A clickable,highly soluble oligopeptide that easily forms organogels

An artificial peptide, N₃-GVGV-OMe (G, glycine; V, valine), which mimics the repeating GAGA (A, alanine) sequence in Bombix Mori silk, was synthesised via solution-phase synthesis. Compared with N₃-GAGA-OMe sequence, N₃-GVGV-OMe showed high solubility in common organic solvents (such as CHCl₃, THF and CH₂Cl₂), and easily formed organogels simply by adding poor solvents (such as toluene or ether) to the peptide solution at room temperature. The hierarchical nanostructure of N₃-GVGV-OMe organogel was dependent on the nature of the poor solvents, although in all cases, β-sheets were formed exclusively. Gels formed in ether showed higher level hierarchical assembly, as evidenced by AFM and CD studies. Solution-state FT-IR analysis showed that the pre-organisation of the peptides in solution was not significant, and well-defined antiparallel β-sheets were formed after the addition of the poor solvent. The high solubility and strong tendency for self-assembly of N₃-GVGV-OMe, together with its terminal azide group, might facilitate the modification of functional organic molecules even macromolecules for better nanostructure control.     

Kinetic Study of the Substitution Reactions of Triphenylphosphine with Chlorobenzyl Chlorides,Dimethylbenzyl Chloride,and Methylbenzyl Bromides in Various Two-Phase Organic Solvent/Water Media

The kinetics of the substitution reactions of triphenylphosphine (TP) with chlorobenzyl chlorides (CBC), 2,5-dimethylbenzyl chloride (DMBC), and methylbenzyl bromides (MBB) in aprotic organic solvent was studied under the extraction by water. The effects of water, agitation, organic solvent, reactant, and temperature were investigated. These reactions take place via the S_N2 mechanism and exhibit large and negative entropy of activation. The order of relative activity of solvents is CHCl₃ > CH₂Cl₂ ? C₆H₆. In CHCl₃, the order of relative reactivity of benzyl chloride (BC), benzyl bromide (BB), CBC, DMBC, and MBB toward reaction with TP is 2-MBB > 4-MBB > 3-MBB > BB > DMBC > BC > 2-CBC > 4-CBC > 3-CBC. These reactions produce quantitatively benzyltriphenylphosphonium salts, which are useful for synthesizing Z-form isomers of stilbenes via the two-phase Wittig reaction.     

Soluble poly (aryl ether)s containing naphthalene pendant group: synthesis, characterization and electrospinning

Two soluble poly(aryl ether)s were prepared conveniently from bis(4-hydroxy-3,5-dimethylphenyl)naphthylmethane (1) and two activated dihalide monomers including 4,4′-difluorobenzophenone and bis(4-chlorophenyl)sulfone by an aromatic nucleophilic substitution. The bulky naphthyl and tetramethyl pendant groups in the polymer backbone could decrease the packing density and intermolecular interaction of macromolecular chain and make these poly(aryl ether)s show a good solubility. They all could be dissolved in CHCl₃, CH₂Cl₂ and tetrahydrofuran at room temperature with a dissolvability of more than 10 wt%. Furthermore, the poly(aryl ether)s could be electrospun into microfiber (10–15 μm) with nanopores (200–350 nm). The morphologies of these fibers were characterized by scanning electron microscopy. The porous morphology on the fiber surface was also investigated using scanning probe microscope.     

The Ozonolysis of Longifolene: A Tool for the Preparation of Useful Chiral Compounds. Configuration Determination of New Stereogenic Centers by NMR Spectroscopy and X‐Ray Crystallography

The ozonolysis of (+)‐longifolene ( 1 ) in different solvents (Et₂O, CH₂Cl₂, CHCl₃, acetone) at ?80° provided quantitatively longifolene epoxide ( 3 ) as a single diastereoisomer in which the O‐atom is endo‐positioned (Scheme 2). Upon warming to room temperature, the epoxide remained stable only in acetone and was isolated as a low‐melting crystalline compound. In CH₂Cl₂, Et₂O, or CHCl₃ solution, epoxide 3 rapidly rearranged to the isomeric enols 4 and 5 , which underwent further rearrangement to give the exo‐aldehyde 6 . On standing for several weeks in CH₂Cl₂ solution, or in CHCl₃ and Et₂O as well, at room temperature, aldehyde 6 slowly rearranged into its epimer 7 . The aldehydes 6 and 7 were isolated on the preparative scale for further synthetic use. The addition of methylmagnesium iodide to 6 and 7 provided the corresponding alcohols 13 / 14 and 15 / 16 , respectively, which were isolated as pure diastereoisomers (Scheme 4). The configurations of the new chiral centers in 13 – 16 were determined by NMR methods and X‐ray crystallography.     

