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2008 Volume 19 Issue 3
2008, 19(3): 253-255
doi: 10.1016/j.cclet.2007.12.025
Abstract:
An isoquinoline-3-carboxylate compound 3 was obtained with a moderate yield of 40% when N-acetyl-(3'-hydroxy-4'-methoxy-5'-methyl) phenylalanine methyl ester 1 was refluxed in HMTA/TFA. However, the anticipated product N-acetyl-(3'-hydroxy-4'-methoxy-5'-methyl-6'-formyl) phenylalanine methyl ester 2 could not be found. The possible mechanism was discussed in this article.
An isoquinoline-3-carboxylate compound 3 was obtained with a moderate yield of 40% when N-acetyl-(3'-hydroxy-4'-methoxy-5'-methyl) phenylalanine methyl ester 1 was refluxed in HMTA/TFA. However, the anticipated product N-acetyl-(3'-hydroxy-4'-methoxy-5'-methyl-6'-formyl) phenylalanine methyl ester 2 could not be found. The possible mechanism was discussed in this article.
2008, 19(3): 256-258
doi: 10.1016/j.cclet.2008.01.009
Abstract:
Dihydromayurone (3), a key intermediate to synthesize (-)-thujopsene (1), was efficient enantiocontrolled synthesized from (+)-dihydrocarvone through 9 steps in an overall yield of 19.3%. The key step was the Simmons-Smith reaction.
Dihydromayurone (3), a key intermediate to synthesize (-)-thujopsene (1), was efficient enantiocontrolled synthesized from (+)-dihydrocarvone through 9 steps in an overall yield of 19.3%. The key step was the Simmons-Smith reaction.
2008, 19(3): 259-260
doi: 10.1016/j.cclet.2007.12.018
Abstract:
The synthesis of 14-epi-19-nor-22-oxa-1α, 25(OH)2D3 5 was started from diol 8 via Fall's method, oxidation, epimerization, protection, coupling with the 19-nor-A-ring 7, and then deprotection of the hydroxyl functions.
The synthesis of 14-epi-19-nor-22-oxa-1α, 25(OH)2D3 5 was started from diol 8 via Fall's method, oxidation, epimerization, protection, coupling with the 19-nor-A-ring 7, and then deprotection of the hydroxyl functions.
2008, 19(3): 261-263
doi: 10.1016/j.cclet.2007.12.027
Abstract:
A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1, 3-diphenylprop-2-en-1-yl pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.
A novel chiral phosphine-triazine ligand was synthesized from chiral α-phenylethylamine through a three-step procedure. In a model reaction of Pd-catalyzed allylic alkylation of rac-1, 3-diphenylprop-2-en-1-yl pivalate with dimethyl malonate, good enantioselectivity (90% e.e.) was obtained by using this ligand.
2008, 19(3): 264-268
doi: 10.1016/j.cclet.2007.12.031
Abstract:
Novel chiral tetralin compounds were designed and synthesized, and their antifungal activities in vitro were tested. The results showed that all of target compounds had potent antifungal activities, and were stronger than that of control compounds tetrahydroisoquinolines. The binding model of lead molecules in the active site of CYP51 of Candida albicans showed that lead compound specifically interacted with the amino acids residues in the active site, without binding with the heme of CYP51, which was different from azole antifungal drugs. The present study might afford a novel lead molecule to develop non-azole CYP51 inhibitors of fungi.
Novel chiral tetralin compounds were designed and synthesized, and their antifungal activities in vitro were tested. The results showed that all of target compounds had potent antifungal activities, and were stronger than that of control compounds tetrahydroisoquinolines. The binding model of lead molecules in the active site of CYP51 of Candida albicans showed that lead compound specifically interacted with the amino acids residues in the active site, without binding with the heme of CYP51, which was different from azole antifungal drugs. The present study might afford a novel lead molecule to develop non-azole CYP51 inhibitors of fungi.
2008, 19(3): 269-272
doi: 10.1016/j.cclet.2008.01.003
Abstract:
A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and analogues could be obtained easily.
A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and analogues could be obtained easily.
