Syntheses and Studies of PEG-b-PNIPA Block Polymers

ＳｙｎｔｈｅｓｅｓａｎｄＳｔｕｄｉｅｓｏｆＰＥＧ┐ｂ┐ＰＮＩＰＡＢｌｏｃｋＰｏｌｙｍｅｒｓＣＡＯＷｅｉ－ｘｉａｏ＊＊ａｎｄＺＨＡＮＧＴａｏ（ＣｏｌｅｇｅｏｆＣｈｅｍｉｓｔｒｙａｎｄＭｏｌｅｃｕｌａｒＥｎｇｉｎｅｒｉｎｇ，ＰｅｋｉｎｇＵｎｉｖｅｒｓｉｔ...     

Determination of Cd,Pb and Sr by Microwave Plasma Torch Atomic Emision Spectrometry Using an Electrothermal Vaporization Sample Introduction System

ＩｎｔｒｏｄｕｃｔｉｏｎＥｌｅｔｒｏｔｈｅｒｍａｌｖａｐｏｒｉｚａｔｉｏｎ（ＥＴＶ）ａｓａｍｅａｎｓｏｆｓａｍｐｌｅｉｎｔｒｏｄｕｃｔｉｏｎｉｎｍｉｃｒｏｗａｖｅｉｎ－ｄｕｃｅｄｐｌａｓｍａ（ＭＩＰ）ｓｏｕｒｃｅｓｐｅｃｔｒｏｍｅｔｒｙｈａｓｂｅｅｎ...     

C_(19)-DITERPENOID ALKALOIDS OF DELPHINIUM MOLLIPILUM

Ｃ_（１９）－ＤＩＴＥＲＰＥＮＯＩＤＡＬＫＡＬＯＩＤＳＯＦＤＥＬＰＨＩＮＩＵＭＭＯＬＬＩＰＩＬＵＭ￥ＳｕｏＭｉｎｇＺＨＡＮＧ；ＱｉｎｇＹｕＯｕ（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＣｈｅｍｉｃａｌＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉ?..     

Preparation of Unsupported Molybdenum Phosphide Hydrofining Catalysts

ＨｙｄｒｏｆｉｎｉｎｇｃａｔａｌｙｓｔｓｃｏｎｔａｉｎＭｎ Ｎｉ,Ｎｉ Ｍｏ ,Ｎｉ Ｗ ,Ｃｏ Ｍｏ ,Ｍｏ ,Ｗ ,Ｎｉ,Ｃｏ ,ｅｔｃａｎｄｍａｎｙｓｔｕｄｉｅｓｏｆｔｈｅｓｅｃａｔａｌｙｓｔｓａｒｅｃｏｎｃｅｒｎｅｄｗｉｔｈｔｈｅａｄ ｄｉｔｉｏｎｏｆｐｈｏｓｐｈｏｒｕｓｏｒｃｏｍｐｏｕｎｄｓｃｏｎｔａｉｎｉｎｇｐｈｏｓ ｐｈｏｒｕｓｔｏｇｉｖｅＮｉ Ｍｏ Ｐ ,Ｗ Ｎｉ Ｐ ,Ｍｏ Ｐ ,Ｎｉ Ｐ ,Ｗ Ｐ ,Ｃｏ Ｍｏ Ｐ ,ＮｉＰＳ3,ａｎｄＭｏ Ｎｉ Ｗ Ｐ[1 ,2 ] .Ｔｈｅｅｆ ｆｅｃｔｏｆａｄｄｉｎｇｐｈｏｓｐｈｏｒｕｓｏｒ…     

SEMI-SYNTHESIS OF TRIPTONIDE

ＳＥＭＩ－ＳＹＮＴＨＥＳＩＳＯＦＴＲＩＰＴＯＮＩＤＥ￥ＰｅｎｇＣｈｅｎｇＭＡａｎｄＷｅｉＹＡＮ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａＭｅｄｉｃａ，ＩｎｓｔｉｔｕｔｅｏｆＤｅｒｍａｔｏｌｏｇｙ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＭｅｄｉｃａｌＳｃｉｅｎ...     