The effect of polymer side chains on vapor sorption in polyacrylate and polymethacrylate solutions

The segment fraction Ψ₁ activity coefficients, a₁/Ψ₁, of solvents have been determined by the piezoelectric sorption method for 0.1 ≤ Ψ₁ ≤ 0.5 in binary solutions of chlorinated methanes [carbon tetrachloride (CCl₄), chloroform (CHCl₃), and dichloromethane (CH₂Cl₂)] with aromatic hydrocarbons (benzene and toluene) in poly(methyl methacrylate), poly(methyl acrylate), poly(ethyl methacrylate), and poly(n-butyl acrylate) at 23.5°C. The present results for toluene in PMMA agree with previously published values obtained by gas-liquid chromatography. For CCl₄ and the aromatic hydrocarbons, the polymer–solvent interaction parameter χ is positive and constant, while for the polar solvents (CHCl₃ and CH₂Cl₂), χ is negative and increases with increasing Ψ₁. The effect of the polymer side chains on vapor sorption in nonpolar and polar solvent systems is discussed in terms of the χ parameter.     

Lyotropic mesomorphic formation of cellulose in trifluoroacetic acid-chlorinated-alkane solvent mixtures at room temperature

Mixtures of trifluoroacetic acid (TFA)-1,2-dichloroethane (1,2-DCE); TFA-dichloromethane (CH₂Cl₂); and TFA-trichloromethane (CHCl₃) are excellent cellulose solvents at room temperature. TFA-1,2-DCE and TFA-CH₂Cl₂ are superior to pure TFA. Lyotropic cellulose mesophases were obtained in (20% w/v) solutions of cellulose in these solvent mixtures. The optical and optical rotatory powers of the solutions suggest that the lyotropic mesophase of cellulose is cholesteric. This implies that cellulose molecules are arranged in helical form in these solvent systems.     

Synthesis of 1,2,4,5,7,8-hexaoxonanes by iodine-catalyzed reactions of bis(1-hydroperoxycycloalkyl) peroxides with ketals

Iodine-catalyzed reactions of bis(1-hydroperoxycycloalkyl) peroxides with ketals give, via replacement of two alkoxy groups, the cyclic peroxides, 1,2,4,5,7,8-hexaoxonanes, in up to 82% yields. The cyclization is very sensitive to the solvent nature. Among MeCN, Et₂O, THF, CHCl₃, CH₂Cl₂, hexane, and MeOH, the best results were achieved with the first three solvents.     

Synthesis and properties of new orange red light‐emitting hyperbranched and linear polymers derived from 3,5‐dicyano‐2,4,6‐tristyrylpyridine

Two new orange red light‐emitting hyperbranched and linear polymers, poly(pyridine phenylene)s P1 and P2, were prepared by the Heck coupling reaction. In particular, an A₂ + B₃ approach was developed to synthesize conjugated hyperbranched polymer P2 via one‐pot polycondensation. The polymers were characterized by NMR, Fourier transform infrared, ultraviolet–visible, and elemental analysis. They showed excellent solubility in common solvents such as tetrahydrofuran, CH₂Cl₂, CHCl₃, and N,N‐dimethylformamide and had high molecular weights (up to 6.1 × 10⁵ and 5.8 × 10⁵). Cyclic voltammetry studies revealed that P2 had a low‐lying lowest unoccupied molecular orbital energy level of ?3.22 eV and a highest occupied molecular orbital energy level of ?5.43 eV. The thin film of P2 emitted strong orange‐red photoluminescence at 595 nm. A double‐layer light‐emitting diode fabricated with the configuration of indium tin oxide/P2/tris(8‐hydroxy‐quinoline)aluminum/Al emitted orange‐red light at 599 nm, with a brightness of 662 cd/m² at 7 V and a turn‐on voltage of 4.0 V; its external quantum efficiency was calculated to be 0.19% at 130.61 mA/cm². This indicated that this new electroluminescent polymer (P2) based on 3,5‐dicyano‐2,4,6‐tristyrylpyridine could possibly be used as an orange‐red emitter in polymer light‐emitting displays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 493–504, 2005     