2008, 19(3): 273-276
doi: 10.1016/j.cclet.2007.12.020
Abstract:
Axially substituted tin phthalocyanines, namely dichloride-tetra-(α-pentyloxy) tin (IV) phthalocyanine 2, dihydroxy-tetra-(α-pentyloxy) tin (IV) phthalocyanine 3 and its dimmer di-μ-oxo-tetra-(α-pentyloxy) tin (IV) phthalocyanine 4 were synthesized. The catalytic effect of H2O-free CaCl2 in quinoline was used for condensation of dihydroxy tin phthalocyanine 3 to the cofacially arraydimmer 4. Their structures were characterized by UV-vis, IR, elemental analysis, MS, as well as 1HNMR spectroscopy.
Axially substituted tin phthalocyanines, namely dichloride-tetra-(α-pentyloxy) tin (IV) phthalocyanine 2, dihydroxy-tetra-(α-pentyloxy) tin (IV) phthalocyanine 3 and its dimmer di-μ-oxo-tetra-(α-pentyloxy) tin (IV) phthalocyanine 4 were synthesized. The catalytic effect of H2O-free CaCl2 in quinoline was used for condensation of dihydroxy tin phthalocyanine 3 to the cofacially arraydimmer 4. Their structures were characterized by UV-vis, IR, elemental analysis, MS, as well as 1HNMR spectroscopy.
2008, 19(3): 277-278
doi: 10.1016/j.cclet.2007.12.022
Abstract:
A novel phosphorus-nitrogen containing intumescent flame retardant (P-N IFR) was prepared via the reaction of dichloropentate with N-methylaniline. The structure of the product was confirmed by 1H NMR, 31P NMR, MS and IR. TGA analysis showed it has effective thermal stability.
A novel phosphorus-nitrogen containing intumescent flame retardant (P-N IFR) was prepared via the reaction of dichloropentate with N-methylaniline. The structure of the product was confirmed by 1H NMR, 31P NMR, MS and IR. TGA analysis showed it has effective thermal stability.
2008, 19(3): 279-280
doi: 10.1016/j.cclet.2008.01.012
Abstract:
(R)-1-(4-Methoxyphenyl) propan-2-amine 2a, an optical active intermediate for (R,R)-formoterol, was synthesized from D-alanine in 65% overall yield by using a simple route, which contained protecting amino group, cyclization, coupling with Grignard reagent, reduction and deprotection.
(R)-1-(4-Methoxyphenyl) propan-2-amine 2a, an optical active intermediate for (R,R)-formoterol, was synthesized from D-alanine in 65% overall yield by using a simple route, which contained protecting amino group, cyclization, coupling with Grignard reagent, reduction and deprotection.
2008, 19(3): 281-285
doi: 10.1016/j.cclet.2007.12.035
Abstract:
Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues (1A-1C, 1E) with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26 cell lines, and analogue 1A and 1C exhibited more potent cytotoxicity than curcumin against CT26 cell line. It was suggested that introduction of appropriate substituents to 4-position of phenyl group might be a potential option for structural modification of curcumin.
Five novel curcumin analogues bearing different substituents at 4-position of phenyl group were synthesized. Their structures were confirmed by NMR and HRMS spectrum. Their cytotoxic activities against six tumor cell lines were tested by the standard MTT assay in vitro. The results indicated that four analogues (1A-1C, 1E) with solubilizing moieties showed selective potent cytotoxicity against HepG2, HeLa and CT26 cell lines, and analogue 1A and 1C exhibited more potent cytotoxicity than curcumin against CT26 cell line. It was suggested that introduction of appropriate substituents to 4-position of phenyl group might be a potential option for structural modification of curcumin.
2008, 19(3): 286-290
doi: 10.1016/j.cclet.2007.12.033
Abstract:
A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate (DMC) synthesis by the transesterification of propylene carbonate (PC) with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products.
A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate (DMC) synthesis by the transesterification of propylene carbonate (PC) with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products.
