Login In
2013 Volume 24 Issue 1
2013, 24(01): 1-6
Abstract:
As one type of promising candidates for environmental and energy-related systems,multi-shelled transition metal oxide hollow structures(MS-TMOHSs)have drawn great scientific and technical interest in the past few years.This article highlights recent advances in one-pot solution synthesis of MS-TMOHSs.We begin it with an overview of synthetic strategies that have been exploited to achieve these peculiar structures.We then focus on one-pot solution approaches in the following four sections:i)soft templates directed growth;ii)Ostwald ripening;iii)controlled etching;and iv)gas bubble assisted growth.After giving a brief discussion on the unique properties and applications of these multi-shelled hollow structures,we conclude this review with the general challenges and the potential future directions of this exciting area of research.
As one type of promising candidates for environmental and energy-related systems,multi-shelled transition metal oxide hollow structures(MS-TMOHSs)have drawn great scientific and technical interest in the past few years.This article highlights recent advances in one-pot solution synthesis of MS-TMOHSs.We begin it with an overview of synthetic strategies that have been exploited to achieve these peculiar structures.We then focus on one-pot solution approaches in the following four sections:i)soft templates directed growth;ii)Ostwald ripening;iii)controlled etching;and iv)gas bubble assisted growth.After giving a brief discussion on the unique properties and applications of these multi-shelled hollow structures,we conclude this review with the general challenges and the potential future directions of this exciting area of research.
2013, 24(01): 7-8
Abstract:
A convenient and scalable synthesis of 1-amino-5-cyanonaphthalene was described.
A convenient and scalable synthesis of 1-amino-5-cyanonaphthalene was described.
2013, 24(01): 9-12
Abstract:
Implantable materials have broad applications in tissue engineering and in vivo sensors.It is essential to know the detailed information of the implantable materials during their degradation.In this paper,we developed a method to monitor the degradation process of a well-used biomaterial,poly(lactide-co-glycolide)(PLGA)by taking advantage of inverse opal structure.We found that mass loss,molecular weight and glass transition temperature of PLGA during the degradation process in Hank's artificial body fluid can be in situ monitored by measuring the optical properties of PLGA inverse opal.
Implantable materials have broad applications in tissue engineering and in vivo sensors.It is essential to know the detailed information of the implantable materials during their degradation.In this paper,we developed a method to monitor the degradation process of a well-used biomaterial,poly(lactide-co-glycolide)(PLGA)by taking advantage of inverse opal structure.We found that mass loss,molecular weight and glass transition temperature of PLGA during the degradation process in Hank's artificial body fluid can be in situ monitored by measuring the optical properties of PLGA inverse opal.
2013, 24(01): 13-16
Abstract:
Linear diribonucleoside phosphotriester is an important intermediate for synthesizing biologically important compounds,such as cyclic bis(3'-5')diguanylic acid(c-di-GMP)and its analogues. Atropisomerism of diastereomers generated by the chiral center of the P atom,which results in the doubling of signals in 31P NMR.The data of 31P NMR at different temperature are presented,and thereafter the reason is discussed.
Linear diribonucleoside phosphotriester is an important intermediate for synthesizing biologically important compounds,such as cyclic bis(3'-5')diguanylic acid(c-di-GMP)and its analogues. Atropisomerism of diastereomers generated by the chiral center of the P atom,which results in the doubling of signals in 31P NMR.The data of 31P NMR at different temperature are presented,and thereafter the reason is discussed.
2013, 24(01): 17-19
Abstract:
A simple and green method is developed to prepare hexagonal boron nitride(h-BN)/poly(vinyl alcohol) (PVA)nanocomposites by using water as a common solvent of h-BN nanosheets and PVA.The obtained h-BN/PVA nanocomposites are highly transparent,and have significantly improved mechanical and thermal properties.They may outperform nano-clay and nano-alumina/PVA nanocomposites as flexible optoelectronic devices,optical windows and heat-releasing materials operated in oxidative or corrosive environment.
A simple and green method is developed to prepare hexagonal boron nitride(h-BN)/poly(vinyl alcohol) (PVA)nanocomposites by using water as a common solvent of h-BN nanosheets and PVA.The obtained h-BN/PVA nanocomposites are highly transparent,and have significantly improved mechanical and thermal properties.They may outperform nano-clay and nano-alumina/PVA nanocomposites as flexible optoelectronic devices,optical windows and heat-releasing materials operated in oxidative or corrosive environment.
