(isopropyl acrylate-α,β-d₂), it was found that the rate of hydrolysis of poly(isopropyl acrylate) was dependent on the molecular weight rather than on the tacticity. As for the rate of racemization during hydrolysis, the rate for syndiotactic polymer was much faster than that for the isotactic polymer. The exchange reaction of deuterium at α-position with hydrogen occurred in all the polymers during hydrolysis reaction.     

Oxidation of Methyl Function of 3,3-(3-Fluorobenzyl)-2-Propanone by Thionyl Chloride

In the presence of a catalytic amount of a tertiary amine, thionyl chloride generally oxidizes carboxylic acids^1,2 and ketones¹ at α carbon atoms to form α-chloro-α-chlorosulfenyl derivatives and their subsequent reaction products. Examination of reaction mixtures of thionyl chloride with a number of variously substituted 4-aryl-2-butanones revealed that in the case of the 3-methoxy or 3-hydroxy derivatives, cyclization onto the aromatic ring to form a benzo[b] thiophene competes quite favorably with cyclization onto enol to form a thietanone.⁴ The results were consistent only with thionyl chloride oxidation proceeding exclusively at the methylene position.     

Bifunctionalized Allenes,Part XI: Competitive Electrophilic Cyclization and Addition Reactions of 4‐Phosphorylated Allenecarboxylates

The reaction of the 4‐phosphorylated allenecarboxylates with different electrophilic reagents such as sulfuryl chloride, bromine, benzenesulfanyl, and benzeneselanyl chlorides takes place with a 5‐endo‐trig cyclization or 2,3‐addition reaction depending on the kind of the substituents in the phosphoryl group. Treatment of the 4‐(dimethoxyphosphopyl)‐allenoates with electrophiles gives a mixture of 2,5‐dihydro‐1,2‐oxaphospholes and furan‐2(5H)‐ones in the ratio of about 1.7:1 as a result of the neighboring group participation of phosphonate and carboxylate groups in the cyclization. On the other hand, (3E)‐4‐(diphenylphosphoryl)‐alk‐3‐enoates were prepared, in moderate yields, by chemo‐, regio, and stereoselective electrophilic addition to the C² C³‐double bond in the allenoate moiety. A possible mechanism involving cyclization and addition reactions of the 4‐phosphorylated allenecarboxylates was proposed.     

Peculiarities of three-component cyclization of ethyl 4,4,4-trifluoroacetoacetate and 1,2-ethanediamines with 3-methylbutan-2-one

The peculiarities of the three-component cyclization of ethyl 4,4,4-trifluoroacetoacetate and 1,2-ethanediamines with 3-methylbutan-2-one into hexahydroimidazo[1,2-a]pyridin-5-ones were studied. The reactions proceeded under mild conditions. The use of methyl ketone with a bulky isopropyl substituent increased the stereoselectivity of the transformations, but the reaction with 1,2-diaminopropane was accompanied by the formation 4-[(1-ammoniopropan-2-yl)amino]-1,1,1-trifluoro-4-oxobut-2-en-2-olate as a by-product.

     

Diastereo‐ and Regioselective Addition of Thioamide Dianions to Imines and Aziridines: Synthesis of N‐Thioacyl‐1,2‐diamines and N‐Thioacyl‐1,3‐diamines

Addition reactions of thioamide dianions that were derived from N‐arylmethyl thioamides to imines and aziridines were carried out. The reactions of imines gave the addition products of N‐thioacyl‐1,2‐diamines in a highly diastereoselective manner in good‐to‐excellent yields. The diastereomeric purity of these N‐thioacyl‐1,2‐diamines could be enriched by simple recrystallization. The reduction of N‐thioacyl‐1,2‐diamines with LiAlH₄ gave their corresponding 1,2‐diamines in moderate‐to‐good yields with retention of their stereochemistry. The oxidative‐desulfurization/cyclization of an N‐thioacyl‐1,2‐diamine in CuCl₂/O₂ and I₂/pyridine systems gave the cyclized product in moderate yield and the trans isomer was obtained as the sole product. On the other hand, a similar cyclization reaction with antiformin (aq. NaClO) as an oxidant gave the cis isomer as the major product. The reactions of N‐tosylaziridines gave the addition products of N‐thioacyl‐1,3‐diamines with low diastereoselectivity but high regioselectivity and in good‐to‐excellent yields. The use of AlMe₃ as an additive improved the efficiency and regioselectivity of the reaction. The stereochemistry of the obtained products was determined by X‐ray diffraction.     

Electrodialysis Separation of Copper(II) and Platinum(IV) with Liquid Membranes Based on Di(2-Ethylhexyl)Phosphoric Acid

Separation of copper(II) and platinum(IV) in extraction from binary acid chloride solutions with liquid membranes containing technical-grade di(2-ethylhexyl)phosphoric acid with addition of tri-n-octyl amine in 1,2-dichloroethane under the conditions of the galvanostatic electrodialysis was studied. The influence exerted by the current density and composition of aqueous solutions and liquid membranes on the rate and selectivity of copper(II) extraction was analyzed. The optimal conditions of metal separation were determined.