2008, 19(3): 291-294
doi: 10.1016/j.cclet.2008.01.015
Abstract:
The design, synthesis and biological evaluation of a novel series of arylpiperazine derivatives of diphenylsulfide with dual 5-HT1A/SSRI activities are reported. The target compounds exhibit low to moderate 5-HT transporter affinity and moderate to high 5-HT1A affinity. Compound 13a shows moderate dual activities and is a promising lead compound for further structure-activity relationships studies.
The design, synthesis and biological evaluation of a novel series of arylpiperazine derivatives of diphenylsulfide with dual 5-HT1A/SSRI activities are reported. The target compounds exhibit low to moderate 5-HT transporter affinity and moderate to high 5-HT1A affinity. Compound 13a shows moderate dual activities and is a promising lead compound for further structure-activity relationships studies.
2008, 19(3): 295-298
doi: 10.1016/j.cclet.2008.01.016
Abstract:
The design, synthesis and biological evaluation of N-(2-(2-methoxyphenylthio) benzyl)-2-aryloxyethyl amines with dual 5-HT1A/SSRI activities are reported. Compound 8e displays the best dual activities and is a promising lead compound for further SAR studies.
The design, synthesis and biological evaluation of N-(2-(2-methoxyphenylthio) benzyl)-2-aryloxyethyl amines with dual 5-HT1A/SSRI activities are reported. Compound 8e displays the best dual activities and is a promising lead compound for further SAR studies.
2008, 19(3): 299-301
doi: 10.1016/j.cclet.2007.12.019
Abstract:
Cunninghamella elegans has been employed for the biotransformation of cinobufagin (1) to afford one metabolites. The structure of the transformation product has been characterized as 7β, 12β-dihydroxylcinobufagin (2). Product 2 is a new compound. In vitro cytotoxic activities of the biotransformation product and the substrate-cinobufagin have been assayed against HeLa; they all showed cytotoxic activities.
Cunninghamella elegans has been employed for the biotransformation of cinobufagin (1) to afford one metabolites. The structure of the transformation product has been characterized as 7β, 12β-dihydroxylcinobufagin (2). Product 2 is a new compound. In vitro cytotoxic activities of the biotransformation product and the substrate-cinobufagin have been assayed against HeLa; they all showed cytotoxic activities.
2008, 19(3): 302-304
doi: 10.1016/j.cclet.2008.01.007
Abstract:
(3S)-2-Oxo-5, 12-dimethoxy-3-hydroxy-3-methylbenz[f]indoline (1), a new benzoxindole alkaloid, along with two known alkaloids, was isolated from the root barks of Goniothalamus cheliensis Hu. The structure was elucidated by spectroscopic evidences, and the absolute configuration was determined by CD spectrum.
(3S)-2-Oxo-5, 12-dimethoxy-3-hydroxy-3-methylbenz[f]indoline (1), a new benzoxindole alkaloid, along with two known alkaloids, was isolated from the root barks of Goniothalamus cheliensis Hu. The structure was elucidated by spectroscopic evidences, and the absolute configuration was determined by CD spectrum.
2008, 19(3): 305-307
doi: 10.1016/j.cclet.2007.12.034
Abstract:
A new triterpenoid bisglycoside, named raddeanoside R19, was isolated from the roots of Anemone raddeana. Its structure was elucidated on the basis of ESI-MS, 13C NMR, and chemical methods.
A new triterpenoid bisglycoside, named raddeanoside R19, was isolated from the roots of Anemone raddeana. Its structure was elucidated on the basis of ESI-MS, 13C NMR, and chemical methods.
2008, 19(3): 308-310
doi: 10.1016/j.cclet.2008.01.013
Abstract:
A new benzylisoquinoline alkaloid, named nelumstemine (1), 1-(4'-hydroxybenzoyl)-6, 7-dimethoxy-3, 4-dihydroisoquinoline, was isolated from the stems of Nelumbo nucifera Geartn. Its structure was established on the basis of spectral analysis.
A new benzylisoquinoline alkaloid, named nelumstemine (1), 1-(4'-hydroxybenzoyl)-6, 7-dimethoxy-3, 4-dihydroisoquinoline, was isolated from the stems of Nelumbo nucifera Geartn. Its structure was established on the basis of spectral analysis.