Kinetic model of living ionic polymerization with three active species

Ｌｉｖｉｎｇｉｏｎｉｃｐｏｌｙｍｅｒｉｚａｔｉｏｎｕｓｕａｌｌｙｉｎｖｏｌｖｅｓｓｅｖｅｒａｌｃｏｅｘｉｓｔｉｎｇｓｐｅｃｉｅｓｏｆｄｉｆｆｅｒｅｎｔｒｅａｃｔｉｖｉｔｉｅｓ,ｓｕｃｈａｓｃｏｎｔａｃｔｉｏｎｐａｉｒｓ,ｓｏｌｖｅｎｔｓｅｐａｒａｔｅｄｉｏｎｐａｉｒｓａｎｄｆｒｅｅａｎｉｏｎｓ,ｗｈｉｃｈａｒｅｉｎｄｙｎａｍｉｃｅｑｉｌｌｉｂｒｉａ.Ｔｈｅｒｅａｃｔｉｏｎｓｃｈｅｍｅｒｅａｄｓ[1,2]ａｓｓｃｈｅｍｅ1.Ｐ-ｉ,Ｍ+ｉ+ｎＳ　ｋｓ　　ｋｃ　Ｐ-ｉ,Ｓｎ,Ｍ+ｔ　ｋｄ　　ｋａ　Ｐ-ｉ+Ｍ+ｉ,Ｓｎ+Ｍｋ…     

Catalytic Spectrophotometric Determination of Ultratrace Amounts of Silver with Solubilizing Effect of Nonionic Surfactant

ＩｎｔｒｏｄｕｃｔｉｏｎＴｒｉａｚｅｎｅｒｅａｇｅｎｔｓａｒｅｉｎｔｅｒｅｓｔｉｎｇｂｅｃａｕｓｅｏｆｔｈｅｉｒｓｔｒｏｎｇｃｏｍｐｌｅｘａｔｉｏｎａｂｉｌｉｔｉｅｓｗｉｔｈｔｒａｎｓｉｔｉｏｎｍｅｔａｌｓ .1 6Ｈｏｗｅｖｅｒ,ｌｉｔｔｌｅｄｅｃｏｌｏｒａｔｉｏｎｏｆｔｈｅｍｃａｔａｌｙｚｅｄｂｙｓｉｌｖｅｒｉｏｎｈａｓｂｅｅｎｓｔｕｄｉｅｄｉｎａｎａｌｙｔｉｃａｌｃｈｅｍｉｓｔｒｙ .Ｍａｎｙａｎａｌ ｙｓｉｓｔｓｈａｖｅｒｅｐｏｒｔｅｄｔｈｅｕｓｅｏｆｃａｔａｌｙｔｉｃｒｅａｃｔｉｏｎｓｆｏｒｔ…     

Microcalorimetric Study of the Biological Effects of Zn~(2+) on Bacillus thuringiensis Growth

ＩｎｔｒｏｄｕｃｔｉｏｎＣａｌｏｒｉｍｅｔｒｙｈａｓｂｅｅｎｕｓｅｄｉｎｍｏｎｉｔｏｒｉｎｇｃｅｌｌｕｌａｒｍｅｔａｂｏｌｉｓｍｂｙｍｅａｎｓｏｆｈｅａｔｍｅａｓｕｒｅｍｅｎｔｓ ,ｅｓｐｅｃｉａｌｌｙｉｎｓｔｕｄｙｉｎｇｍｅｔａｂｏｌｉｓｍｉｎｃｅｌｌｓａｎｄｗｈｏｌｅｏｒｇａｎｉｓｍ .1,2 Ｍｉ ｃｒｏｃａｌｏｒｉｍｅｔｒｙｉｓａｌｓｏｕｓｅｄｉｎｍｅａｓｕｒｉｎｇｔｈｅｅｆｆｅｃｔｓｏｆｖａｒ ｉｏｕｓｓｕｂｓｔａｎｃｅｓａｎｄｃｕｌｔｕｒｅｃｏｎｄｉｔｉｏｎｓｏｎｍｅｔａｂｏｌｉｓｍ .Ｍｉｌｅ…     

