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2014 Volume 25 Issue 11
2014, 25(11): 1407-1410
doi: 10.1016/j.cclet.2014.08.002
Abstract:
Novel porous aromatic frameworks (PAF-53 and PAF-54) have been obtained by the polymerization of amino compound (p-phenylenediamine and melamine) and cyanuric chloride. They display a certain amount of CO2 adsorption capacity and highly selective separation of CO2/CH4 and CO2/N2 as 18.1 and 83 by Henry Law respectively. They may be applied as ideal adsorbents to separate and capture CO2.
Novel porous aromatic frameworks (PAF-53 and PAF-54) have been obtained by the polymerization of amino compound (p-phenylenediamine and melamine) and cyanuric chloride. They display a certain amount of CO2 adsorption capacity and highly selective separation of CO2/CH4 and CO2/N2 as 18.1 and 83 by Henry Law respectively. They may be applied as ideal adsorbents to separate and capture CO2.
2014, 25(11): 1411-1415
doi: 10.1016/j.cclet.2014.06.016
Abstract:
A series of SBA-15 supported bimetallic Rh-Ni catalysts with different weight ratio of Rh/Ni in the range of 0-0.04 were prepared for carbon dioxide reforming of methane. The doping effect of Rh on catalytic activity as well as carbon accumulation and removal over the catalysts was studied. The characterization results indicated that the addition of a small amount of Rh promoted the reducibility of Ni particles and decreased the Ni particle size. During the dry reforming reaction, the carbon deposition was originated from CH4 decomposition and CO disproportionation. The Rh-Ni catalyst with smallmetallic particle size inhibited the carbon formation and exhibited high efficiency in the removal of coke. In comparison with bare Ni-based catalyst, the Rh-Ni bimetallic catalysts showed high activity and stability in the dry reforming of methane.
A series of SBA-15 supported bimetallic Rh-Ni catalysts with different weight ratio of Rh/Ni in the range of 0-0.04 were prepared for carbon dioxide reforming of methane. The doping effect of Rh on catalytic activity as well as carbon accumulation and removal over the catalysts was studied. The characterization results indicated that the addition of a small amount of Rh promoted the reducibility of Ni particles and decreased the Ni particle size. During the dry reforming reaction, the carbon deposition was originated from CH4 decomposition and CO disproportionation. The Rh-Ni catalyst with smallmetallic particle size inhibited the carbon formation and exhibited high efficiency in the removal of coke. In comparison with bare Ni-based catalyst, the Rh-Ni bimetallic catalysts showed high activity and stability in the dry reforming of methane.
2014, 25(11): 1416-1418
doi: 10.1016/j.cclet.2014.05.052
Abstract:
A novel 2,6-dimethyl-β-CD bonded and silica based HPLC chiral stationary phase (CSP) was prepared. The diphenylmethane diisocyanate (MDI) was applied for the first time in the immobilization of 2, 6-dimethyl-β-CD onto the surface of aminized silica gel undermild conditions. The compositematerials obtained were used as the CSP for chiral separation processes and this kind of CSP exhibits good enantioselectivity for a variety of chiral compounds under reversed-phase conditions.
A novel 2,6-dimethyl-β-CD bonded and silica based HPLC chiral stationary phase (CSP) was prepared. The diphenylmethane diisocyanate (MDI) was applied for the first time in the immobilization of 2, 6-dimethyl-β-CD onto the surface of aminized silica gel undermild conditions. The compositematerials obtained were used as the CSP for chiral separation processes and this kind of CSP exhibits good enantioselectivity for a variety of chiral compounds under reversed-phase conditions.
2014, 25(11): 1419-1422
doi: 10.1016/j.cclet.2014.08.003
Abstract:
A series of novel ester-capped carbosilane dendrimers (G0-COOCH3-G2-COOCH3) were designed and successfully synthesized via a hybrid divergent-convergent method through a facile hydrosilylation reaction. The structures of these dendrimers were confirmed by FTIR, 1H NMR, and HRMS analyses.
