Atomistic chemical computation of Olefin polymerization reaction catalyzed by (pyridylamido)hafnium(IV) complex: Application of Red Moon simulation

We have realized the microscopic simulation of olefin polymerization, that is, the simulation of the catalytic polymerization (CP) reaction system composed of (pyridylamido)hafnium(IV) complex as the catalyst. For this purpose, we adopted Red Moon (RM) method, a novel molecular simulation method to simulate the complex reaction system. First, according to the previous research, with the help of the QM calculation, we proposed a model system and elementary processes and explained the theoretical treatment of the simulation by the RM method (the RM simulation). In addition, we also proposed a macroscopic simulation based on chemical kinetics simulation. Then, we performed two simulations and compared them in terms of the effective time evolution of the three macroscopic physical quantities, the number-average molecular weight M_n , the mass-average molecular weight M_w , and the molar-mass dispersity Đ_M . The comparison showed that the two simulations are in quantitative or partially qualitative agreement with each other. Therefore, it is concluded that the RM simulation could not only simulate the CP reaction process microscopically, but also it is connected essentially to reproduce the time evolution of the macroscopic physical quantities on the basis of its microscopic simulation data. © 2018 Wiley Periodicals, Inc.     

Fused silica capillary tube isotachophoresis using a multichannel photodiode array detector

Isotachophoresis carried out in a 0.25 mm i.d. fused-silica capillary tube yielded high resolution, compared with that in a fluorinated ethylene-propylene polymer tube. The use of an ultraviolet-visible multichannel spectrophotometer with photodiode array as detector together with a cross flow cell (volume 0.01 μl) was investigated. The system was successfully applied to the analysis of cationic dyes such as neutral red, bismarck brown, and basic fuchsine.     

The development of an automated continuous measurement system for the monitoring of HCHO and CH3CHO in the atmosphere by using an annular diffusion scrubber coupled to HPLC

An automated continuous measurement system for the monitoring of formaldehyde (HCHO) and acetaldehyde (CH₃CHO) in the urban atmosphere was developed by using an annular diffusion scrubber in conjunction with a high-performance liquid chromatograph (HPLC). With this technique, atmospheric HCHO and CH₃CHO were effectively collected by the annular diffusion scrubber which consists of a porous polytetrafluoroethylene (PTFE) tube disposed concentrically within a Pyrex-glass tube and a scrubbing solution. 2,4-Dinitrophenylhydrazine (DNPH) was selected as the scrubbing solution for collecting HCHO and CH₃CHO, which are derivatized to 2,4-dinitrophenylhydrazone-formaldehyde (DNPH-HCHO) and 2,4-dinitrophenylhydrazone-acetaldehyde (DNPH-CH₃CHO), respectively. An aliquot of the sample solution was automatically injected into an HPLC equipped with a semi-micro ODS column and a UV-VIS detector for separating and determining DNPH-HCHO and DNPH-CH₃CHO. All the operations are sequenced by a programmable controller, and automated continuous measurements are performed with a typical temporal resolution of 1 h. The collection efficiencies of HCHO and CH₃CHO were about 97% and 93%, respectively, at an air flow rate of 0.2 L/min. The lower detection limits (3σ of the blank hydrazones) of HCHO and CH₃CHO were 0.05 ppbv and 0.10 ppbv, respectively, in the case of 12-L air sample volume. Analytical response of a standard solution of DNPH-HCHO and DNPH-CH₃CHO by the HPLC during a 10-day continuous measurement was unchanged and the relative standard deviation (RSD) was < 1.0%. Interferences from O₃ and NO₂ were insignificant in this annular diffusion scrubber method. Both for HCHO and CH₃CHO measurements, concentrations from this developed system well agreed with those measured by a DNPH Silica cartridge method.     

Copper(I) Complexes with a Proximal Aromatic Ring: Novel Copper–Indole Bonding

A unique bonding of indole to a metal ion has been established. Two new tridentate N ligands with a pendent indole ring gave Cu^I complexes 1 and 2 , the latter of which exhibits the new form of bonding between the Cu^I ion in a distorted tetrahedral geometry and the indole C(2)−C(3) moiety. The bond is dependent upon the length of the side chain and therefore the accessibility of the ring to the metal center.     

Polyacrylamides as hydrophilic selectors in non-aqueous capillary electrophoresis

Polyacrylamides (PAAms) were investigated as hydrophilic selectors in non-aqueous capillary electrophoresis (CE). Separation of 10 substituted benzoates and unsubstituted benzoate as model samples was greatly improved by the addition of PAAms in acetonitrile-CE. The migration behavior indicates that the carbonyl moiety of PAAms works as a good hydrogen-accepting site toward hydrogen-donating analytes such as 4-hydroxybenzoate anion (4OH-BA) in acetonitrile. PAAms also serve as electron-accepting agents with its amide proton interacting with the dissociated carboxyl groups of the benzoates. The ion-dipole interaction is useful to control the migration behavior of benzoates without hydrogen-donating substituents. The overall mode of the interaction is similar to that of polyethylene glycol (PEG) 20000 reported previously, but the complex formation constant of poly(N-tert.-butyl)acrylamide (PBAAm) with 40H-BA estimated here was 130-fold larger than that of PEG 20000. This would be ascribed to the strong basicity of the carbonyl oxygen atoms of PBAAm as compared with the ether oxygen atoms of PEG. Furthermore, a copolymer of (N-tert.-butyl)acrylamide-acrylamide [70:30 (in feed)] exhibited a complex formation constant of about fourfold larger toward 4OH-BA than PBAAm, most probably due to decrease in steric hindrance from the tert.-butyl groups. Adrenaline and its six precursors have been separated successfully using the PAAms.     