Studies on Synthesis and Intramolecular Catalyzed Hydrolysis of Thiophosphoramidate Derivatives of Nucleoside

ＩｎｔｒｏｄｕｃｔｉｏｎＮｕｃｌｅｏｓｉｄｅｓａｎｄｔｈｅｉｒａｎａｌｏｇｕｅｓａｓｐｏｔｅｎｔｉａｌａｎｔｉ ｃａｎｃｅｒａｎｄａｎｔｉｖｉｒｕｓａｇｅｎｔｓｈａｖｅｂｅｅｎｓｔｕｄｉｅｄｅｘｔｅｎｓｉｖｅｌｙ .Ｍｏｓｔｏｆｔｈｅｃｕｒｒｅｎｔｌｙｌｉｃｅｎｓｅｄａｎｔｉｖｉｒａｌｄｒｕｇｓａｎｄｍａｎｙｏｆｔｈｅｄｒｕｇｓｕｓｅｄｉｎａｎｔｉｃａｎｃｅｒｃｈｅｍｏｔｈｅｒａｐｙａｒｅｎｕｃｌｅｏｓｉｄｅａｎａｌｏｇｕｅｓ .1Ｆｏｒｔｈｅｍａｊｏｒｉｔｙｏｆｔｈｅｓｅａｎａｌｏｇｕｅｓｓｈｏｗｎ…     

Mechanism of the Deaquation of Aquopentaaminocobalt(III) Bromide

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｏｌｉｄ ｐｈａｓｅｄｅａｑｕａｔｉｏｎ ａｎａｔｉｏｎｒｅａｃｔｉｏｎ[Ｍ(ＮＨ3 ) 5(Ｈ2 Ｏ) ]Ｘ3 → [Ｍ(ＮＨ3 ) 5Ｘ]Ｘ2 +Ｈ2 Ｏ(Ｍ =Ｃｏ3 + ,Ｃｒ3 + ｏｒＲｕ3 + ａｎｄＸ =Ｃｌ- ,Ｂｒ- ｏｒＮＣＳ- )ｈａｓｂｅｅｎｗｉｄｅｌｙｓｔｕｄｉｅｄｓｉｎｃｅｔｈｅｎｉｎｅｔｅｅｎｓｉｘｔｉｅｓ .Ｔｈｅｔｈｅｒｍａｌａｎｄｋｉｎｅｔｉｃｐａｒａｍｅｔｅｒｓｈａｖｅｂｅｅｎｃａｌｃｕｌａｔｅｄａｎｄｔｈｅｄｉｆｆｅｒｅｎｔｍｅｃｈａｎｉｓｍｈａｓｂｅｅｎｐｒｏｐｏｓｅｄａｎｄｄ…     

白杨素在汞电极上的电化学行为及其消除超氧阴离子自由基能力研究

The electrochemical behavior of chrysin in pH 2.0-9.0 Britton-Robinson （B-R） buffer solutions was studied by the means of linear sweep voltammetry and cyclic voltammetry at a static mercury drop electrode. In different pH range of B-R buffer solutions, chrysin could cause four reduction waves. In pH 2.0-5.8 B-R buffer solutions, wave P1 yielded by chrysin is a one-electron reduction wave, and wave P1 caused by further reduction of the products of wave P1 in pH〈3.0 B-R buffer solution is also a one-electron reduction wave. But in 3.0〈pH〈5.8 B-R buffer solution wave P1 was overlapped by the hydrogen wave. Between pH 5.8 and 9.0, chrysin could yield two reduction waves P2 and P3- The former is an irreversible adsorptive wave of ionized chrysin involving one electron and the latter is also an irreversible adsorptive wave of reduction intermediate radical of chrysin involving one electron and one proton. And a linear relationship between ip3 and the concentration of chrysin can be established from 1.0×10^-6 to 4.0×10^-5 mol·L^-1 （r=0.9924） with the detection limit of 5×10^-7 mol·L^-1. In addition, the antioxidant ability of chrysin was investigated by linear sweep voltammetry （LSV）. The determination result of IC50 of chrysin showed that chrysin is a good antioxidant.     