A series of novel ester-capped carbosilane dendrimers (G0-COOCH3-G2-COOCH3) were designed and successfully synthesized via a hybrid divergent-convergent method through a facile hydrosilylation reaction. The structures of these dendrimers were confirmed by FTIR, 1H NMR, and HRMS analyses.
2014, 25(11): 1423-1427
doi: 10.1016/j.cclet.2014.06.004
Abstract:
A ZnCl2-modified ion exchange resin as the catalyst for bisphenol-A synthesis was prepared by the ion exchange method. Scanning electron microscope (SEM), Fourier transform infrared spectrophotometer (FT-IR), thermo gravimetric analyzer (TGA) and pyridine adsorbed IR were employed to characterize the catalyst. As a result, the modified catalyst showed high acidity and good thermal stability. Zn2+ coordinated with a sulfonic acid group to form a stable active site, which effectively decreased the deactivation caused by the degradation of sulfonic acid. Thus the prepared catalyst exhibited excellent catalytic activity, selectivity and stability compared to the unmodified counterpart.
A ZnCl2-modified ion exchange resin as the catalyst for bisphenol-A synthesis was prepared by the ion exchange method. Scanning electron microscope (SEM), Fourier transform infrared spectrophotometer (FT-IR), thermo gravimetric analyzer (TGA) and pyridine adsorbed IR were employed to characterize the catalyst. As a result, the modified catalyst showed high acidity and good thermal stability. Zn2+ coordinated with a sulfonic acid group to form a stable active site, which effectively decreased the deactivation caused by the degradation of sulfonic acid. Thus the prepared catalyst exhibited excellent catalytic activity, selectivity and stability compared to the unmodified counterpart.
2014, 25(11): 1428-1434
doi: 10.1016/j.cclet.2014.06.005
Abstract:
Poly(ethylene oxide), poly(vinyl pyrrolidone) (PEO/PVP), lithium perchlorate salt (LiClO4) and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate (EC) based complex exhibits a maximum ionic conductivity value of the order of 2.7279×10-4 S cm-1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO (72%)/PVP (8%)/LiClO4 (8%)/EC (12%) has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400-450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.
Poly(ethylene oxide), poly(vinyl pyrrolidone) (PEO/PVP), lithium perchlorate salt (LiClO4) and different plasticizer based, gel polymer electrolytes were prepared by the solvent casting technique. XRD results show that the crystallinity decreases with the addition of different plasticizers. Consequently, there is an enhancement in the amorphousity of the samples responsible for the process of ion transport. FTIR spectroscopy is used to characterize the structure of the polymer and confirms the complexation of plasticizer with host polymer matrix. The ionic conductivity has been calculated using the bulk impedance obtained through impedance spectroscopy. Among the various plasticizers, the ethylene carbonate (EC) based complex exhibits a maximum ionic conductivity value of the order of 2.7279×10-4 S cm-1. Thermal stability of the prepared electrolyte films shows that they can be used in batteries at elevated temperatures. PEO (72%)/PVP (8%)/LiClO4 (8%)/EC (12%) has the maximum ionic conductivity value which is supported by the lowest optical band gap and lowest intensity in photoluminescence spectroscopy near 400-450 nm. Two and three dimensional topographic images of the sample having a maximum ionic conductivity show the presence of micropores.
2014, 25(11): 1435-1440
doi: 10.1016/j.cclet.2014.06.027
Abstract:
The objective of this study was to investigate the potential of methoxy polyethylene glycol (mPEG) grafted chitosan (mPEG-g-CS) to be used as a drug carrier. mPEG-g-CS was successfully synthesized by one-step method with formaldehyde. The substitution degree of mPEG on chitosan was calculated by elemental analysis and was found to be (3.23±0.25)%. mPEG-g-CS self-assembled micelles were prepared by ultrasonic method with the controlled size of 178.5-195.1 nm and spherical morphology. Stable dispersion of the micelles was formed with the zeta potential of 2.3-30.2 mV. 5-Fluorouracil (5-FU), an anticancer chemotherapy drug, was used as a model drug to evaluate the efficiency of the new drug delivery carrier. The loading efficiency of 5-FU was (4.01±0.03)%, and the drug-loaded mPEG-g-CS self-assembled micelle showed a controlled-release effect. In summary, the mPEG-g-CS self-assembled micelle is proved to be a promising carrier with controlled particle size and controlled-release effect. Therefore, it has great potential for the application as 5-FU carriers for effective anti-tumor activity.