2008, 19(3): 311-313
doi: 10.1016/j.cclet.2008.01.005
Abstract:
By the addition of rice wine koji, enhancement of the reactivity was observed for the baker's yeast reduction of b-keto esters into (S)-β-hydroxy esters with high enantiomeric purity (73-98%).
By the addition of rice wine koji, enhancement of the reactivity was observed for the baker's yeast reduction of b-keto esters into (S)-β-hydroxy esters with high enantiomeric purity (73-98%).
2008, 19(3): 314-318
doi: 10.1016/j.cclet.2007.12.030
Abstract:
A new amperometric biosensor for hydrogen peroxide was developed based on adsorption of horseradish peroxidase at the glassy carbon electrode modified with zinc oxide nanoflowers produced by electrodeposition onto multi-walled carbon nanotubes (MWNTs) film. The morphology of the MWNTs/nano-ZnO electrode has been investigated by scanning electron microscopy (SEM), and the electrochemical performance of the electrode has also been studied by amperometric method. The resulting electrode offered an excellent detection for hydrogen peroxide at -0.11 V with a linear response range of 9.9×10-7 to 2.9×10-3 mol/L with a correlation coefficient of 0.991, and response time < 5 s. The biosensor displays rapid response and expanded linear response range, and excellent stability.
A new amperometric biosensor for hydrogen peroxide was developed based on adsorption of horseradish peroxidase at the glassy carbon electrode modified with zinc oxide nanoflowers produced by electrodeposition onto multi-walled carbon nanotubes (MWNTs) film. The morphology of the MWNTs/nano-ZnO electrode has been investigated by scanning electron microscopy (SEM), and the electrochemical performance of the electrode has also been studied by amperometric method. The resulting electrode offered an excellent detection for hydrogen peroxide at -0.11 V with a linear response range of 9.9×10-7 to 2.9×10-3 mol/L with a correlation coefficient of 0.991, and response time < 5 s. The biosensor displays rapid response and expanded linear response range, and excellent stability.
2008, 19(3): 319-323
doi: 10.1016/j.cclet.2007.12.017
Abstract:
The similar electrochemical oxidation behaviors of hydroxypivalaldehyde in ionic liquids (ILs) medium, C4MIMPF6, C4MIMBF4 and C8MIMPF6, are investigated using classic electrochemical methods, respectively. Only the product, hydroxypivalic acid is detected by high performance liquid chromatography (HPLC). It can be conferred that the electrochemical oxidation of hydroxypivalaldehyde consists of two successive one-electron irreversible reactions at glass carbon (GC) electrode and the possible reaction mechanism in the ILs is proposed firstly. The diffusion coefficients of hydroxypivalaldehyde are obtained according to the electrochemical characteristics of hydroxypivalaldehyde in C4MIMPF6, C4MIMBF4 and C8MIMPF6.
The similar electrochemical oxidation behaviors of hydroxypivalaldehyde in ionic liquids (ILs) medium, C4MIMPF6, C4MIMBF4 and C8MIMPF6, are investigated using classic electrochemical methods, respectively. Only the product, hydroxypivalic acid is detected by high performance liquid chromatography (HPLC). It can be conferred that the electrochemical oxidation of hydroxypivalaldehyde consists of two successive one-electron irreversible reactions at glass carbon (GC) electrode and the possible reaction mechanism in the ILs is proposed firstly. The diffusion coefficients of hydroxypivalaldehyde are obtained according to the electrochemical characteristics of hydroxypivalaldehyde in C4MIMPF6, C4MIMBF4 and C8MIMPF6.
2008, 19(3): 324-328
doi: 10.1016/j.cclet.2007.12.008
Abstract:
A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry (ESI-MSn) conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the multiple tandem mass spectra of four compounds, and the structures of which are identical except for some substituted groups or epimers or cis-trans-isomers. Attempts have been made to provide rational pathways for the formation of the fragment ions from these protonated compounds. And the structure-fragmentation relationships will facilitate the characterization of the structures of other analogs.
