Separation and Structure of Methyl Methacrylate Telomers Synthesized in the Presence of Bromotrichloromethane

Kamewada

Kinoshita

et al. 1994

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ABSTRACT:The photolysis of dimethyl (2R*,4R*)-2-bromo-2,4-dimethyl-4-(2,2,2-trichloroethyl)glutarate was examined and reaction paths for ten products are proposed. A homolytic cleavage of the carbon-bromine bond of the substrate occurred first forming a radical intermediate and subsequent reactions yielded the products via decomposition of the intermediate and recombination of secondly formed radical species. Ionic lactonization of the substrate and diastereoisomerization proceeded simultaneously.KEY WORDS Photolysis / Telomer / Methyl Methacrylate Dimer Homolytic Cleavage / Carbon-Bromine Bond / Recombination Diastereoisomerization / Lactonization / The photochemistry of organic halides is characterized by cleavage of the carbon-halogen bond. 1 · 2 In recent studies on the solution photoreaction of aliphatic halides, 3 -5 workers have concentrated their attention on understanding whether the products are formed from a radical species or from an ionic one.We previously reported the photolysis of methyl 2-bromo-4,4,4-trichloro-2-methylbutyrate (1) 6 obtained from the telomerization of methyl methacrylate (MMA) using bromotrichloromethane (BTCM) as a telogen. 7 In the preceding paper,8 we described the effects of copper powder on the photolysis of 1. The results indicated that the conversion of the substrate and amount of products via a homolytic cleavage of the carbon-bromine bond increased with the amount of copper powder added. Since there have been a few studies on the photochemistry of aliphatic * To whom all correspondence should be addressed.halides containing different halogen atoms, 9 • 10 we had interest in the photochemistry of telomers such as 1.meso-and di-Dimers of MMA with a headto-head linkage, formed by recombination of the tertiary carbon radicals produced by a homolytic cleavage of the carbon-bromine bond, are interesting. Rae et al. reported the synthesis and characterization of the mesoand di-isomers of tetramethyl 2,4,5,7-tetramethyloctane-2,4,5, 7-tetracarboxylate and thermal degradation of its meso-isomer as a model to study the effects of head-to-head linkage in thermal degradation of poly-(MMA). 11,12

Section: Methodsmentioning

confidence: 99%

Section: Characterization Of the Productsmentioning

confidence: 99%

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Photochemical Transformation of Telomers III. Photolysis of Dimethyl (2R,4R)-2-Bromo-2,4-dimethyl-4-(2,2,2-trichloroethyl)glutarate

Kamewada

Kinoshita

et al. 1994

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“…This product was identical to an authentic sample. 4 Methyl Table I shows the effect of irradiation time on the photolysis of 1 in methanol at 30°C. The conversion yield of 1 and the production yields of all photoproducts increased gradually with irradiation time.…”

Section: Characterization Of the Photoproductsmentioning

confidence: 99%

Photochemical Transformation of Telomers I. Photolysis of Methyl 2-Bromo-4,4,4-trichloro-2-methylbutyrate