The objective of this study was to investigate the potential of methoxy polyethylene glycol (mPEG) grafted chitosan (mPEG-g-CS) to be used as a drug carrier. mPEG-g-CS was successfully synthesized by one-step method with formaldehyde. The substitution degree of mPEG on chitosan was calculated by elemental analysis and was found to be (3.23±0.25)%. mPEG-g-CS self-assembled micelles were prepared by ultrasonic method with the controlled size of 178.5-195.1 nm and spherical morphology. Stable dispersion of the micelles was formed with the zeta potential of 2.3-30.2 mV. 5-Fluorouracil (5-FU), an anticancer chemotherapy drug, was used as a model drug to evaluate the efficiency of the new drug delivery carrier. The loading efficiency of 5-FU was (4.01±0.03)%, and the drug-loaded mPEG-g-CS self-assembled micelle showed a controlled-release effect. In summary, the mPEG-g-CS self-assembled micelle is proved to be a promising carrier with controlled particle size and controlled-release effect. Therefore, it has great potential for the application as 5-FU carriers for effective anti-tumor activity.
2014, 25(11): 1441-1444
doi: 10.1016/j.cclet.2014.05.047
Abstract:
Isoquinoline reacts with dialkyl acetylenedicarboxylates in the presence of kojic acid or 8-hydroxyquinoline to generate 1,2-dihydroisoquinoline derivatives. The simplicity, mild reaction conditions and high yields of products make it an interesting process compared to other approaches. The compounds have been analyzed for antibacterial activity against Gram negative and Gram positive bacteria. The results indicated that 1,2-dihydroisoquinolines derived from kojic acid are effective against all of the studied bacteria especially against Bacillus subtilis, while the products obtained from 8-hydroxyquinoline are active only against Gram positive bacteria.
Isoquinoline reacts with dialkyl acetylenedicarboxylates in the presence of kojic acid or 8-hydroxyquinoline to generate 1,2-dihydroisoquinoline derivatives. The simplicity, mild reaction conditions and high yields of products make it an interesting process compared to other approaches. The compounds have been analyzed for antibacterial activity against Gram negative and Gram positive bacteria. The results indicated that 1,2-dihydroisoquinolines derived from kojic acid are effective against all of the studied bacteria especially against Bacillus subtilis, while the products obtained from 8-hydroxyquinoline are active only against Gram positive bacteria.
2014, 25(11): 1445-1448
doi: 10.1016/j.cclet.2014.05.031
Abstract:
Thioxanthone-based N-phthalimidoamino acid ammonium salt (thioxanthen-DBU) as a photocaged base was synthesized and characterized. The photochemical properties and initiation mechanism were analyzed. It was found that the compound absorbs over the UV and visible region with relatively high absorption coefficients. Furthermore, the covalent binding of N-phthalimidoamino acid and type Ⅱ chromophores (thioxanthone, TX) remarkably improved the photoreactivity. Specifically, in combination with a benzoyl peroxide initiator, thioxanthen-DBU was able to initiate the amine-mediated redox photopolymerization of trimethylol propane triacrylate (TMPTA), and an excellent photopolymerization profile was obtained.
Thioxanthone-based N-phthalimidoamino acid ammonium salt (thioxanthen-DBU) as a photocaged base was synthesized and characterized. The photochemical properties and initiation mechanism were analyzed. It was found that the compound absorbs over the UV and visible region with relatively high absorption coefficients. Furthermore, the covalent binding of N-phthalimidoamino acid and type Ⅱ chromophores (thioxanthone, TX) remarkably improved the photoreactivity. Specifically, in combination with a benzoyl peroxide initiator, thioxanthen-DBU was able to initiate the amine-mediated redox photopolymerization of trimethylol propane triacrylate (TMPTA), and an excellent photopolymerization profile was obtained.