Radio-high performance liquid chromatographic study on radioactive38Cl compounds

Reaction of recoild³⁸Cl atoms with o-dichlorobenzene in the presence of carbon tetrachloride or iodine has been studied by using radio-high performance liquid chromatography. The major products were detected by a 4-channel-wavelengths spectrophotometric detector. The radioactivity of³⁸Cl compounds including minor products was measured with a NaI(T1) scintillation detector. The main products found were³⁸Cl labeled HCl/Cl₂, CHCl₃, CCl₄, o-, p-, m-C₆H₆Cl₂ and polymer, whereas only minor products such as HCl/Cl₂, CHCl₃, C₂Cl₆, C₆H₃Cl₃, and polymer were found in the radio-chromatogram. The reaction mechanisms of recoil³⁸Cl atom are briefly described.     

Synthesis of Poly(silyne-co-hydridocarbyne) for Silicon Carbide Production

Pre-ceramic polymers have previously been shown to be polymeric precursors to silicon carbide, diamond and diamond-like carbon. Here, we report the synthesis of a pre-ceramic polymer, poly(silyne-co-hydridocarbyne), which was electrochemically synthesized from one monomer containing both silicon and carbon in its structure. The polymer is soluble in common solvents such as CHCl₃, CH₂Cl₂ and THF. Since the polymer contains both silyne and carbyne on its backbone, it can be easily converted to silicon carbide upon heating under an ambient inert atmosphere, or to SiO₂ under ambient air atmosphere. Poly(silyne-co-hydridocarbyne) was characterized with UV/Vis spectroscopy, FTIR, ¹H-NMR, GPC and Raman spectroscopy. Conversion of the polymer to SiC ceramic was accomplished by heating at 1000 and 750°C under an argon atmosphere and characterized with optical microscopy, SEM, X-Ray and Raman spectroscopies.     

A practical and highly efficient transfer hydrogenation of aryl azides using a [Ru(p-cymene)Cl2]2 catalyst and sodium borohydride

Various aniline derivatives were synthesized by selective reduction of aryl azides in the presence of a dichloro(p-cymene)ruthenium(II) dimer ([Ru(p-cymene)Cl₂]₂) via hydrolysis of sodium borohydride. The hydrogenation reactions were carried out in aqueous media at room temperature. Most of the reactions were completed within 10 min with quantitative yields.     

Kinetics and mechanisms of diels-alder addition of tetracyanoethylene to anthracene derivatives—II : Solvent effects

The effect of change of solvent on the rate of Diels-Alder addition of tetracyanoethylene (TCNE) to anthracene has been investigated using solvents CCl₄, CHCl₃ and CH₂Cl₂. Solvent effects were measured on the intermediate complex and on the starting materials from solubility measurements. From this, solvent effects on the transition state alone can be evaluated. These effects were remarkable similar to those measured for both the initial state and the intermediate complex suggesting an “early” transition state having a structure similar to that of the intermediate. From the correlation of ΔG_t^≠ (the free energy of transfer from CCl₄ to another solvent for the transition state alone) with the solubility parameter δ², the molar volume of the transition state can be estimated. The result again suggests that the transition state is more “factor” than product-like.     

Kinetic Study of Mercury(II) Transport through a Bulk Liquid Membrane Using Cyanex 301 as Carrier

A kinetic study of Hg(II) ions transport through a bulk liquid membrane (BLM) was investigated. The commercially available liquid bis(2,4,4‐trimethyl(pentyl) dithiophosphinic acid) (Cyanex 301) was employed as mobile carrier. The influences of the carrier concentration in the liquid membrane, HNO₃ concentration in the feed phase, type of organic solvent, composition of the receiving phase, and stirring speed on mass transfer were studied. Various solvents including CH₂Cl₂, CHCl₃, C₂H₄Cl₂ and CCl₄ were used as organic membrane. Among the solvents, CHCl₃ provided the superior results. The kinetic parameters (k₁, k₂, R_m^max, t^max, J_d^max, and J_a^max) were calculated for the interface reaction assuming two consecutive, irreversible first‐order reactions. The analysis of Hg(II) accumulation in liquid membrane and the rate‐controlling step under different experimental conditions were elucidated. The experiments demonstrated that Cyanex 301 is an appropriate carrier for Hg(II) transport through liquid membrane.     