2013, 24(01): 20-22
Abstract:
A new metal complex[MnL2](NO3)2·CH3CN(1)was synthesized by reaction of 4'-4-(1,2,4-triazol-1-yl)-phenyl-2,2':6',2"-terpyridine(L)with manganese nitrate.The structure of the complex was determined by X-ray crystallography.The results of UV-vis studies showed that the complex exhibits colorimetric sensing ability for Fe3+,which can be observed by naked eye.
A new metal complex[MnL2](NO3)2·CH3CN(1)was synthesized by reaction of 4'-4-(1,2,4-triazol-1-yl)-phenyl-2,2':6',2"-terpyridine(L)with manganese nitrate.The structure of the complex was determined by X-ray crystallography.The results of UV-vis studies showed that the complex exhibits colorimetric sensing ability for Fe3+,which can be observed by naked eye.
2013, 24(01): 23-27
Abstract:
We report on the effects of aggregation of P3HT with ordered conformation in solution on improving the uniaxial alignment of the P3HT nanofibers by zone casting.Two approaches were employed to change the aggregation of P3HT:P3HT blending with coil insulating polymer and ultrasonic oscillating.The insulator polymer(i.e.PS)which has good solubility in the solution would disturb the aggregation of P3HT to prevent the chains entanglement.The ultrasonic oscillation can further improve the P3HT aggregation with ordered conformation in the solution.As a result,the P3HT nanofibers in the film grew much orientedly by zone casting the ultrasonic oscillating P3HT/PS polymer blends solution than the same solvent P3HT solution without ultrasonic oscillating and blending.The P3HTπ-πstacking direction is parallel to the alignment direction of the nanofibers.Meanwhile,the P3HT/PS blend ratio and PS molecular weight have influence on the uniaxial alignment of P3HT nanofibers.Only P3HT/PS is 1:1, the P3HT nanofibers oriented well.The low molecular weight PS can make the P3HT nanofibers orient better than that of the high molecular weight.
We report on the effects of aggregation of P3HT with ordered conformation in solution on improving the uniaxial alignment of the P3HT nanofibers by zone casting.Two approaches were employed to change the aggregation of P3HT:P3HT blending with coil insulating polymer and ultrasonic oscillating.The insulator polymer(i.e.PS)which has good solubility in the solution would disturb the aggregation of P3HT to prevent the chains entanglement.The ultrasonic oscillation can further improve the P3HT aggregation with ordered conformation in the solution.As a result,the P3HT nanofibers in the film grew much orientedly by zone casting the ultrasonic oscillating P3HT/PS polymer blends solution than the same solvent P3HT solution without ultrasonic oscillating and blending.The P3HTπ-πstacking direction is parallel to the alignment direction of the nanofibers.Meanwhile,the P3HT/PS blend ratio and PS molecular weight have influence on the uniaxial alignment of P3HT nanofibers.Only P3HT/PS is 1:1, the P3HT nanofibers oriented well.The low molecular weight PS can make the P3HT nanofibers orient better than that of the high molecular weight.
2013, 24(01): 28-30
Abstract:
MCM-41 supported heteropoly acids(HPAs)catalysts were synthesized,characterized and their catalytic activity was evaluated in an aza-Michael addition reaction between nitroolefins and benzotriazole in water at room temperature.50 wt%PW/MCM-41 showed the highest activity(up to 96%yield).The catalyst was used in six consecutive experiments without obvious loss of activity, confirming the success of the anchoring process and the catalyst stability.
MCM-41 supported heteropoly acids(HPAs)catalysts were synthesized,characterized and their catalytic activity was evaluated in an aza-Michael addition reaction between nitroolefins and benzotriazole in water at room temperature.50 wt%PW/MCM-41 showed the highest activity(up to 96%yield).The catalyst was used in six consecutive experiments without obvious loss of activity, confirming the success of the anchoring process and the catalyst stability.
2013, 24(01): 31-33
Abstract:
A new kind of thiazole-containing unsymmetrical ortho-diamine monomer,2-amino-5-[4-(2'-aminophenoxy)phenyl]-thiazole(o-AAPPT),was synthesized by four steps,using 4-hydroxyacetophe-none as starting material.A novel thiazole-containing polyimide was prepared from the resulting diamine o-AAPPT with BTDA via a conventional one-step method.The resulting polyimide exhibits excellent solubility,film-forming capability and high thermal and thermo-oxidative stability.