A double-functionalized cyclen with carbamoyl and dansyl groups (cyclen = 1,4,7,10-tetraazacyclododecane): a selective fluorescent probe for Y(3+) and La(3+).

A cyclen (=1,4,7,10-tetraazacyclododecane) doubly functionalized with three carbamoylmethyl groups and one dansylaminoethyl (dansyl = 2-(5-(dimethylamino)-1-naphthalenesulfonyl) group (L(2) = 1-(2-(5-(dimethylamino)-1-naphthalenesulfonylamido)ethyl)-4,7,10-tris(carbamoylmethyl)-cyclen) was synthesized and characterized. Potentiometrtic pH titration and UV spectrophotometric titration of L(2) served to determine deprotonation of the pendant dansylamide (L(2) --> H(-1)L(2)) with a pK(a) value of 10.6, while the fluorometric titration disclosed a pK(a) value of 8.8 +/- 0.2, which was assigned to the dansyl deprotonation in the excited state. The 1:1 M(3+)-H(-1)L(2) complexation constants (log K(app) = 6.0 for Y(3+) and 5.2 for La(3+), where K(app)(M-H(-1)L(2)) = [M(3+)-H(-1)L(2)]/[M(3+)](free)[L(2)](free) (M(-1)) at pH 7.4) were determined by potentiometric pH titration and UV and fluorescence spectrophotometric titrations (excitation at 335 nm and emission at 520 nm) in aqueous solution (with I = 0.1 (NaNO(3))) and 25 degrees C. The X-ray structure analysis of the Y(3+)-H(-1)L complex showed nine-coordinated Y(3+) with four nitrogens of cyclen, three carbamoyl oxygens, and the deprotonated nitrogen and a sulfonyl oxygen of the dansylamide. The crystal data are as follow: formula C(28)H(49)N(11)O(13.5)SY (Y(3+)-H(-1)L(2) x 2(NO(3)(-)) x 2.5H(2)O), M(r) = 876.73, monoclinic, space group P2(1)/n (No. 14), a = 18.912(3) A, b = 17.042(3) A, c = 24.318(4) A, beta = 95.99(1) degrees, V = 7794(2) A(3), Z = 8, R1 = 0.099. Upon M(3+)-H(-1)L(2) complexation, the dansyl fluorescence greatly increased (8.6 and 3.8 times for Y(3+) and La(3+), respectively) in aqueous solution at pH 7.4. Other lanthanide ions also yielded Ln(3+)-H(-1)L(2) complexes with similar K(app) values, although all the dansyl fluorescences were weakly quenched. On the other hand, zinc(II) formed only a 1:1 Zn(2+)-L(2) complex at neutral pH with negligible fluorescence change. The X-ray crystal structure of the Zn(2+)-L(2) complex confirmed the pendant dansylamide being noncoordinating. The crystal data are as follow: formula C(28)H(51)N(11)O(14)SZn (Zn(2+)-L(2) x 2(NO(3)(-)) x 3H(2)O), M(r) = 863.22, monoclinic, space group C2/n (No. 15), a = 35.361(1) A, b = 13.7298(5) A, c = 18.5998(6) A, beta = 119.073(2) degrees, V = 7892.3(5) A(3), Z = 8, R1 = 0.084. Other divalent metal ions did not interact with L(2) at all (e.g., Mg(2+) and Ca(2+)) or interacted with L(2) with the dansyl fluorescence quenched (e.g., Cu(2+)).     

Regio-selective cyanation of (Z)-(1,2-dibromo-2-arylvinyl)triisopropylsilane with suppression of halogen elimination

Highly regio-selective cyanation of vicinal (Z)-dibromoalkenyl silanes was achieved by a vinylic Rosenmund-von Braun reaction, significantly suppressing side-production of alkyne. The alkyne was generated by a halogen elimination side-reaction that is an intrinsic problem in metal-activation of vicinal dihaloalkenes. We have studied to overcome the problem, and finally found the combination of CuCN and O = PPh₃ in toluene solvent effectively controlled the production of byproducts. The resultant single isomer has significance in potentially application as a multi-tunable synthetic scaffold.     

Hydrogen Peroxide Formation by Electric Discharge with Fine Bubbles

Pulsed discharge plasma is typical oxidation technology for disposing organic compounds in aqueous solutions. When this electrical discharge plasma was applied in water, it may produce hydrogen peroxide (H₂O₂) without any catalyst or chemical agent. In order to increase H₂O₂ production by electrical discharge plasma in water, fine bubbles were introduced into the electrical discharge plasma in this experiment. Bipolar pulsed voltages were applied to cylindrical electrodes in the water while Ar or O₂ bubbles were introduced, generating a pulsed discharge plasma. The introduction of the bubbles seemed to enhance the dissociation of water molecules and increased H₂O₂ formation, especially with O₂ bubbling. Dissolved oxygen in the water contributed to H₂O₂ formation by pulsed discharge plasma with the bubbles, while dissociation of water molecules was the cause of H₂O₂ formation by pulsed discharge plasma without bubbles. More H₂O₂ was formed by pulsed discharge plasma with O₂ bubbles, because the amount of dissolved oxygen in the water increased upon bubbling with O₂.     

Structure of amipurimycin,a nucleoside antibiotic having a novel branched sugar moiety

Structure of amipurimycin was determined chemically to be $\text{1}$.