Anion-induced switching of the helical orientation of a chiral indolocarbazole dimer

An indolocarbazole dimer, containing chiral urea appendages, that adopts a helically folded conformation by intramolecular hydrogen bonds as proven by ¹H NMR and circular dichroism (CD) spectroscopy has been prepared. Owing to the preferential formation of one helical conformer, strong CD signals appear in relatively non-polar solvents such as chloroform (CHCl₃) and dichloromethane (CH₂Cl₂) but the signal is negligible in dimethyl sulfoxide (DMSO). In addition, the optical rotation of the dimer is highly sensitive to the polarity of solvents. For example, the magnitude of the specific rotation ([α]_D) is ? 934° in CH₂Cl₂ and ? 657° in CHCl₃ but it is only ? 75° in DMSO. These observations suggest that the dimer folds to a helical structure by intramolecular hydrogen bonds in relatively non-polar solvents but exists in an unfolded extended conformation in polar solvents such as DMSO. The dimer strongly binds anions such as chloride, acetate and sulfate by multiple hydrogen bonds. In addition, anion binding leads to considerable CD spectral changes with the different pattern and degree of Cotton effects depending on the kind of anions. The dimer may be therefore utilised for the construction of an anion-responsive chiroptical sensor or switch.     

Reactions with samarium diiodide in polymer synthesis

Reactions induced by Sml₂, such as reduction, coupling and cyclization are occurring in high yield upon mild conditions. It is due to the high redox potential of divalent samarium. Now reactions with Sml₂ are used in the polymer synthesis as well. By the coupling reaction of various diacid chlorides poly-α-diketones having molecular weight up to 20000 have been obtained at room temperature in quantitative yield. Isomeric difluorobenzils prepared by the one-step reaction of Sml₂ and relevant fluorobenzoyl chlorides have been used in the nucleophylic substitution reaction with bisphenols. Film-forming high molecular weight copolyetherketone-α-diketones have been synthesized when such difluorobenzils have been used as the comonomers in the polycondensation of 4,4'-difluorobenzophenone and bisphenols. All these polymers bearing α-diketogroups have been transformed into linear and network polyquinoxalines by their reaction with aromatic (bis)o-diamines. Aromatic polypinacols have been synthesized by the reaction of dialdehydes and Sml₂ in THF under mild conditions. The availability of the reactive α-hydroxy groups made it possible to carry out polymer chain reactions. It was stated that the imide cycle is reduced by Sml₂ at room temperature. The treatment of polyimides by Sml₂ leads to the change of polymer properties, mainly heat resistance and solubility. The possibility of formation of Si-Si bonds by reductive coupling of organochlorosilanes with the use of Sml₂ instead of Na has been shown. It was found that the reaction of diorganodichlorosilanes with Sml₂ easily proceeds in THF solution at room temperature to yield α,ω-dichloro-oligosilanes.     

Alkoxytelluration of Allylbenzene

(2-Alkoxy-3-phenylpropyl)trichlorotellanes were synthesized by regioselective reaction of tellurium tetrachloride with allylbenzene in the system MeOH–CH₂Cl₂, as well as by nucleophilic substitution of chlorine in trichloro(2-chloro-3-phenylpropyl)tellane in MeOH–CH₂Cl₂ and EtOH–CHCl₃. Allylbenzene reacted with tellurium tetrabromide on heating in methanol or ethanol. The reduction of (2-alkoxy-3-phenylpropyl) trihalotellanes with NaBH₄ in H₂O–THF gave 1,2-bis(2-alkoxy-3-phenylpropyl)ditellanes.     

