Novel copolymers of styrene. 15. Halogen ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates

Novel halogen ring-disubstituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C3H7 (where R is 2-fluoro-5-methyl, 3-iodo-4-methoxy, 5-iodo-2-methoxy, 3,5-dichloro, 3,4-difluoro, 3,5-difluoro, 2-chloro-4-fluoro, 2-chloro-6-fluoro, 3-chloro-2-fluoro, and 3-chloro-4-fluoro) were prepared and copolymerized with styrene. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-disubstituted benzaldehydes and propyl cyanoacetate, and characterized by CHN elemental analysis, IR, 1H- and 13C-NMR. All the propenoates were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR, GPC, DSC, and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500ºC range with residue (1-3% wt.), which then decomposed in the 500-800ºC range.

Novel copolymers of vinyl acetate. 4. Halogen ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates

Novel copolymers of vinyl acetate and halogen ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C2H5 (where R is 2-Br, 3-Br, 4-Br, 2-Cl, 3-Cl, 4-Cl, 2-F, 3-F, 4-F, 2,3-dichloro, 2,4-dichloro, 2,6-dichloro, 3,4-dichloro, 2,4-difluoro, 2-bromo-3,4-dimethoxy) were prepared in solution with radical initiation at 70C. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of halogen ring-substituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C-NMR. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H and 13C-NMR. Thermal behavior of the copolymers was studied by DSC (Tg) and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 159-500ºC range with residue (8.8-15.2 wt%), which then decomposed in the 500-650ºC range.

OH and HO₂ radicals chemistry at a suburban site during the EXPLORE-YRD campaign in 2018

The first OH and HO2 radical observation in Yangtze River Delta, one of the four major urban agglomerations in China, was carried out at a suburban site Taizhou in summer 2018 from May to June, aiming to elucidate the atmospheric oxidation capacity in this region. The maximum diurnal averaged OH and HO2 concentrations were 1.0 × 107 cm−3 and 1.1 × 109 cm−3, respectively, which were the second highest HOx (sum of OH and HO2) radical concentrations observed in China. HONO photolysis was the dominant radical primary source, accounting for 42 % of the total radical initiation rate. Other contributions were from carbonyl photolysis (including HCHO, 24 %), O3 photolysis (17 %), alkenes ozonolysis (14 %), and NO3 oxidation (3 %). A chemical box model based on RACM2-LIM1 mechanism could generally reproduce the observed HOx radicals, but systematic discrepancy remained in the afternoon for OH radical, when NO mixing ratio was less than 0.3 ppb. Additional recycling mechanism equivalent to 100 ppt NO was capable to fill the gap. The sum of monoterpenes was on average up to 0.4 ppb during daytime, which was allocated all to α-pinene in the base model. Sensitivity test without monoterpene input showed the modelled OH and HO2 concentrations would increase by 7 % and 4 %, respectively, but modelled RO2 concentration would significantly decrease by 23 %, indicating that monoterpene was an important precursor of RO2 radicals in this study. Consequently, the daily integrated net ozone production would reduce by 6.3 ppb if without monoterpene input, proving the significant role of monoterpene on the photochemical O3 production in this study. Besides, the generally good agreement between observed and modelled HOx concentrations suggested no significant HO2 heterogeneous uptake process during this campaign. Incorporation of HO2 heterogeneous uptake process would worsen the agreement between HOx radical observation and simulation, and the discrepancy would be beyond the measurement-model combined uncertainties using an effective uptake coefficient of 0.2. Finally, the ozone production efficiency (OPE) was only 1.7 in this study, a few folds lower than other studies in (sub)urban environments. The low OPE indicated slow radical propagation rate and short chain length. As a consequence, ozone formation was suppressed by the low NO concentration in this study.

Novel copolymers of vinyl acetate. 3 Ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates

Novel copolymers of vinyl acetate and ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C2H5 (where R is 4-acetoxy, 4-acetamido, 2-cyano, 3-cyano, 4-cyano, 4-dimethylamino, 4-diethylamino, 2,4,6-trimethyl, 2,3-dimethyl-4-methoxy, 2,4-dimethoxy-3-methyl were prepared in solution with radical initiation at 70C. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C-NMR. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H and 13C-NMR. Thermal behavior of the copolymers was studied by DSC (Tg) and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 160-350ºC range with residue (1.5-15.1 wt%), which then decomposed in the 500-650ºC range.

In situ polymerization monitoring of a diacrylate in an electrically conducting mesoporous nanoparticle scaffold

The properties of nanoparticle–polymer composites strongly depend on the network structure of the polymer matrix. By introducing nanoparticles into a monomer (solution) and subsequently polymerizing it, the formation of the polymer phase influences the mechanical and physicochemical properties of the composite. In this study, semi-conducting indium tin oxide (ITO) nanoparticles were prepared to form a rigid nanoparticle scaffold in which 1,6-hexanediol diacrylate (HDDA), together with an initiator for photo-polymerization, was infiltrated and subsequently polymerized by UV light. During this process, the polymerization reaction was characterized using rapid scan Kubelka–Munk FT-IR spectroscopy and compared to bulk HDDA. The conductivity change of the ITO nanoparticles was monitored and correlated with the polymerization process. It was revealed that the reaction rates of the radical initiation and chain propagation are reduced when cured inside the voids of the nanoparticle scaffold. The degree of conversion is lower for HDDA infiltrated into the mesoporous ITO nanoparticle scaffold compared to purely bulk-polymerized HDDA. Graphical abstract

