bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNMR study of the azacrown ether conformations in solution
Authors: Dong‐Hui Wu , Lian‐Fang Shen , Guo‐Pin Xue , Cheng‐Tai Wu 
Published: April 2011

AbstractThe NMR methods (including 1H NMR, 13C NMR, variable temperature method and the novel ID EXSY technique) were employed to study the conformation of azacrown ethers 1—5 in solution. There are two classes of conformation in which the azacrown ethers exist in solution according to their molecular structure. Two kinds of intramolecular motion of the azacrown ethers were observed, one is the vibration of the macrocyclic ring and the other is its inversion. The ether rings which contain oxygens are more flexible than that constructed by nitrogens in the present case because of the tetrahedron structure of the nitrogen atoms and the hindrance of the groups Ts connected to the nitrogens. Some thermodynamical parameters of the ring inversion process were obtained.
Tetrahydrofolate coenzyme models: I. Synthesis of 1‐methyl‐2‐phenyl‐3‐aryl imidazolinium iodide and benzylidyne (phenyl‐substituted one carbon unit) transfer reactions
Authors: Chi‐Zhong Xia , Pei‐Wen Zhou , Jing‐Fan Ding 
Published: April 2011

AbstractFour 1, 2, 3‐trisubstituted imidazolinium iodides which were used as 5,10 ‐+CPh‐THF model (7—10) at formic acid oxidation level were synthesized. The benzylidyne group (phenyl‐substituted one carbon unit) transfer reactions from these compounds to Grignard reagent were investigated, and the reactions of these compounds with KBH4 and NaOH were also studied.
Microenvironmental control of photochemical reactions: II. Fluorescence quenching of naphthalene and 1,3‐di‐(α‐naphthyl)propane by RNA and bases in aqueous methanol
Authors: Xue‐Gong Lei , Rui‐Qiang Xie , You‐Cheng Liu 
Published: April 2011

AbstractThe fluorescence quenching of naphthalene (2) and 1,3‐di(α‐naphythyl)propane (1) by RNA and bases in methanol‐water (v:v = 1:1) binary solvents in the presence or absence of cyclodextrin (CD) has been investigated. The results show that both the monomer and excimer fluorescence of 1 can be quenched by these quenchers. The quenching and rates depend on the quencher and temperature. It is shown that there is a critical temperature (Tc) for each quencher. Below Tc, the excimer fluorescence spectra show vibrational structures and the Stern‐Volmer plots are straight lines (for uracil and cytosine); while above the Tc, the vibrational structures disappear and the Stern‐Volmer plots deviate from linearity and curve upward. The former is a static process; while the latter is a mixture of both static and dynamic processes. The addition of α‐CD has no effect on the fine structure; whereas β‐CD prevents the appearance of this structure efficiently. The quenching rates both for the monomer and excimer of 1 by bases except cytosine in the presence of β‐CD at ambient temperature are not changed; the quenching of fluorescence of 1 by RNA in the presence of β‐CD, however, is hindered. Time‐resolved fluorescence study shows that the excimer fine structures appear from the zero time. The intensity of fine structures depend on the fraction of water (π) in binary solvents, and it is independent of the pH value of the solvents. It is suggested that bases and RNA induced aggregates (perhaps microcrystal) are formed, in which the motion of molecules 1 is limited.
Studies on sulfinatodehalogenation: XVI. Sodium dithionite‐initiated addition of perfluoroalkyl iodides to terminal alkynes
Authors: Wei‐Yuan Huang , Long LÜ , Yuan‐Fa Zhang 
Published: April 2011

AbstractReaction of perfluoroalkyl iodides with a series of alkynes under sulfinatodehalogenation condition gave a mixture of E/Z adducts very readily in high yield, thus constituted a mild, convenient and effective new method for the addition of perfluoroalkyl iodides to alkynes. Under the same condition, in the presence of 1‐hexyne perfluoroalkyl bromide and 1,1,1‐trichlorotrifluoroethane reacted only to give sulfinates as the major products. A radical mechanism was proposed for the addition reaction.
Rongalite‐initiated addition of perfluoroalkyl iodides to olefins
Authors: Bing‐Nan Huang , Jin‐Tao Liu 
Published: April 2011