Competition between thermal decomposition and hydrolysis of 2,2'-azobis(2-amidinopropane) in aqueous solution

The thermal decomposition and hydrolysis of 2,2′-azobis(2-amidinopropane) were examined as functions of pH. The rate of decomposition decreased with increasing pH. The specific rates at 60°C were 3.85 × 10^?5 1/sec at pH 0.90 and 2.5 × 10^?5 1 see at pH ≥ 8.5. The hydrolysis in alkaline solution yielded 2,2′-azobis(2-carbamylpropane) which was stable to thermal decomposition. The relation between the specific rate of hydrolysis k_h′ and the concentration of hydroxyl ion was obtained as k_h′ = 4.0 × 10^?2 [OH]^0.50 1/sec at 60°C. In alkaline solution, the rate of hydrolysis was considerably larger than that of thermal decomposition. A mechanism for this hydrolysis is propesed.     

Study of Activation and Inhibition of Certain Metal Ions to Amylase Catalyzed Reaction by Microcalorimetry

IntroductionMostcomplicatedreactionshappenedinlivingcrea tures ,amongthemenzymecatalyzedreactionisanimpor tantclass .Itissignificantinboththeoryandpracticetoinvestigateenzymecatalyzedreaction .Therearemanyex perimentalmethodssuchasspectrophotometry ,titrimetry ,isotopemethod ,microcalorimetryandsoon ,inwhichmi crocalorimetryisanewoneduetoitshighsensitivityandaccuracy .Wecanstudythewholeprocessoftheheatef fectusingamicrocalorimeter .Sincetheabsorptionorpro ductionofheatisanintrinsicpropertyofe…     

Kinetic evidence for the occurrence of general acid-base catalysis in N-methylhydroxylaminolysis of N-ethoxycarbonylphthalimide (NCPH)

Pseudo-first-order rate constants (k_{1 obs}) for the reaction of MeNHOH with NCPH obey the relationship: k_{1 obs}=k^′_b[MeNHOH]_T² where [MeNHOH]_T represents total concentration of N-methylhydroxylamine buffer. The rate constants, k_{1 obs} obtained at different total concentration of acetate buffer ([Buf]_T) in the presence of 0.004 mol dm⁻³ MeNHOH follow the relationship: k_{1 obs}=k_b[Buf]_T. The values of acetate buffer-catalyzed rate constant (k_b) at different pH reveal the occurrence of both general base- and general acid- or general base-specific acid-catalysis in the reaction of MeNHOH with NCPH. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 647–654, 1997.     

Easily available niobium(V) mixed chloro‐alkoxide complexes as catalytic precursors for ethylene polymerization

The dinuclear [NbCl_n(OR)_(5‐n)]₂ (n = 4, R = Et, 1 ; n = 4, R = CH₂Ph, 2 ; n = 3, R = Et, 3 ; n = 2, R = Et, 4 ; n = 2, R = , 5 ), and [Nb(OEt)₅]₂, 6 , and the mononuclear niobium compounds NbCl₄[κ²? OCH₂CH(R′)OR] (R = Me, R′ = H, 7 ; R = Et, R′ = H, 8 ; R = CH₂Cl, R′ = H, 9 ; R = CH₂CH₂OMe, R′ = H, 10 ; R = R′ = Me, 11 ), NbBr₄[κ²? OCH₂CH₂OMe], 12 , and NbCl₃(κ²? OCH₂CH₂OMe)(κ¹? OCH₂CH₂OMe), 13 , were tested in ethylene polymerization. Optimized reaction conditions included the use of D‐MAO as co‐catalyst and chlorobenzene as solvent at 50 °C. Complex 7 , whose X‐Ray structure is described here for the first time, exhibited the highest activity ever reported for a niobium catalyst in alkene polymerization [151 kg_polymer × mol_Nb^?1 × h^?1 × bar^?1]. Compounds 1 , 3‐5 , 8 , 13 showed activities similar to that of 7 . Linear polyethylenes (characterized by FT‐IR, NMR, GPC, and DSC analyses) with a broad polydispersivity were obtained. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and Characterization of Manganese(I) Carbonyl Complexes of the Type [(OC)4Mn{μ‐P(R)Aryl}]2