Using Enzymes to Tame Nitrogen-Centered Radicals for Enantioselective Hydroamination

The construction of C–N bonds is essential for the preparation of numerous molecules critical to modern society1,2. Nature has evolved enzymes to facilitate these transformations using nucleophilic and nitrene transfer mechanisms3,4. However, neither natural nor engineered enzymes are known to generate and control nitrogen-centered radicals, which serve as valuable species for C–N bond formation. Herein, we describe a platform for generating nitrogen-centered radicals within protein active sites, thus enabling asymmetric hydroamination reactions. Using flavin- dependent ‘ene’-reductases with an exogenous photoredox catalyst, amidyl radicals are generated selectively within the protein active site. Empowered by directed evolution, these enzymes are engineered to catalyze 5-exo, 6-endo, 7-endo, 8-endo, and intermolecular hydroamination reactions with high levels of enantioselectivity. Mechanistic studies suggest that radical initiation occurs via an enzyme-gated mechanism, where the protein thermodynamically activates the substrate for reduction by the photocatalyst. Molecular dynamics studies suggest that the enzymes bind substrates using non-canonical binding interactions, which may serve as a handle to further manipulate reactivity. This approach demonstrates the versatility of these enzymes for controlling the reactivity of high-energy radical intermediates and highlight the opportunity for synergistic catalyst strategies to unlock new enzymatic functions.

Novel copolymers of vinyl acetate. 2. Oxy ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates

Novel copolymers of vinyl acetate and oxy ring-substituted ethyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO2C2H5 (where R is 2-methoxy, 3-methoxy, 4-methoxy, 2-ethoxy, 4-ethoxy, 4-propoxy, 4-butoxy, 2,3-dimethoxy, 2,4-dimethoxy, 2,5-dimethoxy, 3,4-dimethoxy, 2,3,4-trimethoxy, 2,4,5-trimethoxy, 2,4,6-trimethoxy, 3,4,5-trimethoxy) were prepared in solution with radical initiation at 70C. The propenoates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and ethyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C-NMR. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H and 13C-NMR. Thermal behavior of the copolymers was studied by DSC (Tg) and TGA. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 160-350ºC range with residue (2.2-25.3 wt%), which then decomposed in the 500-650ºC range.

Synthesis and styrene copolymerization of novel phenoxy and benzyloxy ring-substituted tert-butyl phenylcyanoacrylates

Novel phenoxy and benzyloxy ring-substituted tert-butyl phenylcyanoacrylates, RPhCH=C(CN)CO2C(CH3)3 (where R is 3-phenoxy, 3-(4-chlorophenoxy), 3-(4-methoxyphenoxy), 3-(4-methylphenoxy), 2-benzyloxy, 3-benzyloxy) were prepared and copolymerized with styrene. The acrylates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and tret-butyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C NMR. All the ethylenes were copolymerized with styrene in solution with radical initiation at 70C. The compositions of the copolymers were calculated from nitrogen analysis.

Flash C-H Chlorination of Ethylene Carbonate Using a New Photoflow Setup

We report flash C-H chlorination of ethylene carbonate, which gives chloroethylene carbonate, a precursor to ethylene carbonate. A novel photoflow setup designed for a gas-liquid biphasic reaction turned out to be useful for the direct use of chlorine gas in flow. The setup employed sloped channels so as to make the liquid phase thinner, ensuring high surface to volume ratio. When ethylene carbonate was introduced to the reactor, the residence time was measured to be 15 or 30 sec, depending on the slope of the reactor to be 15 or 5 °C, respectively. Such short time exposition sufficed the photo C-H chlorination. The partial irradiation of the flow channels sufficed for the C-H chlorination, which is consistent with the requirement of photoirradiation for the purpose of radical initiation. We also found that the contaminated water negatively influenced the performance of C-H chlorination. The 100% selectivity for single chlorination required the low conversion of ethylene carbonate such as 9%, which was controlled by limited introduction of chlorine gas. At a higher conversion of ethylene carbonate such as 63%, the selectivity for mono-chlorinated ethylene carbonate over di-chlorinated ethylene carbonate was 86%. We found that the contaminated water negatively influenced the performance of the C-H chlorination.

Synthesis and styrene copolymerization of novel alkyl ring-substituted t-butyl phenylcyanoacrylates

Novel alkyl ring-substituted t-butyl phenylcyanoacrylates, RPhCH=C(CN)CO2C(CH3)3 (where R is H, 2-methyl, 3-methyl, 4-methyl, 2-ethyl, 4-ethyl, 4-propyl, 4-i-propyl, 4-butyl, 4-i-butyl) were prepared and copolymerized with styrene. The acrylates were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and t-butyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C NMR. All the ethylenes were copolymerized with styrene in solution with radical initiation (ABCN) at 70C. The compositions of the copolymers were calculated from nitrogen analysis.