AbstractPerfluoroalkyl iodides reacted with olefins in aqueous acetonitrile in the presence of Rongalite‐sodium bicarbonate under mild conditions to give the corresponding 1:1 adducts in moderate to high yields. The formation of these products and the orientation of the addition seemed to show that radicals took part in the reaction. This provides a convenient method for perfluoroalkylation.
Aggregation of l,3‐di(α‐naphthyl)propane and di(α‐naphthylmethyl)ether in aqueous binary solvents
Authors: Xue‐Gong Lei , You‐Cheng Liu 
Published: April 2011

AbstractThe UV absorption and fluorescence spectra of 1,3‐di (α‐naphthyl) propane (1), di (α‐naphthylmethyl) ether (2), and α‐methylnaphthalene (3) in aqueous methanol, ethanol, and DMSO were recorded as a function of π value (fraction of water in binary solvents). The existence of two states, a metastable state (defined as m) and a stable stationary state (defined as s), of molecules 1 as well as 2 in the above cosolvents at high π was shown by the contrary fluorescence excimer to monomer intensity (Ie/Im) vs. π relationships of the samples prepared with different processes. On the basis of the π value, substrate concentration, and the temperature dependence of the UV spectra, fluorescence excitation and emission spectra, the chromophores of 1, 2 show the formation of aggregates in ground state at high π owing to the hydrophobic interaction. The m states consist of a supersaturated solution with aggregates, whereas the s states are suspended microcrystals or micro‐oil‐droplets with aggregates. The conformations of the molecules in the aggregates were discussed. Single crystal X‐ray structure of 2 is reported.
The crystal structure and conformation of 15‐phenyl‐bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one
Authors: Xiao‐Lan Wang , Jie‐You Xue , Zhong Hu , Shi‐Xiong Tang , Ru‐Ji Wang 
Published: April 2011

AbstractThe title compound has been synthesized and its crystal structure determined by X‐ray crystallographic method. The crystal is monoclinic, space group C2/c, with unit cell dimensions a=19.260 (3), b=11.217 (1), c=15.997 (1) Å; β=92.08 (2)° and Z=8.This is the first crystal structure determined in the series of bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one derivatives. The structure and the conformation of the cis‐cyclododecene moiety in this compound is demonstrated to be closely similar to the lowest energy conformer [lene 2333].
Theoretical studies on structure‐property relationships of cellulose and nitrocellulose: I. Conformation, stability and conductivity
Authors: He‐Ming Xiao , Jian‐Fen Fan , Yong‐Fu Li 
Published: April 2011

AbstractThe banding and electronic structures of a series of long‐chain macromolecules of cellulose, 2‐, 3‐, 6‐mononitrocellulose, 2,3‐,2,6‐, 3,6‐dinitrocellulose and trinitrocellulose as well as their structural units (i.e. single‐, double‐ or three‐ring systems) have been calculated by both the EH and CNDO/2 methods. The increase of molecular total energies is consistent with the decrease of their stabilities at the three conformations of gg, gt and tg. The Mulliken bond order of O—NO2 bond is the smallest in each molecule at any of the three conformations, which indicates that this bond is the weakest, and supports the view of initial homolytic cleavage of O—NO2 bond on slow thermal decomposition. The band gap at the edge of the first Brillouin zone far surpasses 5 eV for cellulose, and is less than 3 eV for mono‐, di‐, and trinitrocellulose. The results show that cellulose is a typical insulator, as we know, and it can be predicted that nitrocellulose has electric conductivity similar to that of semiconductor.
Theoretical studies on ammonia oxide and its unimolecular reactions
Authors: Yun‐Zhu Han , De‐Zhong Zhu , Cheng‐Da Zhao 
Published: April 2011

AbstractThe unimolecular reactions of ammonia oxide H3NO, isomerization and dehydrogenation, are investigated by ab initio MO calculations with the 4‐31G basis set. The geometries and energies of the reactant, transition states and products have been determined on the singlet potential energy surface. The reaction ergodography along the intrinsic reaction coordinate (IRC) for the two reactions have been performed. The vibrational frequency correlation diagram of the two reactions are analyzed along the IRC.
A study on hydrolytic polymerization of lanthanide ions
Authors: Qin‐Hui Luo , Meng‐Chang Shen , Xin‐Lu Bao , Yi Ding , An‐Bang Dai , An‐Pang Tai 
Published: April 2011