A new kind of thiazole-containing unsymmetrical ortho-diamine monomer,2-amino-5-[4-(2'-aminophenoxy)phenyl]-thiazole(o-AAPPT),was synthesized by four steps,using 4-hydroxyacetophe-none as starting material.A novel thiazole-containing polyimide was prepared from the resulting diamine o-AAPPT with BTDA via a conventional one-step method.The resulting polyimide exhibits excellent solubility,film-forming capability and high thermal and thermo-oxidative stability.
2013, 24(01): 34-36
Abstract:
Nanocrystalline TiO2-HClO4,as newly reported catalyst,has been used as an efficient and reusable catalyst for the chemoselective N-Boc protection of amines.The clean,mild acidity condition, quantitative yields of products,short reaction time and low reaction temperature are attractive features of this reaction.In practice,this method is a combination of a satisfactory synthesis and more significantly easy product isolation and purification.
Nanocrystalline TiO2-HClO4,as newly reported catalyst,has been used as an efficient and reusable catalyst for the chemoselective N-Boc protection of amines.The clean,mild acidity condition, quantitative yields of products,short reaction time and low reaction temperature are attractive features of this reaction.In practice,this method is a combination of a satisfactory synthesis and more significantly easy product isolation and purification.
2013, 24(01): 37-40
Abstract:
In order to investigate the effects on the cytotoxicity of indole-3-oxalylamino podophyllotoxin analogs, seven novel podophyllotoxin derivatives were synthesized.The compounds were tested against Hela, K562 or K562/A02 cancer cells in vitro,four of which showed significant cytotoxicity.Among them 9a,9b and 9c were superior to the positive control VP-16.
In order to investigate the effects on the cytotoxicity of indole-3-oxalylamino podophyllotoxin analogs, seven novel podophyllotoxin derivatives were synthesized.The compounds were tested against Hela, K562 or K562/A02 cancer cells in vitro,four of which showed significant cytotoxicity.Among them 9a,9b and 9c were superior to the positive control VP-16.
2013, 24(01): 41-44
Abstract:
Palladium-catalyzed cross-coupling reaction between dichlorotriazines and phenylboronate esters produced the mono-arylated triazines selectively and thus,the corresponding phenyltriazine derivatives could be assembled efficiently in moderate to good overall yields(50-80%).
Palladium-catalyzed cross-coupling reaction between dichlorotriazines and phenylboronate esters produced the mono-arylated triazines selectively and thus,the corresponding phenyltriazine derivatives could be assembled efficiently in moderate to good overall yields(50-80%).
2013, 24(01): 45-48
Abstract:
An effective approach for the direct benzylhalogenation with in situ generation of hypervalent halides has been developed.A variety of benzyl halides are produced in moderate to excellent yields(up to 99%) with high regioselectivities.UV absorption spectrum is employed to detect the formation of tert-butyl hypoiodite.
An effective approach for the direct benzylhalogenation with in situ generation of hypervalent halides has been developed.A variety of benzyl halides are produced in moderate to excellent yields(up to 99%) with high regioselectivities.UV absorption spectrum is employed to detect the formation of tert-butyl hypoiodite.
2013, 24(01): 49-51
Abstract:
The title complex l-[Cu4Ⅱ(Hvap)2(vap)2(MeOH)2](ClO4)2 1 has been synthesized and characterized by EA, IR,TGA,solid-state CD spectra and X-ray single-crystal analyses(l-H2vap:a Schiff base ligand derived from the condensation of o-vanillin and l-2-amino-3-phenyl-1-propanol).Complex 1 crystallizes in monoclinic system,chiral space group P21 with a=10.4257(18),b=21.695(4),c=15.721(3)Å β=94.443(3)°,V=3545.1(11)Å3,Z=2,Cu4C70H78N4O22Cl2,Mr=1652.42,Dc=1.548 g/cm3, F(0 0 0)=1704 and μ(MoKα)=1.338 mm-1.The final R=0.0682 and wR=0.1420 for 6170 observed reflections with I2δ(I)and R=0.1775 and wR=0.1830 for all data.The structure of complex 1 contains a boat-shaped{Cu4O4}motif.The solid-state CD spectra confirm the chiral nature of complex 1.