Synthesis of iron-containing polymers with azo dyes in the backbones or side chains

The synthesis of cationic cyclopentadienyliron-containing polymers with pendent azobenzene chromophores was accomplished via metal-mediated nucleophilic aromatic substitution reactions. All of the desired polymers were isolated as vibrantly coloured materials and displayed excellent solubility in polar aprotic solvents. Cationic and neutral cyclopentadienyliron polymers incorporating azo dyes in the backbone were also prepared. Reactions of azo dyes with dichlorobenzene complexes allowed for the isolation of cationic cyclopentdienyliron (CpFe₊) complexes with azo dye chromophores. These complexes were then reacted with 1,1′-ferrocenedicarbonyl chloride to produce the trimetallic monomers with terminal chloro groups. These monomers contained two pendent CpFe₊ cations and a neutral iron moiety in the backbone. Nucleophilic substitution reactions of these monomers with oxygen and sulfur containing dinucleophiles gave rise to a new class of polymeric materials. The pendent CpFe₊ moieties could also be cleaved from the polymer backbones using photolysis to afford novel ferrocene based polymers. The UV-vis spectra of the organoiron monomers and polymers display similar wavelength maxima however incorporating azobenzene chromophores with electron-withdrawing substituent into the polymer chains resulted in bathochromic shifts of the λ_max values.     

Fluorescent Recognition of Small Organic Molecules Based on Supramolecular Aggregation/Deaggregation of Planar Cu(II) Coordination Complex

A Cu(II) coordination complex ( 1 ) with Schiff ligand derived from diaminomaleonitrile was synthesized and characterized, in which the ligand is rigid, planar and conjugated. The complex 1 displays an interesting fluorescent property relative to solvents which can be turned‐on by CH₂Cl₂ and CHCl₃ solvent molecules. The mechanism of this selective fluorescence emission has been studied based on the crystal structure and the spectrum analysis. The tuning on and off fluorescence of complex 1 can be controlled by the process of supramolecular aggregation/deaggregation in different solvents.     

Cationic ring‐opening polymerization of novel 1,3‐dehydroadamantanes with various alkyl substituents: Synthesis of thermally stable poly(1,3‐adamantane)s

Cationic ring‐opening polymerizations of 5‐alkyl‐ or 5,7‐dialkyl‐1,3‐dehydroadamantanes, such as 5‐hexyl‐ ( 4 ), 5‐octyl‐ ( 5 ), 5‐butyl‐7‐isobutyl‐ ( 6 ), 5‐ethyl‐7‐hexyl‐ ( 7 ), and 5‐butyl‐7‐hexyl‐1,3‐dehydroadamantane ( 8 ), were carried out with super Brønsted acids, such as trifluoromethanesulfonic acid or trifluoromethanesulfonimide in CH₂Cl₂ or n‐heptane. The ring‐opening polymerizations of inverted carbon–carbon bonds in 4–8 proceeded to afford corresponding poly(1,3‐adamantane)s in good to quantitative yields. Poly( 4–8 )s possessing alkyl substituents were soluble in 1,2‐dichlorobenzene, although a nonsubstituted poly(1,3‐adamantane) was not soluble in any organic solvent. In particular, poly( 8 ) exhibited the highest molecular weight at around 7500 g mol^?1 and showed excellent solubility in common organic solvents, such as THF, CHCl₃, benzene, and hexane. The resulting poly( 4–8 )s containing adamantane‐1,3‐diyl linkages showed good thermal stability, and 10% weight loss temperatures (T₁₀) were observed over 400 °C. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4111–4124     

Stereospecific polymerization of α-methylstyrene by friedel-crafts catalysts

The relationship between stereoregularity and polymerization conditions of α-methylstyrene has been studied by means of NMR spectra. The effects of solvents and various Freidel-Crafts catalysts have been investigated. The stereoregularity of poly-α-methylstyrene increased with increased polymer solubility in the solvent used and with decreasing polymerization temperature. This behavior is completely different from the stereospecific polymerization of vinyl ethers and methyl methacrylate in homogeneous systems. This may be due to the strong steric repulsion exerted by the two substituents in the α-position of α-methylstyrene. For example, with BF₃ · O(C₂H₅)₂ as catalyst at ?78°C., atactic polymer is obtained in n-hexane, a nonsolvent for α-methylstyrene, whereas highly stereoregular polymer is produced in toluene or methylene chloride, good solvents for the polymer. However, the polarity of the solvent and the nature of the catalyst hardly affect the stereoregularity of the polymer.