2014, 25(11): 1449-1454
doi: 10.1016/j.cclet.2014.05.049
Abstract:
In this work, solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extractionmaterial and its composite was coated on a stainless steel wire through sol- gel technique for the solid phase microextraction. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02-15.0 μg/L for water samples, and 0.2-60.0 μg/kg for soil samples, with the correlation coefficients (r) of 0.9966-0.9987. The limits of detection of the method were 0.0025-0.005 μg/L for water samples, and 0.02-0.04 μg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%-113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.
In this work, solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extractionmaterial and its composite was coated on a stainless steel wire through sol- gel technique for the solid phase microextraction. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02-15.0 μg/L for water samples, and 0.2-60.0 μg/kg for soil samples, with the correlation coefficients (r) of 0.9966-0.9987. The limits of detection of the method were 0.0025-0.005 μg/L for water samples, and 0.02-0.04 μg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%-113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.
2014, 25(11): 1455-1460
doi: 10.1016/j.cclet.2014.06.014
Abstract:
In this study, Fe3O4 nanoparticles (Fe3O4 NPs) were successfully prepared via oxidation-precipitation method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The characterization results indicated that Fe3O4 NPs with regular crystal structure and a narrow of diameters had been synthesized successfully and had high purity. A series of experiments were carried out to investigate the degradation of Orange Ⅱ by the obtained heterogeneous Fe3O4 catalysts in the presence of H2O2. The response surface methodology (RSM) based on Box-Behnken design (BBD) was employed to design and optimize individual and interactive effects of the four main independent parameters (catalyst loading, initial pH, reaction temperature and H2O2 concentration) on decolorization efficiency of Orange Ⅱ. A significant quadratic model (p-value <0.0001, R2=0.9369) was derived using analysis of variance (ANOVA). Optimum conditions were catalyst loading of 1.5 g/L, initial pH of 2.7, reaction temperature of 42℃ and H2O2 concentration of 22 mmol/L, respectively. The predicted decolorization rate under the optimum conditions as determined by the proposed model was 99.55%. Confirmatory tests were carried out and the decolorization rate of 99.49% was observed under the optimum conditions, which agreed well with the model prediction.
In this study, Fe3O4 nanoparticles (Fe3O4 NPs) were successfully prepared via oxidation-precipitation method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The characterization results indicated that Fe3O4 NPs with regular crystal structure and a narrow of diameters had been synthesized successfully and had high purity. A series of experiments were carried out to investigate the degradation of Orange Ⅱ by the obtained heterogeneous Fe3O4 catalysts in the presence of H2O2. The response surface methodology (RSM) based on Box-Behnken design (BBD) was employed to design and optimize individual and interactive effects of the four main independent parameters (catalyst loading, initial pH, reaction temperature and H2O2 concentration) on decolorization efficiency of Orange Ⅱ. A significant quadratic model (p-value <0.0001, R2=0.9369) was derived using analysis of variance (ANOVA). Optimum conditions were catalyst loading of 1.5 g/L, initial pH of 2.7, reaction temperature of 42℃ and H2O2 concentration of 22 mmol/L, respectively. The predicted decolorization rate under the optimum conditions as determined by the proposed model was 99.55%. Confirmatory tests were carried out and the decolorization rate of 99.49% was observed under the optimum conditions, which agreed well with the model prediction.
2014, 25(11): 1461-1465
doi: 10.1016/j.cclet.2014.05.050
Abstract:
The effect of the amount of precipitant ammonia on the Cu0/Cu+ ratio of Cu/SiO2 prepared by the deposition-precipitation method is investigated. Species at different preparation stages, resulted from the amount of ammonia used, are identified by the XRD and FTIR techniques. Chrysocolla together with either copper nitrate hydroxide or copper hydroxide coexist in the uncalcined catalysts. Upon calcination, the latter two species are converted to CuO particles while chrysocolla remains. Following reduction, CuO is transformed to metallic Cu and chrysocolla is converted to Cu2O. The value of Cu0/Cu+ ratio can be evaluated using the peak areas in their TPR profiles. Hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) shows that the selectivity of EG depends on the Cu0/Cu+ ratio. Catalyst prepared with the addition of ammonia solution at n(NH3)/n(Cu2+)=0.9 for precipitation-deposition gains a more suitable Cu0/Cu+ ratio upon reduction and thus has a higher selectivity for EG.