A detailed analysis of benzofuranone compounds under multiple tandem mass spectrometry (ESI-MSn) conditions is reported. Element composition data of the fragment ions were obtained with the aid of comparison of the multiple tandem mass spectra of four compounds, and the structures of which are identical except for some substituted groups or epimers or cis-trans-isomers. Attempts have been made to provide rational pathways for the formation of the fragment ions from these protonated compounds. And the structure-fragmentation relationships will facilitate the characterization of the structures of other analogs.
2008, 19(3): 329-332
doi: 10.1016/j.cclet.2008.01.018
Abstract:
In this paper, a sensitive and specific liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and determination of seven flavonoids, namely epimedin A, epimedin B, epimedin C, icariin, sagittatoside B, 2"-O-rhamnosyl icariside II, and baohuoside I in Epimedium from different sources.
In this paper, a sensitive and specific liquid chromatography-electrospray ionisation-mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and determination of seven flavonoids, namely epimedin A, epimedin B, epimedin C, icariin, sagittatoside B, 2"-O-rhamnosyl icariside II, and baohuoside I in Epimedium from different sources.
2008, 19(3): 333-336
doi: 10.1016/j.cclet.2007.12.021
Abstract:
Dimethoxyphenol was a widely used substrate in determination of laccases activity. It was surprised, however, that the products of it had not been completely determined until now. Studies were thus conducted on Rhus laccase (RL) and immobilized Rhus laccase (IRL)-catalyzed oxidation of 2, 6-dimethoxyphenol (DMP) in water-organic solvent systems. Only one product, 3, 3', 5, 5'-tetramethoxy-1, 1'-biphenyl-4, 4'-diol (TMBP), was produced by RL catalysis, and it was thoroughly characterized by FT-IR, NMR and GC-MS, etc.
Dimethoxyphenol was a widely used substrate in determination of laccases activity. It was surprised, however, that the products of it had not been completely determined until now. Studies were thus conducted on Rhus laccase (RL) and immobilized Rhus laccase (IRL)-catalyzed oxidation of 2, 6-dimethoxyphenol (DMP) in water-organic solvent systems. Only one product, 3, 3', 5, 5'-tetramethoxy-1, 1'-biphenyl-4, 4'-diol (TMBP), was produced by RL catalysis, and it was thoroughly characterized by FT-IR, NMR and GC-MS, etc.
2008, 19(3): 338-341
doi: 10.1016/j.cclet.2008.01.001
Abstract:
Composites Li1-xVxCryFe1-yPO4/C (x=0.01, 0.02; y=0.01, 0.02) were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.
Composites Li1-xVxCryFe1-yPO4/C (x=0.01, 0.02; y=0.01, 0.02) were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.
2008, 19(3): 342-344
doi: 10.1016/j.cclet.2007.12.028
Abstract:
As DNA cleavage agent, a new diiron (III) complex (Fe2Lb), in which a DNA-intercalator (pyrene) is covalently linked to a diferric moiety, has been synthesized and characterized. The DNA-binding property and DNA cleavage activity of the complex have also been investigated.
As DNA cleavage agent, a new diiron (III) complex (Fe2Lb), in which a DNA-intercalator (pyrene) is covalently linked to a diferric moiety, has been synthesized and characterized. The DNA-binding property and DNA cleavage activity of the complex have also been investigated.
2008, 19(3): 345-349
doi: 10.1016/j.cclet.2007.10.052
Abstract:
Lithium iron phosphate (LiFePO4) doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge-discharge cycling.The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of glucose. At ambient temperature (28±2℃), the electrochemical performances of LiFePO4 prepared exhibit the high discharge capacity of 135 mAh g-1 at 5C and good capacity retention of 98% over 90 cycles. The excellent electrochemical performances should be correlated with the intimate contact between carbon and LiFePO4 primary and secondary particles, resulting from the in situ formation of carbon precursor/carbon, leading to the increase in conductivity of LiFePO4.