The title complex l-[Cu4Ⅱ(Hvap)2(vap)2(MeOH)2](ClO4)2 1 has been synthesized and characterized by EA, IR,TGA,solid-state CD spectra and X-ray single-crystal analyses(l-H2vap:a Schiff base ligand derived from the condensation of o-vanillin and l-2-amino-3-phenyl-1-propanol).Complex 1 crystallizes in monoclinic system,chiral space group P21 with a=10.4257(18),b=21.695(4),c=15.721(3)Å β=94.443(3)°,V=3545.1(11)Å3,Z=2,Cu4C70H78N4O22Cl2,Mr=1652.42,Dc=1.548 g/cm3, F(0 0 0)=1704 and μ(MoKα)=1.338 mm-1.The final R=0.0682 and wR=0.1420 for 6170 observed reflections with I2δ(I)and R=0.1775 and wR=0.1830 for all data.The structure of complex 1 contains a boat-shaped{Cu4O4}motif.The solid-state CD spectra confirm the chiral nature of complex 1.
2013, 24(01): 52-54
Abstract:
A new proline-functionalized fiber catalyst was employed for the first time to catalyze the Knoevenagel condensation reactions between aromatic aldehydes and ethyl cyanoacetate or malononitrile.This fiber catalyst exhibits a high efficiency(0.5-2 mol%of catalyst with yields of 90%-99%)and excellent reusability(up to 20 times)without the need for additional treatments.
A new proline-functionalized fiber catalyst was employed for the first time to catalyze the Knoevenagel condensation reactions between aromatic aldehydes and ethyl cyanoacetate or malononitrile.This fiber catalyst exhibits a high efficiency(0.5-2 mol%of catalyst with yields of 90%-99%)and excellent reusability(up to 20 times)without the need for additional treatments.
2013, 24(01): 55-56
Abstract:
In order to find more biologically active substances,we have carefully investigated the chemical constituents of Pterocypsela elata.One new guaianolide,(4S)-11-methoxycarbonyl-guaiane-1(10),5(6),7(11),8(9)-tetraen-6,12-olide was isolated from the EtOAc extracts of the roots of P.elata. Its structure was elucidated by various spectroscopic methods and confirmed by X-ray crystallographic analysis.
In order to find more biologically active substances,we have carefully investigated the chemical constituents of Pterocypsela elata.One new guaianolide,(4S)-11-methoxycarbonyl-guaiane-1(10),5(6),7(11),8(9)-tetraen-6,12-olide was isolated from the EtOAc extracts of the roots of P.elata. Its structure was elucidated by various spectroscopic methods and confirmed by X-ray crystallographic analysis.
2013, 24(01): 57-58
Abstract:
A new norsesquiterpe alkaloid(1)was isolated from the solid culture of mushroom-forming fungus Flammulina velutipes fermented on rice.The structure of 1 was elucidated by spectroscopic methods.The absolute configuration of C-1 in 1 was determined using the circular dichroism data of their [Rh2(OCOCF3)4]complex.
A new norsesquiterpe alkaloid(1)was isolated from the solid culture of mushroom-forming fungus Flammulina velutipes fermented on rice.The structure of 1 was elucidated by spectroscopic methods.The absolute configuration of C-1 in 1 was determined using the circular dichroism data of their [Rh2(OCOCF3)4]complex.
2013, 24(01): 59-62
Abstract:
A series of diphenyl-sulfide(Ph2S)-immobilized Pd/C catalysts(Pd-Ph2S(x)/C)were prepared using the wetness-impregnation and immobilization method.Pd-Ph2S(x)/C catalysts employed for the hydro-genation of o-chloronitrobenzene showed very high selectivity.The structure of Pd-Ph2S(x)/C with different molar ratio of ligand(x-values)was characterized by XPS and TG-DSC-MS.The results suggest a "saturated''surface ratio of Ph2S/Pd(about 0.3)was formed on the Pd-Ph2S(x)/C catalysts surface.The Ph2S immobilized on the Pd particle is quite stable,and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K.The possible catalytic mechanism of the Pd-Ph2S(x)/C catalyst was also discussed.
A series of diphenyl-sulfide(Ph2S)-immobilized Pd/C catalysts(Pd-Ph2S(x)/C)were prepared using the wetness-impregnation and immobilization method.Pd-Ph2S(x)/C catalysts employed for the hydro-genation of o-chloronitrobenzene showed very high selectivity.The structure of Pd-Ph2S(x)/C with different molar ratio of ligand(x-values)was characterized by XPS and TG-DSC-MS.The results suggest a "saturated''surface ratio of Ph2S/Pd(about 0.3)was formed on the Pd-Ph2S(x)/C catalysts surface.The Ph2S immobilized on the Pd particle is quite stable,and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K.The possible catalytic mechanism of the Pd-Ph2S(x)/C catalyst was also discussed.