Metalation of secondary phosphanes HPRR′ [R = R′ = C₆H₄‐4‐Me, C₆H₃‐3,5‐Me₂ ( 3 ), C₆H₄‐4‐NMe₂ ( 4 ); R/R′ = Ph/cHex] with Mn₂(CO)₁₀ in boiling xylene (mixture of isomers), until the evolution of gaseous carbon monoxide ceases, leads to the formation of the dinuclear complexes of the type [(OC)₄Mn(μ‐PRR′)]₂ [R = R′ = C₆H₄‐4‐Me ( 5 ), C₆H₃‐3,5‐Me₂ ( 6 ), R/R′ = Ph/cHex ( 7 ), R = R′ = C₆H₄‐4‐NMe₂ ( 8 )] with poor to moderate yields. These manganese(I) complexes are only sparingly soluble or even nearly insoluble in hydrocarbons at room temperature. Planar four‐membered Mn₂P₂ rings represent the central moiety with four carbonyl ligands at each manganese(I) atom. The steric demand of the P‐bound substituents influences the Mn–P bond lengths as well as the P–Mn–P bond angles.     

Influence of Cu(II) Ions on the Mechanism of the Ring Transformation of S‐(2‐Oxotetrahydrofuran‐3‐yl)‐N‐(4‐methoxyphenyl)isothiouronium Bromide

The effect of additional Cu(II) ions on the rate of transformation of S‐(2‐oxotetrahydrofuran‐3‐yl)‐N‐(4‐methoxyphenyl)isothiouronium bromide ( 1 ) into 5‐(2‐hydroxyethyl)‐2‐[(4‐methoxyphenyl)imino]‐1,3‐thiazolidin‐4‐one ( 2 ) has been studied in aqueous buffer solutions. The reaction acceleration in acetate buffers is caused by the formation of a relatively weakly bonded complex (K_c = 600 L·mol^?1) of substrate with copper(II) acetate in which the Cu(II) ion acts as a Lewis acid coordinating the carbonyl oxygen and facilitating the intramolecular attack, leading to the formation of intermediate T^±. The formation of the complex of copper(II) acetate with free isothiourea in the fast preequilibrium (K_c) is followed by the rate‐limiting transformation (k_Cu) of this complex. At the high concentrations of the acetate anions, the reaction is retarded by the competitive reaction of these ions with copper(II) acetate to give an unreactive complex [Cu(OAc)₄]^2?_. The influence of Cu(II) ions on the stability of reaction intermediates and the leaving group ability of the alkoxide‐leaving group compared to the Cu(II)‐uncatalyzed reaction is also discussed.     

Ester Hydrolysis by a Cyclodextrin Dimer Catalyst with a Tridentate N,N′,N′′‐Zinc Linking Group