AbstractExperimental data of hydrolytic polymerization of lanthanide ions in aqueous solution were treated by graphic method, computer fitting and pq analysis, species present were ascertained and hydrolysis constants obtained. Ln (OH)2+ and Ln2 (OH)24+ predominated in the species of all hydrolysis products. When the first and the second hydrolysis constants were plotted against radii and effective nuclear charge of lanthanide ions, the curves obtained conformed with the “three‐division groups” rule. Correlation between hydrolysis constants of Ln2 (OH)24+ and other hydrolysis constants is linear.Using the above empirical correlations we calculated hydrolysis constants of all lanthanide ions and obtained satisfactory results which showed good regularity for hydrolysis of lanthanide ions and thus systematized all data of the reaction.
Conformational study of L‐lysine in aqueous solution by lanthanide shift probes
Authors: Ji‐Min Ren , Feng‐Kui Pei , Wen‐Yun Wang 
Published: April 2011

AbstractConformation of L‐lysine in aqueous solution was investigated by lanthanide shift probes (Dy, Ho, Er, Tm and Yb). Reilley's method was employed to separate the contact and dipolar components of the 13C paramagnetic shifts. This study reveals that Cα shift has the largest contact contribution while the other carbon shifts are dominated by the dipolar contribution. The average overall conformation of L‐lysine in aqueous solution is extended with the molecular backbone in trans form. In the complex, lanthanide ion coordinates to the carboxyl group with Ln—O bond length 2.2 Å and the whole ligand is located outside the zero‐dipolar shift cone of the lanthanide ion. The electronic spin density distribution on the ligand nuclei shows that the spin polarization is the predominant mechanism of the contact interaction for nuclei in close proximity to the bound lanthanide ion.
Photochemistry of endo and exo electronic configurations of biphenylyl methyl propanal
Authors: Guo‐Sheng Wu , He‐Qun Yin 
Published: April 2011

AbstractBoth direct and sensitized irradiations of the endo title compound lead to a decarbonylation product, 4‐isopropylbiphenyl, via Norrish Type 1 reaction, while the exo isomer gives a carbene intermediate and subsequently formaldehyde 2‐biphenylyl isopropyl hemiacetal, which in turn gradually decomposes to dimethyl phenylbenzyl alcohol at room temperature. The triplet pathway dominates the photoreaction of the exo isomer. The singlet and triplet lifetimes of the reactant are found to be 0.29 ns and 5.4 μs, respectively, 3(n, x*), 1(n, x*), 3(x, x*) electronic configurations of the exo isomer and 3(x, x*) of the endo isomer are photochemically active, but 1(x, x*) of the endo isomer shows indirect photoreactivity.
Palladium‐catalyzed cross‐coupling reaction of phenyl fluoroalkanesulfonates with organometallics
Authors: Qing‐Yun Chen , Ya‐Bo He 
Published: April 2011

AbstractThe palladium‐catalyzed cross‐coupling reaction of phenyl fluoroalkanesulfonates with organozinc, organotin and organoaluminum reagents in the presence of lithium chloride takes place to afford alkylbenzenes in good yields. However, the coupling reaction with organolithium and Grignard reagents proceeds unsatisfactorily with poor regioselectivity. On the basis of the isolation of an oxidative addition product of phenyl fluoroalkanesulfonate to palladium, a catalytic cycle in the reaction is suggested.
Synthesis and comparative study of reactivities of δ‐lactone, estor group and oxazinone ring in coumarin derivatives towards carbon or nitrogen nucleophiles
Authors: El‐Kafrawy  , Soliman  , Baker  , Mohamed  , El‐Kady  
Published: April 2011

AbstractCondensation of methyl 7‐methylcoumarin‐4‐acetate (2) with primary amines and with anthranilic acid gave 7‐methyl‐2‐oxo‐N‐aryl‐2H‐[1]‐benzopyran‐4‐acetamide (4a—d) and (7), respectively. Compound 7 underwent cyclization to give 2‐(7‐methyl‐2‐oxo‐2H‐[1]‐benzopyran‐4‐yl)‐methyl‐4H‐3,1‐benzoxazin‐4‐one (3). The reaction of 3 with aromatic amines gave the corresponding quinazolone derivatives 5 which tautomerises to the thermodynamically more stable isomer 6, whereas its reaction with Grignard reagents and aromatic aldehydes gave 8a, 8b, and 9a, 9b, respectively.
The synthesis of fluorine‐containing porphyrins
Authors: Wei‐Yuan Huang , Wu‐Ping Ma 
Published: April 2011

AbstractThe synthesis of polyfluoroalkoxyl substituted tetrakisphenylporphyrin is reported. The reaction is carrying out using Lewis acid BF3·OEt2 as catalyst and p‐chloranil as oxidant. The yields of the porphyrins are about 30–40%.
Investigation on the eigenvalue‐equation problem of molecular crystals and polymers
Authors: Yan Ji‐Min , Zhang Qi‐Yuan 
Published: April 2011