Hamashima

1989

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ABSTRACT:The photochemical reaction of methyl 2-bromo-4,4,4-trichloro-2-methylbutyrate (1) was studied aiming at its chemical modification. The effects of irradiation time, temperature, and solvent polarity on the photolysis of 1 were investigated. The formation of ten photoproducts was confirmed, and the route of photolysis is proposed. Homolytic cleavage of the carbon-bromine bond occurred predominantly to induce different types of photoprocesses, such as disproportionation, elimination, hydrogen abstraction, recombination, and addition. The elimination reaction proceeded contrary to Saytzeff's law, and the debromine-coupling and addition reactions gave some novel dimeric telomers. KEY WORDSPhotochemical Transformation / Methyl 2-Bromo-4,4,4-trichloro-2-methylbutyrate / Photolysis / Cleavage of Carbon-Bromine Bond / Photodimerization / Head-to-Head Orientation / Diastereoisomer / Lactonization / The photochemistry of halides has been extensively studied,1, 2 but there have been reported few studies on the photochemical reactions of aliphatic compounds containing plural diverse halogens. 3 In the previous papers,4· 5 we reported the radical telomerization of a series of alkyl methacrylates using bromotrichloromethane (BTCM) as a telogen and the characteristics of the resulting telomers up to trimers. The resulting telomers can be utilized as "reactive oligomers" by chemical modification of their functional groups. For example, the pyrolysis and hydrolysis of the corresponding dimeric telomers easily gave y-lactones, which are useful as unique polycondensing oligomers by carboxylation of their residual functional groups. 6 The object of this work was to elucidate the photolysis behavior of methyl methacrylate (MMA) monomer telomerized with BTCM, that is, methyl 2-bromo-4,4,4-trichloro-2-methylbutyrate (1), and to find valuable oligomers in the field of polymer science. The effects of irradiation time, temperature, and solvent polarity on the photolysis of 1 are discussed, and the route of the photolysis is considered on the basis of the structural analysis of the photoproducts. EXPERIMENT AL MeasurementsMelting points were measured with a Yamato MP-21 melting point apparatus. Boiling points were determined during distillation. UV spectra were recorded with a Shimazu UV-180 spectrophotometer. IR spectra were measured on a KBr plate or in KBr disks with a Hitachi 295 spectrophotometer. 1 H NMR spectra were determined with a JEOL JNM-C-60HL spectrometer (60MHz) using Me 4 Si as an internal standard. Mass spectra were taken on a Hitachi M-80 spectrom-91

“…The reaction mixture was treated by a similar manner as described in the previous paper. 6 Commercial VMA and AMA were purified by a conventional method. Commercial BTCM was purified by distillation under reduced pressure, and AIBN by recrystallization from methanol.…”

Section: Telomerization Proceduresmentioning

confidence: 99%

Study on Radical Telomerization of Esters of Methacrylic Acid Using Bromotrichloromethane and Characteristics of the Resulting Telomers VI. Difunctional Methacrylates

Hamashima

1988

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ABSTRACT:The radical telomerization of vinyl (VMA) and ally! (AMA) methacrylates was carried out using bromotrichloromethane (BTCM) as a telogen at 50, 70, and 90°C. The m [Cl 3 CBr]:n[Monomer]adducts (m=l, 2, 3; n=I, 2) were fractionated by means of silica gel column chromatography. Compared with VMA, AMA was subject to addition of BTCM and telomerized with a lower average degree of telomerization. The addition of BTCM occurred on both the vinylidene and vinyl groups, but the vinylidene group was much more susceptible to addition of BTCM in preference to the vinyl group. Furthermore, the chain of dimeric adducts was exclusively made up by a vinylidene--vinylidene coupling. The successive addition reaction of BTCM to telomeric molecules increased with temperature, time, and quantity of 2,2'-azobisisobutyronitrile (AIBN) as an initiator. In the telomerization at 90°C, however, the addition rate of BTCM decreased in response to rapid inactivation of AIBN. The lactonization of dimeric adducts (m =I, n = 2) was induced by the catalytic action of silica gel or heating. The lactone yield of the AMA adducts was higher than that of the VMA one. The VMA adduct was preferentially oligomerized by pyrolysis at l 50°C. KEY WORDSRadical Telomerization / Difunctional Monomers / Vinyl Methacrylate / Ally! Methacrylate / Bromotrichloromethane / Telomerization Behavior / Structure of Adducts / Tacticity / Addition / Lactonization / Bromotrichloromethane (BTCM) is known as an effective telogen for the radical telomerization of vinyl monomers by kinetic studies. 1 -5 However, there have been reported few studies on the telomerization behavior of vinyl monomers using BTCM as a telogen and characteristics of the resulting telomers.In previous papers, 6 -10 we reported the radical telomerization of eleven kinds of monofunctional methacrylates using BTCM as a telogen. The effects of the substituent in the ester group on the telomerization behavior of these monomers and characteristics of the resulting telomers were systematically studied.The telomerization behavior of alkyl methacrylates and reactivity of the resulting telomers were greatly dependent on the degree of branching rather than the length of the alkyl chain. In particular, t-butyl methacrylate showed its own characteristics in many respects. On the other hand, the telomerization behavior of aryl methacrylates, except for 9-fluorenyl methacrylate, resembled that of primary alkyl methacrylates in distribution of degree of telomerization (MWD) and tacticity.However, the apparent rate of telomerization of aryl methacrylates was lower than that of alkyl methacrylates in general. Furthermore, t Part I-V of this series are ref 6-10. 45