2013, 24(01): 63-66
Abstract:
A novel magnetically separable visible-light-photocatalyst,magnetite/N-doped carboxylate-rich carbon spheres(N-MCRCSs),was synthesized by a facile ultrasonic method using the magnetite/carboxylate-rich carbon spheres(MCRCSs)as precursors.N element has been successfully doped into the MCRCSs in a HNO3 aqueous solution via an ultrasonic treatment,which were demonstrated by the FT-IR and XPS.N-MCRCSs exhibit more intensive absorption over MCRCSs in the entire UV and visible region.N-MCRCSs can not only be easily recycled by applying an external magnetic field,but also exhibit powerful visible light photocatalytic activity.
A novel magnetically separable visible-light-photocatalyst,magnetite/N-doped carboxylate-rich carbon spheres(N-MCRCSs),was synthesized by a facile ultrasonic method using the magnetite/carboxylate-rich carbon spheres(MCRCSs)as precursors.N element has been successfully doped into the MCRCSs in a HNO3 aqueous solution via an ultrasonic treatment,which were demonstrated by the FT-IR and XPS.N-MCRCSs exhibit more intensive absorption over MCRCSs in the entire UV and visible region.N-MCRCSs can not only be easily recycled by applying an external magnetic field,but also exhibit powerful visible light photocatalytic activity.
2013, 24(01): 67-69
Abstract:
Near-infrared diffuse reflectance spectroscopy(NIRDRS)has attracted more and more attention in analyzing the components in samples with complex matrices.However,to apply this technique to micro-analysis,there are still some obstacles to overcome such as the low sensitivity and spectral overlapping associated with this approach.A method for fast determination of bovine serum albumin (BSA)in micro-volume samples was studied using NIRDRS with sample spots and chemometric techniques.10 μL of sample spotted on a filter paper substrate was used for the spectral measurements. Quantitative analysis was obtained by partial least squares(PLS)regression with signal processing and variable selection.The results show that the correlation coefficient(R)between the predicted and the reference concentration is 0.9897 and the recoveries are in the range of 87.4%-114.4%for the validation samples in the concentration range of 0.61-8.10 mg/mL.These results suggest that the method has the potential to quickly measure proteins in micro-volume solutions.
Near-infrared diffuse reflectance spectroscopy(NIRDRS)has attracted more and more attention in analyzing the components in samples with complex matrices.However,to apply this technique to micro-analysis,there are still some obstacles to overcome such as the low sensitivity and spectral overlapping associated with this approach.A method for fast determination of bovine serum albumin (BSA)in micro-volume samples was studied using NIRDRS with sample spots and chemometric techniques.10 μL of sample spotted on a filter paper substrate was used for the spectral measurements. Quantitative analysis was obtained by partial least squares(PLS)regression with signal processing and variable selection.The results show that the correlation coefficient(R)between the predicted and the reference concentration is 0.9897 and the recoveries are in the range of 87.4%-114.4%for the validation samples in the concentration range of 0.61-8.10 mg/mL.These results suggest that the method has the potential to quickly measure proteins in micro-volume solutions.
2013, 24(01): 70-72
Abstract:
Composite polymer electrolytes based on poly(ethylene oxide)-polysiloxane/1-butyl-3-methylimida-zolium bis(trifluoromethanesulfonyl)imide/organomontmorillonite(PEO-PDMS/IL/OMMT)were pre-pared and characterized.Addition of both an ionic liquid and OMMT to the polymer base of PEO-PDMS resulted in an increase in ionic conductivity.At room temperature,the ionic conductivity of sample PPB100-OMMT4 was 2.19×10-3S/cm.The composite polymer electrolyte also exhibited high thermal and electrochemical stability and may potentially be applied in lithium batteries.
Composite polymer electrolytes based on poly(ethylene oxide)-polysiloxane/1-butyl-3-methylimida-zolium bis(trifluoromethanesulfonyl)imide/organomontmorillonite(PEO-PDMS/IL/OMMT)were pre-pared and characterized.Addition of both an ionic liquid and OMMT to the polymer base of PEO-PDMS resulted in an increase in ionic conductivity.At room temperature,the ionic conductivity of sample PPB100-OMMT4 was 2.19×10-3S/cm.The composite polymer electrolyte also exhibited high thermal and electrochemical stability and may potentially be applied in lithium batteries.
