Synthesis of Structurally Controlled, Highly Branched Polymethacrylates) by Radical Polymerization Through the Design of a Monomer Having Hierarchical Reactivity

The controlled synthesis of highly branched (HB) poly(methyl methacrylate) (PMMA) with a molecular weight of up to 88 × 10³gmol and low dispersity (<i>Ð</i> < 2.0) was achieved by the radical copolymerization of vinyltelluride, H₂C=CHTePh (<b>4cD</b>), and MMA in the presence of the organotellurium chain transfer agent <b>6cI</b> at 30 °C. Control of the branching structure was suggested by the Mark-Hauwink-Khun-Sakurada plots corresponding to samples in solution and trapped ion mobility spectroscopy-time of flight mass spectrometry in the gas phase. The mechanism of <b>4cD</b> for the structural control of HB-PMMA synthesis comes from the hierarchical reactivity of the C-Te bond of <b>4cD</b>, which serves as the branching point only after <b>4cD</b> reacts and is incorporated into the polymer chain. In contrast, copolymerization using previously reported vinyltellurides <b>4aA</b> (H₂C=C(Me)TeMe) and <b>4aB</b> (H₂C=C(Me)-CH=CHTeMe) could not control the branching structure due to the <i>b</i>-carbon fragmentation reaction from the intermediate radicals generated from <b>4aA</b> and <b>4bB</b>. The theoretical calculations suggest that the suppression of the undesired fragmentation reaction when using <b>4cD</b> is due to the acceleration of the desired propagation reaction forming a branched structure instead of decelerating the fragmentation reaction. Due to the versatility of radical polymerization, methacrylates with bulky substituents, such as <i>t</i>-butyl methacrylate, and polar functional groups, such as <i>N,N</i>-dimethylethyl methacrylate (DMAEM), were also used as monomers to afford structurally controlled corresponding HB polymers. These studies clearly open a new possibility for the use of HB polymers in macromolecular engineering.

Synthesis of Structurally Controlled, Highly Branched Polymethacrylates) by Radical Polymerization Through the Design of a Monomer Having Hierarchical Reactivity

The controlled synthesis of highly branched (HB) poly(methyl methacrylate) (PMMA) with a molecular weight of up to 88 × 10³gmol and low dispersity (<i>Ð</i> < 2.0) was achieved by the radical copolymerization of vinyltelluride, H₂C=CHTePh (<b>4cD</b>), and MMA in the presence of the organotellurium chain transfer agent <b>6cI</b> at 30 °C. Control of the branching structure was suggested by the Mark-Hauwink-Khun-Sakurada plots corresponding to samples in solution and trapped ion mobility spectroscopy-time of flight mass spectrometry in the gas phase. The mechanism of <b>4cD</b> for the structural control of HB-PMMA synthesis comes from the hierarchical reactivity of the C-Te bond of <b>4cD</b>, which serves as the branching point only after <b>4cD</b> reacts and is incorporated into the polymer chain. In contrast, copolymerization using previously reported vinyltellurides <b>4aA</b> (H₂C=C(Me)TeMe) and <b>4aB</b> (H₂C=C(Me)-CH=CHTeMe) could not control the branching structure due to the <i>b</i>-carbon fragmentation reaction from the intermediate radicals generated from <b>4aA</b> and <b>4bB</b>. The theoretical calculations suggest that the suppression of the undesired fragmentation reaction when using <b>4cD</b> is due to the acceleration of the desired propagation reaction forming a branched structure instead of decelerating the fragmentation reaction. Due to the versatility of radical polymerization, methacrylates with bulky substituents, such as <i>t</i>-butyl methacrylate, and polar functional groups, such as <i>N,N</i>-dimethylethyl methacrylate (DMAEM), were also used as monomers to afford structurally controlled corresponding HB polymers. These studies clearly open a new possibility for the use of HB polymers in macromolecular engineering.

MEKANISME REAKSI FRAGMENTASI SENYAWA KIMIA DALAM KULIT BUAH ALPUKAT (Persea americana Mill.)