AbstractOne‐dimensional periodic system, such as molecular crystal and polymer, can be expressed as … ABABAB … structure, where A and B stand for a complete molecule or a part of a molecule. When (AB) is taken as a structure unit, one can obtain the complex generalized eigenvalue‐equation HAB (k) ‐ CAB (k) ‐ SAB (k) CAB (k) EAB (k); and if (BA) is taken as a structure unit, the corresponding eigenvalue‐equation is HBA (k) CBA (k) ‐ SBA (k) CBA (k) EBA (k). The relationship between the two equations has been investigated. The results of theoretical analysis are \documentclass{article}\pagestyle{empty}\begin{document}$ E_m^{{\rm BA}} (k) = E_m^{{\rm AB}} (k);\quad C_{j_{\rm a} m}^{{\rm BA}} (k) - C_{j_{\rm a} m}^{{\rm AB}} (k) \cdot \exp (i\Delta \phi) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ C_{j_{\rm b} m}^{{\rm BA}} (k)\quad C_{j_{\rm b} m}^{{\rm AB}} (k) \cdot \quad \exp [i(k.R_{ - 1} + \Delta \phi)] - C_{j_{\rm b} m}^{{\rm AB}} (k) \times \exp (i\Delta \phi) $\end{document} where ja and jb are the index number of atomic orbitals within (A) and (B) respectively, and m stands for the index number of crystal or polymer orbitals. This result has been verified by the concrete calculation of three periodic systems: (1) hydrogen‐molecular chain, …H (A) H (B) … H (A) H (B) …, (2) polyphenylene, … (A) (B) (A) (B) …, where (A) and (B) stand for =C (CH=)2 and ( HC)2 C= respectively, and (3) the TCNQ molecular column, … TCNQ (A). TCNQ (B) … TCNQ (A). TCNQ(B) … . The results can be generalized to two‐ and three‐dimensional systems straightforwardly.
A description of nitrogen‐nitrogen bond in terms of charge distributions
Authors: Cao Wei‐Liang , Marshall T. C. , Bader R. F.W. 
Published: April 2011

AbstractA theoretical analysis of properties of the shared interactions between two neighbouring nitrogen atoms in a variety of compounds is presented, based on properties of charge distributions derived from 6‐31 ++G** wave functions.Bond is characterized in terms of its bond order, bond ellipticity and the quantity of Laplacian of ρ at the bond critical point. The difference between the bond path angle and the corresponding geometrical angle provides a measure of the degree of relaxation for the charge density away from the geometrical constraints imposed by the nuclear framework. Comparisons have been made between the nitrogen‐containing compounds and isoelectronic hydrocarbons.Values of the NN bond energies, based on the properties of NN bond interatomic surface, are determined in three schemes.
A study of differential potentiometric stripping analysis for lead and cadmium with Nafion coated carbon fibre electrode
Authors: Dong Shao‐Jun , He Jun , Wang Yu‐Dong 
Published: April 2011

AbstractThe differential potentiometric stripping analysis (DPSA) with Nafion coated carbon fibre electrode has been studied, and a method to determine lead and cadmium in urine directly has been attempted. The effect of various experimental parameters on the DPSA response is discussed. The experimental conditions include 0.2M sodium perchlorate, deposition potential of −1.0 or −1.1 V and using 20 ppm mercuric ion as oxidizing agent. The response of the signal is in linear relation with the concentrations of lead and cadmium respectively up to 0.5 ppm. The electrode coated with Nafion film alleviates the interference from organics in urine samples.
1H and 13C NMR studies of lanthanide complex with 5‐sulfosalicylic acid
Authors: Ren Ji‐Min , Pei Feng‐Kui , Wang Wen‐Yun 
Published: April 2011

AbstractIn this paper, paramagnetic shifts have been measured for all 1H and 13C nuclei of 5‐sulfosalicylic acid (SSA) in the presence of the lanthanide ions in the second half of the series. The ligand forms isostructural complexes with these ions in aqueous solution. The separation of LISs was carried out by the use of the Reilley method and the calculated dipolar shifts were used to simulate the coordination structure of the complex. The result reveals that SSA is coordinated to lanthanide ion via two oxygens, one from the carboxylic group and the other from the phenolic group with Ln–O bond lengths equal to 2.47 Å. The lanthanide ion lies on the benzene plane and the carboxylic group is twisted 20° from the benzene ring. Of all the nuclei examined, those in the six‐membered chelate ring experience significant dipolar interactions and contact interactions. Small |G/A| ratios were obtained for two protons five bonds away from the central lanthanide ion, which shows that the number of bonds alone cannot be used as a criterion for neglecting contact shifts in aromatic ligand.
Structural studies on rare earth carboxylates: I. Studies on the crystal structure of tris(neopentanoato)‐tris(neopentanoic acid)neodymium(III) dimer, [NdA3(HA)3]2
Authors: Zhang De‐Long , Huang Chun‐Hui , Xu Guang‐Xian , Pan Zuo‐Hua 
Published: April 2011