2013, 24(01): 73-75
Abstract:
The complex[Cd(tfbz)2(phen)]2(1)(tfbz=2,4,5-trifluorobenzoate,phen=1,10-phenanthro-line)was synthesized using trifluorobenzoic acid ligand.The single-crystal structure of 1 has been determined by X-ray crystallography.The packing structure is characterized by the formation of an intricate three-dimensional supramolecular network that depends on the C-H…F,F…F,F(lp)…π(lp=lone pair) interactions.
The complex[Cd(tfbz)2(phen)]2(1)(tfbz=2,4,5-trifluorobenzoate,phen=1,10-phenanthro-line)was synthesized using trifluorobenzoic acid ligand.The single-crystal structure of 1 has been determined by X-ray crystallography.The packing structure is characterized by the formation of an intricate three-dimensional supramolecular network that depends on the C-H…F,F…F,F(lp)…π(lp=lone pair) interactions.
2013, 24(01): 76-78
Abstract:
Fabrication of folate and iron-substituted polyoxometalate[(FeOH2)2SiW10O36]to form nanoparticles (FA-SiWFe2)has been achieved.This inorganic-organic hybrid possesses intrinsic peroxidase-like activity,which could be used in detection of cancer cells in colorimetric multiplexed immunoassay.
Fabrication of folate and iron-substituted polyoxometalate[(FeOH2)2SiW10O36]to form nanoparticles (FA-SiWFe2)has been achieved.This inorganic-organic hybrid possesses intrinsic peroxidase-like activity,which could be used in detection of cancer cells in colorimetric multiplexed immunoassay.
2013, 24(01): 79-81
Abstract:
Near-infrared upconverting NaYF4:Yb3+,Tm3+ nanophosphors modified with poly(acrylic acid)were prepared and characterized by transmission electron microscopy and luminescence spectroscopy.Based on the observed overlap between the emission spectrum of the NaYF4:Yb3+,Tm3+nanophosphors and the absorption spectrum of the gold nanorods,we believe that a new "turn-off" luminescence resonance energy transfer aptamer sensor was constructed for sensing thrombin in near-infrared region.
Near-infrared upconverting NaYF4:Yb3+,Tm3+ nanophosphors modified with poly(acrylic acid)were prepared and characterized by transmission electron microscopy and luminescence spectroscopy.Based on the observed overlap between the emission spectrum of the NaYF4:Yb3+,Tm3+nanophosphors and the absorption spectrum of the gold nanorods,we believe that a new "turn-off" luminescence resonance energy transfer aptamer sensor was constructed for sensing thrombin in near-infrared region.
2013, 24(01): 82-84
Abstract:
Recently,we reported that deoxyribo-oligonucleotides could induce single chained cationic surfactant aggregation to form vesicles.In this paper,we will present that ribo-oligonucleotides can also induce vesicle formation,and compared with deoxyribo-oligonucleotides,ribo-oligonucleotides exhibit a higher inductive efficiency.
Recently,we reported that deoxyribo-oligonucleotides could induce single chained cationic surfactant aggregation to form vesicles.In this paper,we will present that ribo-oligonucleotides can also induce vesicle formation,and compared with deoxyribo-oligonucleotides,ribo-oligonucleotides exhibit a higher inductive efficiency.
2013, 24(01): 85-88
Abstract:
The reaction between urea and formaldehyde in water solution was theoretically investigated by using B3LYP and MP2 methods.It was found that the addition of the nitrogen atom in urea to the carbonyl group in formaldehyde precedes the proton transfer and the proton migration from water to the carbonyl group occurs before the proton abstraction from the nitrogen.With one or two water molecules involved in the TS,the activation energy barrier is lowered compared to the TS of the mechanism with no water participation.The energy change along the reaction coordinate clearly shows that a zwitterionic-like intermediate does not exist on the PES.The reaction between urea and formaldehyde occurs in a concerted mechanism but with asynchronous characters.This is different from the stepwise mechanism recently found for the amination reactions of formaldehyde.
The reaction between urea and formaldehyde in water solution was theoretically investigated by using B3LYP and MP2 methods.It was found that the addition of the nitrogen atom in urea to the carbonyl group in formaldehyde precedes the proton transfer and the proton migration from water to the carbonyl group occurs before the proton abstraction from the nitrogen.With one or two water molecules involved in the TS,the activation energy barrier is lowered compared to the TS of the mechanism with no water participation.The energy change along the reaction coordinate clearly shows that a zwitterionic-like intermediate does not exist on the PES.The reaction between urea and formaldehyde occurs in a concerted mechanism but with asynchronous characters.This is different from the stepwise mechanism recently found for the amination reactions of formaldehyde.