ABSTRACTInvestigation of the fragment structure of ions and fragmentation reaction is crucial and needs to be done to reconstruct the chemical structure of the examined sample. Therefore, it is necessary to study the fragmentation mechanisms of chemical compound that identified from avocado peel to study the rules of the fragmentation reaction that occurs Sample analysis was examined using Gas Chromatography-Mass Spectrometry (GC-MS) with ionization Electron Impact (EI). Two compounds foun in avocado peel are 1,2,4-trihidroksiheptadek-12,16-diyne and 1,2,4-trihidroksiheptadek-16-yne-18-ene following the principle of even electron positive (EE+) which tends to always form even electron positive (EE+) and even electron neutral (EE0). The fragmentation mechanisms in both compounds are σ bond dissociation reaction and i cleavage which forms even electron positive (EE+) and even electron neutral (EE0). The fragmentation mechanism of the compounds in avocado peel can be estimated through interpretation of GC-MS mass spectra with base peak m/z 87. Keywords : Persea americana Mill.; GC-MS; fragmentation; 1,2,4-trihidroksiheptadek-12,16-diyne; 1,2,4-trihidroksiheptadek-16-yne-18-ene ABSTRAKPenyidikan struktur ion-ion fragment serta reaksi fragmentasinya sangat penting dan perlu dilakukan untuk dapat merekonstruksi kembali struktur kimia sampel yang diperiksa. Oleh karena itu, perlu diketahui mekanisme fragmentasi senyawa kimia yang diidentifikasi dari sampel kulit buah alpukat untuk mengetahui kaidah reaksi fragmentasi yang terjadi. Analisis sampel dilakukan menggunakan Gas-Chromatography-Mass Spectrometry (GC-MS) dengan cara ionisasi Electron Impact (EI). Dua senyawa yang terkandung dalam kulit buah alpukat yaitu senyawa 1,2,4-trihidroksiheptadek-12,16-diena dan senyawa 1,2,4-trihidroksiheptadek-16-ena-18-una mengikuti kaidah fragmentasi ion elektron genap positif (EE+) cenderung untuk selalu membentuk ion elektron genap positif (EE+) dan molekul elektron genap netral (EE0). Mekanisme fragmentasi pada kedua senyawa tersebut terjadi melalui reaksi dissosiasi ikatan σ dan reaksi pemutusan induktif membentuk ion elektron genap positif (EE+) dan molekul elektron genap netral (EE0). Mekanisme fragmentasi senyawa dalam kulit buah alpukat dapat diperkirakan melalui interpretasi spektrum massa GC-MS dengan base peak m/z 87. Kata kunci: Persea americana Mill.; GC-MS; fragmentasi; 1,2,4-trihidroksiheptadek-12,16-diena; 1,2,4-trihidroksiheptadek-16-ena-18-una

Alkyne-Forming Furan Fragmentation: A General Method to Convert Furans into Alkynoic Acids

Furans are readily available and highly reactive heterocycles that serve as versatile four-carbon synthons in organic synthesis. Recently, we discovered that furans, upon oxidation with singlet oxygen, can be transformed into alkynes via dual C–C double-bond cleavage. This Synpacts article presents an overview of the historical context and the development of this furan fragmentation reaction. We also discuss its application in natural product synthesis and a plausible reaction mechanism.1 Introduction2 Background of Alkyne-Forming Furan Fragmentation3 Reaction Development4 Conclusion

A copper-catalyzed radical coupling/fragmentation reaction: efficient access to β-oxophosphine oxides

The development of a novel copper-catalyzed three-component radical coupling/fragmentation cascade reaction to generate diverse β-oxophosphine oxides is reported.

First radioactive beams at ACCULINNA-2 facility and first proposed experiment

New fragment separator ACCULINNA-2 was installed at the primary beam line of the U-400M cyclotron in 2016. Recently, first radioactive ion beams were obtained. The design parameters of new facility were experimentally confirmed. Intensity, purity and transverse profile of several secondary beams at the final focal plane were studied. The intensities obtained for the secondary beams of 14B, 12Be, 9;11Li, 6;8He in the fragmentation reaction 15N (49.7 AMeV) + Be (2 mm) are in average 15 times higher in comparison to the ones produced at its forerunner ACCULINNA separator. The ACCULINNA-2 separator will become a backbone facility at the FLNR for the research in the field of light exotic nuclei in the vicinity of the nuclear drip lines. The planned first experiment, aimed for the observation of the 7H nucleus at ACCULINNA-2, is outlined.