The effect of the amount of precipitant ammonia on the Cu0/Cu+ ratio of Cu/SiO2 prepared by the deposition-precipitation method is investigated. Species at different preparation stages, resulted from the amount of ammonia used, are identified by the XRD and FTIR techniques. Chrysocolla together with either copper nitrate hydroxide or copper hydroxide coexist in the uncalcined catalysts. Upon calcination, the latter two species are converted to CuO particles while chrysocolla remains. Following reduction, CuO is transformed to metallic Cu and chrysocolla is converted to Cu2O. The value of Cu0/Cu+ ratio can be evaluated using the peak areas in their TPR profiles. Hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG) shows that the selectivity of EG depends on the Cu0/Cu+ ratio. Catalyst prepared with the addition of ammonia solution at n(NH3)/n(Cu2+)=0.9 for precipitation-deposition gains a more suitable Cu0/Cu+ ratio upon reduction and thus has a higher selectivity for EG.
2014, 25(11): 1466-1468
doi: 10.1016/j.cclet.2014.05.044
Abstract:
A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give α-alkylated carboxylic acids in good yield and in almost enatiomerically pure form.
A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give α-alkylated carboxylic acids in good yield and in almost enatiomerically pure form.
2014, 25(11): 1469-1472
doi: 10.1016/j.cclet.2014.05.022
Abstract:
Twelve novel dithiocarbamates containing 1,2,3-trizaoles group were prepared via one step starting from organic halides, dithiocarbamic acid prop-2-ynyl ester, and sodium azide, using a very simple catalytic system composed of copper(Ⅰ) chloride and water at 70℃. The structures of the new compounds were characterized and screened for their in vitro anti-tumor. Four of the compounds displayed varying levels of anti-tumor activity against the CDC25B.
Twelve novel dithiocarbamates containing 1,2,3-trizaoles group were prepared via one step starting from organic halides, dithiocarbamic acid prop-2-ynyl ester, and sodium azide, using a very simple catalytic system composed of copper(Ⅰ) chloride and water at 70℃. The structures of the new compounds were characterized and screened for their in vitro anti-tumor. Four of the compounds displayed varying levels of anti-tumor activity against the CDC25B.
2014, 25(11): 1473-1478
doi: 10.1016/j.cclet.2014.06.003
Abstract:
Thin films of Cu2-xS (x=0, 1) were deposited on self-assembled, monolayer modified substrates in the copper-thiosulfate system with various concentrations of ethylene diamine tetraacetic acid (EDTA) at a low temperature of 70℃. The thin films were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The optical and photoelectrochemical (PEC) properties of the Cu2-xS semiconductor films were investigated by ultraviolet-visible (UV-vis) absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2-xS nanocrystals formation and growth. The compositions of the Cu2-xS nanocrystals varied from Cu2S (chalcocide) to CuS (covellite) through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2-xS films. The growth mechanisms of Cu2-xS nanocrystals with different EDTA concentrations are proposed and discussed in detail.
Thin films of Cu2-xS (x=0, 1) were deposited on self-assembled, monolayer modified substrates in the copper-thiosulfate system with various concentrations of ethylene diamine tetraacetic acid (EDTA) at a low temperature of 70℃. The thin films were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). The optical and photoelectrochemical (PEC) properties of the Cu2-xS semiconductor films were investigated by ultraviolet-visible (UV-vis) absorption spectroscopy and a three-electrode system. It is found that EDTA plays a key role in the process of Cu2-xS nanocrystals formation and growth. The compositions of the Cu2-xS nanocrystals varied from Cu2S (chalcocide) to CuS (covellite) through adjusting the concentration of EDTA, which is used as a complexing agent to yield high-quality Cu2-xS films. The growth mechanisms of Cu2-xS nanocrystals with different EDTA concentrations are proposed and discussed in detail.
