220-MHz NMR spectra of acrylic monomer–2-substituted 1,3-diolefin alternating copolymers

An investigation by 220-MHz NMR spectroscopy was carried out on the alternating copolymers of acrylic monomer with 2-substituted 1,3-diolefin. The chain structures were determined. The acrylic monomers used were methyl methacrylate (MMA), acrylonitrile (AN), and methacrylonitrile (MAN); isoprene (IP) and chloroprene (CLP) were the 1,3-diolefins. In the MAN–IP alternating copolymer, the 1-position methylene protons of IP showed an AB quartet peak, confirming the α-1 linkage structure. Similarly, in the MMA–CLP and AN–CLP copolymers, the 1-position methylene protons of CLP showed and AB quartet and an ABX pattern, respectively, confirming the α-1 linkage structure in both these cases also. The α-1 linkage structure was also revealed by the decoupling technique in the MAN–CLP alternating copolymer. The AN–IP and MMA–IP alternating copolymers also possess a bond between the α-position of the acrylic monomer and the 1-position of IP. The monomeric units in the alternating copolymers of acrylic monomers with 2-substituted 1,3-diolefins were generally linked at the α-position of acrylic monomer and the 1-position of 1,3-diolefin. On the other hand, in the Diels-Alder adducts of acrylic monomer with 2-substituted 1,3-diolefin, the reaction takes place between the α-position of acrylic monomer and the 4-position of 1,3-diolefin. The regioselectivity of the alternating copolymers and the Diels-Alder adducts is quite compatible with the expectations from molecular orbital theory.     

Influence of amino acid side chain packing on Fe-methionine coordination in thermostable cytochrome C

Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability.     

Installation of carbon chain onto 2-cyclohexene-1,4-diol monoacetate

Alkylation of cyclohexenyl monoacetate 1 with R₂Cu(CN)(MgCl)₂ or RMgBr/CuCN (cat.) in Et₂O produced trans 1,2-isomers 4, while arylation and alkenylation of 1 was accomplished with lithium borates 5 and a nickel cat. to afford trans 1,4-isomers 3 selectively. Furthermore, several transformations of the products were carried out to demonstrate synthetic advantages of the present reactions.     

Nature of the active component in the catalytic system prepared from titanium(III) chloride(AA), ethylaluminum dichloride,and tetrakis(dimethylamino)silane,in the polymerization of propylene

The chemistry of the titanium(III) chloride(AA)–ethylaluminum dichloride–tetrakis-(dimethylamino)silane system for the polymerization of propylene was studied. A complex of ethylaluminum dichloride with tetrakis(dimethylamino)silane was isolated. It was shown that this complex contains ethylaluminum dichloride and tetrakis(dimethylamino)silane in the ratio of 2:1. This complex with titanium(III) chloride is responsible for the polymerization activity.     

Ultra-slow Relaxation Dynamics in Triglycine Sulfate and D-Sorbitol Studied by Time-resolved Spectroscopy

The ultra-slow modes with a relaxation time much longer than 1 ns are discovered by a time-resolved spectroscopy in uniaxial ferroelectric (NH₂CH₂COOH)₃H₂SO₄ (TGS) and in glass-former HOCH₂(CHOH)₄CH₂OH (D-sorbitol). A mode discovered in TGS is a thermal relaxational mode and is proved to be the physical origin of the central peak found by Brillouin scattering. Two modes are discovered in D-sorbitol. One is a thermal relaxational mode. The other is a mode characterized by the Kohlraush-Williams-Watts function with a relaxation time _R. A remarkable result is that _R indicates a critical behavior not at the liquid-glass transition temperature T_g =–7°C but at the ergodic to nonergodic transition temperature T_c=33°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

Polymerization of vinyl monomers by the reaction products of diphenyl sulphoxide with potassium

Diphenyl sulphoxide (DPSO) reacts with an equimolar amount of potassium (K) in tetrahydrofuran (THF) at ?78° to form a reddish-black solution, giving an electron spin resonance (ESR) signal only below ?70°. The signal is attributed to a very labile DPSO anion radical. The solution of DPSO-K (1/1) reaction products reacts further with another molecular amount of K at this temperature to give no ESR signal. The DPSO-K (1/1) reaction products initiates the polymerization of acrylonitrile (AN), but not the polymerizations of methyl methacrylate (MMA), styrene (St) or isoprene (IP). The active species of the solution initiating the polymerization of AN is assumed to be potassium benzene sulphenate from analyses of the solution and the infra-red spectrum of AN oligomers obtained using the complex. The DPSO-K (1/2) reaction products solution initiates the polymerization of MMA, St and IP as well as AN. The active species initiating the polymerization of MMA, St or IP is assumed to be phenylpotassium.     

Polymerization of vinyl monomers by diphenylsulfone–potassium complexes

Diphenylsulfone (DPSO₂) was found to react with an equimolar amount of potassium in tetrahydrofuran (THF), dimethoxyethane (DME), or diglyme (DG) at reflux or an elevated temperature to yield a reddish-black solution, giving an electron spin resonance (ESR) signal. The signal was attributed to the formation of relatively labile DPSO₂ anion radical. The apparent effects of solvents on the reactivity of DPSO₂ with potassium depended on the polarities and the solvation powers: benzene ? toluene ? dioxane ? tetrahydrofuran < monoglyme < diglyme. The monopotassium complex was found to react further with another molecular amount of the metal to yield a dark blue solution giving no ESR signal. The monopotassium complex initiated the polymerization of acrylonitrile (AN). It did not, however, initiate the polymerization of methyl methacrylate (MMA), styrene (St), or isoprene (IP). The active species of the monopotassium complex that initiated the polymerization of AN was found from analyses of the reaction products and the infrared spectrum of oily oligomer of AN obtained by the complex to be potassium benzenesulfinate. The dipotassium complex was found to initiate the polymerization of MMA, St, IP and AN. The active species of the dipotassium complex that initiated the polymerization of MMA, St, or IP was found from analyses of the reaction products and the infrared spectrum of the oily oligomer of MMA obtained by the complex to be phenyl potassium.     

A new approach to the synthesis of pyridazino[4,5-c]pyridazinones

The reaction of 5-hydrazinopyridazin-3(2H)-ones 1 with α-keto diester 2 in acetic acid afforded the corresponding 4,6-dihydropyridazino[4,5-c]pyridazin-5(1H)-ones 3 and pyrrolo[2,3-d)pyridazin-4(5H)-ones 4 . Compounds 3 were also obtained from 4-bromo-5-hydrazinopyridazin-3(2H)-ones 8 and 2 under milder conditions. 5-Bromo-4-hydrazinopyridazin-3(2H)-one 9 , the regioisomer of 8b , also reacted readily with 2a to give 4,7-dihydropyridazino[4,5-c]pyridazin-8(1H)-one 10b , the regioisomer of 3b .     

Ionic liquid crystal as a hole transport layer of dye-sensitized solar cells

Use of a new ionic liquid crystal, 1-dodecyl-3-methylimidazolium iodide, and iodine as an electrolyte of dye-sensitized solar cells leads to a high short circuit photocurrent density and a high light-to-electricity conversion efficiency, due to a self-assembled structure of the imidazolium cations, resulting in high conductivity of the electrolyte.