A new β‐cyclodextrin dimer, 2,6‐dimethylpyridine‐bridged‐bis(6‐monoammonio‐β‐cyclodextrin) (pyridyl BisCD, L), is synthesized. Its zinc complex (ZnL) is prepared, characterized, and applied as a catalyst for diester hydrolysis. The formation constant (log K_ML=7.31±0.04) of the complex and deprotonation constant (pK_a1=8.14±0.03, pK_a2=9.24±0.01) of the coordinated water molecule were determined by a potentiometric pH titration at (25±0.1)°C, indicating a tridentate N,N′,N′′‐zinc coordination. Hydrolysis kinetics of carboxylic acid esters were determined with bis(4‐nitrophenyl)carbonate (BNPC) and 4‐nitrophenyl acetate (NA) as the substrates. The resulting hydrolysis rate constants show that ZnL has a very high rate of catalysis for BNPC hydrolysis, yielding an 8.98×10³‐fold rate enhancement over uncatalyzed hydrolysis at pH 7.00, compared to only a 71.76‐fold rate enhancement for NA hydrolysis. Hydrolysis kinetics of phosphate esters catalyzed by ZnL are also investigated using bis(4‐nitrophenyl)phosphate (BNPP) and disodium 4‐nitrophenyl phosphate (NPP) as the substrates. The initial first‐order rate constant of catalytic hydrolysis for BNPP was 1.29×10^?7 s^?1 at pH 8.5, 35 °C and 0.1 mM catalyst concentration, about 1600‐fold acceleration over uncatalyzed hydrolysis. The pH dependence of the BNPP cleavage in aqueous buffer was shown as a sigmoidal curve with an inflection point around pH 8.25, which is nearly identical to the pK_a value of the catalyst from the potentiometric titration. The k_BNPP of BNPP hydrolysis promoted by ZnL is found to be 1.68×10^?3 M ^?1 s^?1, higher than that of NPP, and comparatively higher than those promoted by its other tridentate N,N′,N′′‐zinc analogues.     

Huggins constant k′ for flexible chain polymers

The Huggins constant k′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k′[η]²c² + …), is calculated. For polymers in the theta condition, k′ is estimated to be 0.5 < k_θ′ ≤ 0.7. For good solvent systems, the Peterson-Fixman theory of k′ has been modified; the equilibrium radial distribution function in the original theory is replaced with a parametric distribution for interpenetrating macromolecules in the shear force field. Comparison of the modified theory with experimental k′ for polystyrenes and poly(methyl methacrylates) of different molecular weights in various solvents shows good agreement. An empirical equation which correlates the Huggins constant k′ and the viscosity expansion factor α_η for polymers has been found to coincide well with the modified theory.     

Phosphodiester Cleavage Promoted by an Asymmetric Di­nuclear Zinc Complex: Synthesis,Structure, and Catalytic ­Activity

The dinuclear Zn^II complex [Zn₂L(DNBA)₂]BPh₄ · EtOH ( 1 ) (DNBA = 3,5‐dinitrobenzonic acid) with an asymmetric dinuclear ligand, N‐4‐methyl‐homopiperazine‐N′‐[N‐(2‐pyridylmethyl)‐N‐2‐(2‐pyridylethyl)amine]‐1,3‐diamino‐propan‐2‐ol (HL), was synthesized and characterized. Single crystal X‐ray crystallographic analysis shows that the coordination around the two Zn^II ions in 1 is significantly asymmetric, and the distance between both atoms is 3.426 Å, which is close to the Zn···Zn distance in related natural dinuclear metalloenzymes. Phosphodiesterase activity of Zn₂L in situ formed from a 2:1 mixture of Zn²⁺ ion and HL was investigated using bis(4‐nitrophenyl) phosphate (BNPP) as substrate. The pH dependence of the BNPP cleavage in aqueous buffer media reveals a bell‐shaped pH‐k_obs profile with an optimum at about pH 7.9, which is parallel to the formation of the dinuclear species Zn₂L‐OH obtained from the potentiometric titration. The catalytic rate constant (k_cat) is 6.30 × 10^–4 s^–1 at pH 7.9 and 25 °C, which is approx. 10⁸‐fold higher than that of the uncatalyzed reaction. The homopiperazine bound deprotonated Zn‐OH group is responsible for the hydrolysis reaction. The possible mechanism for the BNPP cleavage promoted by Zn₂L is proposed on the basis of kinetic and spectral analysis.