2014, 25(11): 1479-1484
doi: 10.1016/j.cclet.2014.06.023
Abstract:
Enantioselective chlorination of β-keto esters and amides catalyzed by squaramide-linked bisoxazoline ligand-Cu(OAc)2 complexes was investigated. The corresponding chlorinated products were obtained in excellent yields with moderate enantioselectivities. The effect of solvent, temperature, Lewis acid, and ligand structure on the reaction is discussed. This was the first investigation of catalytic asymmetric α-chlorination of β-keto amides. This study has highlighted that a simple chiral squaramide-oxazoline with cheap Cu(OAc)2·H2O complexes can catalyze this chlorination.
Enantioselective chlorination of β-keto esters and amides catalyzed by squaramide-linked bisoxazoline ligand-Cu(OAc)2 complexes was investigated. The corresponding chlorinated products were obtained in excellent yields with moderate enantioselectivities. The effect of solvent, temperature, Lewis acid, and ligand structure on the reaction is discussed. This was the first investigation of catalytic asymmetric α-chlorination of β-keto amides. This study has highlighted that a simple chiral squaramide-oxazoline with cheap Cu(OAc)2·H2O complexes can catalyze this chlorination.
2014, 25(11): 1485-1488
doi: 10.1016/j.cclet.2014.06.001
Abstract:
A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood (pine wood (PW)), hardwoods (poplar wood, catalpa bungi, and Chinese parasol), and agricultural wastes (rice straw, wheat straw, and corn stover (CS)) were exploited. Results showed that the best pretreatment effect was in PW with 54.3% and 31.7% dissolution and extraction ratios, respectively. The crystal form of cellulose in PW extract transformed from I to Ⅱ, and the contended cellulose ratio and glucose conversion ratio reached 85.1% and 85.4%, respectively. CS after steam explosion achieved a similar pretreating effect as PW, with its cellulose hydrolysis ratio reaching as high as 91.5% after IL pretreatment.
A simple and efficient method of enhancing biomass saccharification by microwave-assisted pretreatment with dimethyl sulfoxide/1-allyl-3-methylimidazolium chloride is proposed. Softwood (pine wood (PW)), hardwoods (poplar wood, catalpa bungi, and Chinese parasol), and agricultural wastes (rice straw, wheat straw, and corn stover (CS)) were exploited. Results showed that the best pretreatment effect was in PW with 54.3% and 31.7% dissolution and extraction ratios, respectively. The crystal form of cellulose in PW extract transformed from I to Ⅱ, and the contended cellulose ratio and glucose conversion ratio reached 85.1% and 85.4%, respectively. CS after steam explosion achieved a similar pretreating effect as PW, with its cellulose hydrolysis ratio reaching as high as 91.5% after IL pretreatment.
2014, 25(11): 1489-1491
doi: 10.1016/j.cclet.2014.07.001
Abstract:
Formaldehyde (HCHO) is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measures. The objective of this work is to distinguish between primary and secondary sources of HCHO. Based on about one month of online measurements in winter in Ziyang, Sichuan, the multi-linear regression analysis of ambient concentrations of HCHO and possible tracers (acetonitrile, propane and peroxyacetyl nitrate) was performed. The results show that during winter in Ziyang, biomass burning contributed an average of 53.2% to ambient HCHO levels, while secondary processes contributed about 30.1%, and vehicular sources accounted for 7.1%.
Formaldehyde (HCHO) is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measures. The objective of this work is to distinguish between primary and secondary sources of HCHO. Based on about one month of online measurements in winter in Ziyang, Sichuan, the multi-linear regression analysis of ambient concentrations of HCHO and possible tracers (acetonitrile, propane and peroxyacetyl nitrate) was performed. The results show that during winter in Ziyang, biomass burning contributed an average of 53.2% to ambient HCHO levels, while secondary processes contributed about 30.1%, and vehicular sources accounted for 7.1%.
2014, 25(11): 1492-1494
doi: 10.1016/j.cclet.2014.06.015
Abstract:
A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples. The 2,4-dinitrophenol imprinted polymers exhibited highly selective recognition for the template molecule and the maximum adsorption capacity was 138.9 μg/g. The results indicated that when water is used as the loading solution, only 2,4-dinitrophenol could be adsorbed on the spin column without the remaining structural analogs (2-nitrophenol, 4-nitrophenol and phenol). After eluting with acetonitrile/acetic acid (9/1, v/v), 2,4-dinitrophenol in serum samples could be determined by using the fluorescence spectrometer, based on the fluorescence enhancement of fluorescein by the template molecule. Under the optimal conditions, the spiked recovery ranged from 95.8% to 103.4% and the detection limit was 1 nmol/L. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.