Lithium iron phosphate (LiFePO4) doped with magnesium was hydrothermally synthesized from commercial LiOH, FeSO4, H3PO4 and MgSO4 with glucose as carbon precursor in aqueous solution. The samples were characterized by X-ray powder diffraction, scanning electron microscopy and constant charge-discharge cycling.The results show that the synthesized powders have been in situ coated with carbon precursor produced from caramel reaction of glucose. At ambient temperature (28±2℃), the electrochemical performances of LiFePO4 prepared exhibit the high discharge capacity of 135 mAh g-1 at 5C and good capacity retention of 98% over 90 cycles. The excellent electrochemical performances should be correlated with the intimate contact between carbon and LiFePO4 primary and secondary particles, resulting from the in situ formation of carbon precursor/carbon, leading to the increase in conductivity of LiFePO4.
2008, 19(3): 350-354
doi: 10.1016/j.cclet.2007.11.021
Abstract:
The flame retardant mechanism of the copolyester phosphorus containing linked pendant groups was investigated by thermogravimetric (TG), X-ray photoelectron spectroscopy (XPS) and direct insertion probe pyrolysis mass spectrometry (DPMS) technique. TG results show that the incorporation of phosphorus containing unit linked pendant groups can destabilize the copolyester due to the cleavage of P-CH2 bond, and phosphorus containing units cannot promote the char-formation of the copolyester during the thermal degradation of the copolyester. XPS spectra indicate that with the increase of the temperature, the P-CH2 bonds of the copolyester break down gradually, the concentration of phosphorus in the condensed phase products decrease gradually and the chemical state of phosphorus does not change in the temperature of 250-380℃. Direct pyrolysis MS suggests that the P-CH2 bonds cleavage occurs at pendant groups and species containing phosphorus can volatilize into the gas phase. A flame retardant mechanism is proposed for the gas phase mode of action of the halogen-free copolyester phosphorus containing linked pendant groups.
The flame retardant mechanism of the copolyester phosphorus containing linked pendant groups was investigated by thermogravimetric (TG), X-ray photoelectron spectroscopy (XPS) and direct insertion probe pyrolysis mass spectrometry (DPMS) technique. TG results show that the incorporation of phosphorus containing unit linked pendant groups can destabilize the copolyester due to the cleavage of P-CH2 bond, and phosphorus containing units cannot promote the char-formation of the copolyester during the thermal degradation of the copolyester. XPS spectra indicate that with the increase of the temperature, the P-CH2 bonds of the copolyester break down gradually, the concentration of phosphorus in the condensed phase products decrease gradually and the chemical state of phosphorus does not change in the temperature of 250-380℃. Direct pyrolysis MS suggests that the P-CH2 bonds cleavage occurs at pendant groups and species containing phosphorus can volatilize into the gas phase. A flame retardant mechanism is proposed for the gas phase mode of action of the halogen-free copolyester phosphorus containing linked pendant groups.
2008, 19(3): 355-358
doi: 10.1016/j.cclet.2008.01.008
Abstract:
Novel double hydrophilic block copolymers with amine pendant chains were synthesized by polymerization of 4-vinyl benzylamine hydrochloric salt using 4, 4'-azo-bis[4-cyanopentanoate poly (ethylene glycol) ester] as macroazoinitiator. The structures of the copolymers were characterized by 1H NMR, FTIR spectra and acid-base titration, GPC-MALS techniques.
Novel double hydrophilic block copolymers with amine pendant chains were synthesized by polymerization of 4-vinyl benzylamine hydrochloric salt using 4, 4'-azo-bis[4-cyanopentanoate poly (ethylene glycol) ester] as macroazoinitiator. The structures of the copolymers were characterized by 1H NMR, FTIR spectra and acid-base titration, GPC-MALS techniques.
2008, 19(3): 359-362
doi: 10.1016/j.cclet.2007.12.032
Abstract:
In this study, a novel 4-(4-octyloxybenzoyloxy) biphenyl-3', 5'-diaminobenzoate and polyimides based on it were synthesized.The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal (LC). The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV-vis spectra of the novel polyimide films showed the high transparency in a visible wave length.