A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples. The 2,4-dinitrophenol imprinted polymers exhibited highly selective recognition for the template molecule and the maximum adsorption capacity was 138.9 μg/g. The results indicated that when water is used as the loading solution, only 2,4-dinitrophenol could be adsorbed on the spin column without the remaining structural analogs (2-nitrophenol, 4-nitrophenol and phenol). After eluting with acetonitrile/acetic acid (9/1, v/v), 2,4-dinitrophenol in serum samples could be determined by using the fluorescence spectrometer, based on the fluorescence enhancement of fluorescein by the template molecule. Under the optimal conditions, the spiked recovery ranged from 95.8% to 103.4% and the detection limit was 1 nmol/L. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.
2014, 25(11): 1495-1498
doi: 10.1016/j.cclet.2014.05.024
Abstract:
A facile, one-pot synthesis of new phenanthridine derivatives by a three-component reaction between phenantridine, dialkyl acetylenedicarboxylates (DAADs), and aromatic aldehydes is described. The reaction is characterized by mild conditions, high selectivity, and tolerance to various functional groups.
A facile, one-pot synthesis of new phenanthridine derivatives by a three-component reaction between phenantridine, dialkyl acetylenedicarboxylates (DAADs), and aromatic aldehydes is described. The reaction is characterized by mild conditions, high selectivity, and tolerance to various functional groups.
2014, 25(11): 1499-1502
doi: 10.1016/j.cclet.2014.05.019
Abstract:
We present here an efficient green process for the synthesis of 1,2,4-thiadiazoles via iodine-catalyzed, oxidative dimerization of thioamides in water using molecular oxygen as a terminal oxidant. Under the optimized reaction conditions, aryl thioamides produced 3,5-diaryl-1,2,4-thiadiazoles in good to excellent yields. Alkyl thioamides and substituted thioureas could also provide corresponding 1,2,4- thiadiazole products.
We present here an efficient green process for the synthesis of 1,2,4-thiadiazoles via iodine-catalyzed, oxidative dimerization of thioamides in water using molecular oxygen as a terminal oxidant. Under the optimized reaction conditions, aryl thioamides produced 3,5-diaryl-1,2,4-thiadiazoles in good to excellent yields. Alkyl thioamides and substituted thioureas could also provide corresponding 1,2,4- thiadiazole products.
2014, 25(11): 1503-1506
doi: 10.1016/j.cclet.2014.06.012
Abstract:
Tetrahydro-β-carbolines with strictosamide skeleton have been synthesized via intermolecular condensation, selective reduction, and intramolecular cyclization starting from phthalic anhydrides and tryptamine. The reactions are carried out undermild conditions with a wide range of substrates and functional groups.
Tetrahydro-β-carbolines with strictosamide skeleton have been synthesized via intermolecular condensation, selective reduction, and intramolecular cyclization starting from phthalic anhydrides and tryptamine. The reactions are carried out undermild conditions with a wide range of substrates and functional groups.
2014, 25(11): 1507-1510
doi: 10.1016/j.cclet.2014.06.013
Abstract:
A simple synthetic protocol has been developed involving the three-component reaction between 1,2-diamines, ethyl pyruvate and α-bromo ketones in the presence of FeCl3 as a catalyst. A number of pyrrolo[1,2-a]quinoxaline and pyrrolo[1,2-a]pyrazine derivatives were synthesized in excellent yields using this protocol.
A simple synthetic protocol has been developed involving the three-component reaction between 1,2-diamines, ethyl pyruvate and α-bromo ketones in the presence of FeCl3 as a catalyst. A number of pyrrolo[1,2-a]quinoxaline and pyrrolo[1,2-a]pyrazine derivatives were synthesized in excellent yields using this protocol.