In this study, a novel 4-(4-octyloxybenzoyloxy) biphenyl-3', 5'-diaminobenzoate and polyimides based on it were synthesized.The polyimide with mesogenic unit side chain exhibited excellent vertical alignment for nematic liquid crystal (LC). The pretilt angles of LCs above 89° were kept after the rubbing process with 220 mm rubbing strength. The polyimide films as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable. Meanwhile, the UV-vis spectra of the novel polyimide films showed the high transparency in a visible wave length.
2008, 19(3): 363-366
doi: 10.1016/j.cclet.2008.01.004
Abstract:
Copolymerizations of L-lactide (L-LA) and e-caprolactone (ε-CL) were conducted in bulk using magnesium octoate as a catalyst. The reactivity ratios of L-LA and ε-CL were determined to be rL=23 and rC=0.22, respectively. The sequence analyses of the copolymers were performed on 13C NMR. An increase in the reaction temperature enhances the role of transesterification and the extent of randomness.
Copolymerizations of L-lactide (L-LA) and e-caprolactone (ε-CL) were conducted in bulk using magnesium octoate as a catalyst. The reactivity ratios of L-LA and ε-CL were determined to be rL=23 and rC=0.22, respectively. The sequence analyses of the copolymers were performed on 13C NMR. An increase in the reaction temperature enhances the role of transesterification and the extent of randomness.
2008, 19(3): 367-370
doi: 10.1016/j.cclet.2007.12.029
Abstract:
New hydrophobic poly (phthalazinone ether sulfone ketone) (PPESK) hollow fiber composite membranes were obtained by surface-coated modification method.
New hydrophobic poly (phthalazinone ether sulfone ketone) (PPESK) hollow fiber composite membranes were obtained by surface-coated modification method.
2008, 19(3): 371-374
doi: 10.1016/j.cclet.2007.11.007
Abstract:
Environmentally persistent and bioaccumulative perfluorooctanic acid (PFOA) was difficult to be decomposed under the irradiation of 254 nm UV light. However, in the presence of 80 μmol/L Fe (III), 80%of PFOAwith initial concentration of 48 μmol/L (20 mg/L) was effectively degraded and 47.8% of fluorine atoms in PFOA molecule were transformed into inorganic fluoride ion after 4 h reaction. Shorter chain perfluorocarboxylic acids bearing C3-C7 and fluoride ion were detected and identified by LC/MS and IC as the degradation products in the aqueous solution. It was proposed that complexes of PFOA with Fe (III) initiated degradation of PFOA irradiated with 254 nm UV light.
Environmentally persistent and bioaccumulative perfluorooctanic acid (PFOA) was difficult to be decomposed under the irradiation of 254 nm UV light. However, in the presence of 80 μmol/L Fe (III), 80%of PFOAwith initial concentration of 48 μmol/L (20 mg/L) was effectively degraded and 47.8% of fluorine atoms in PFOA molecule were transformed into inorganic fluoride ion after 4 h reaction. Shorter chain perfluorocarboxylic acids bearing C3-C7 and fluoride ion were detected and identified by LC/MS and IC as the degradation products in the aqueous solution. It was proposed that complexes of PFOA with Fe (III) initiated degradation of PFOA irradiated with 254 nm UV light.
2008, 19(3): 375-378
doi: 10.1016/j.cclet.2007.11.030
Abstract:
The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G (d), B3LYP/6-31+G (d, p), and B3LYP/6-311+G (3df, 2p)//B3LYP/6-31+G (d, p) levels to explore the reaction mechanism. According to the mechanism proposed by Kappe, structures of five intermediates were optimized and four transition states were found. The calculation results proved that the mechanism proposed by Kappe is right.
The condensation of benzaldehyde, urea, and ethyl acetoacetate according to the procedure described by Biginelli was investigated at the B3LYP/6-31G (d), B3LYP/6-31+G (d, p), and B3LYP/6-311+G (3df, 2p)//B3LYP/6-31+G (d, p) levels to explore the reaction mechanism. According to the mechanism proposed by Kappe, structures of five intermediates were optimized and four transition states were found. The calculation results proved that the mechanism proposed by Kappe is right.