AbstractThe title complex was synthesized and its structure was determined. The crystal is monoclinic with space group P21/n. Unit cell parameters are as follows: a=16.474(8), b=12.425(4), c=20.844(12)Å, β=109.27(4)°, Z=4. In each dimer, the two Nd atoms are connected through two pairs of bridging neopentanoate anions. The two carboxyl groups in each pair are in opposite position to Nd atom which are coplanar with them and the two planes are perpendicular with each other. In the complex each Nd atom is further coordinated with three neopentanoic acid molecules and one monodentate neopentanoate anion. The central atom is octa‐coordinated in a square‐antiprism arrangement.
Perfluoroalkylation of aromatic compounds with perfluoroalkyl radical generated from the oxidation of sodium perfluoroalkanesulfinate
Authors: Huang Wei‐Yuan , Xie Yuan 
Published: April 2011

AbstractSodium perfluoroalkanesulfinates [RfSO2Na(1), Rf = Cl (CF2)n; a, n = 4; b, n = 6; c, n = 8] on oxidation with various single electron oxidizing agents, such as Mn (OAc)3 · 2H2O and Ce (SO4)2, yielded perfluoroalkyl radicals capable of perfluoroalkylating aromatic compounds to give a mixture of o‐and p‐monoperfluoroalkylated products. Thus, this reaction provides a new method for the synthesis of o‐and p‐monoperfluoroalkyl substituted aromatic compounds.
Diastereoselective alkylation of the ( + )‐ketopinic acid ketimine derived from benzylamine
Authors: Deng Jin‐Gen , Hu Wen‐Hao , Liu Gui‐Lan , Mi Ai‐Qiao , Jiang Yao‐Zhong 
Published: April 2011

AbstractAlkylation of the ketimine 2 obtained from condensation of (+)‐ketopinic acid and benzylamine with a variety of alkylating agents gives the products whose trends in diastereomeric excesses (1 — 100% O.P.) appear to correlate with the structure and reactivity of electrophilic agents. Using excess n‐butyl lithium and allylic or benzylic halides, β‐alkylation occured.
Some reactions of 4‐aryl‐1 (2H)‐phthalazinones
Authors: Soliman A. Y. , Bakeer H. M. , Sayed M. A. , Islam I. , Mohamed A. A. 
Published: April 2011

AbstractThe behaviors of 4‐aryl‐1 (2H)‐phthalazinones (1a–c) toward carbon nucleophiles (Grignard reagents) and secondary amine under Mannich conditions as well as the nucleophilic substitution reaction on chlorophthalazine derivatives have been studied.
Studies on sulfinatodehalogenation: XVIII. The reaction of perfluoroalkyl iodides with α‐methylene cyclic ethers
Authors: Huang Wei‐Yuan , Zhang Han‐Zhong , Zhuang Jin‐Lian 
Published: April 2011

AbstractPerfluoroalkyl iodides reacted with various α‐methylene oxacycloalkanes in the presence of sodium dithionite to give ring opening adducts. The reaction provided an efficient method for the syntheses of polyfunctional organofluorine compounds.
Asymmetric carbonyl addition with the homochiral ketimine derived from (+) or (−)‐pinanone and benzylamine
Authors: Mi Ai‐Qiao , Chen Yuan‐Wei , Wang Jing , Yang Gui‐Shu , Jiang Yao‐Zhong 
Published: April 2011

AbstractThe carbonyl addition of the pinanone ketimine derived from (+) or (−)‐2‐hydroxy‐pinan‐3‐one and benzylamine has been studied and the optically active α,β‐substituted‐β‐aminoethanol derivatives were obtained in good chemical yields (36.5‐69.5%) with optical purity ranging from 1.4% to 99.9%.
Evidence for the Existence of a Specific G Protein‐Coupled Receptor Activated by Guanosine
Authors: Volpini Rosaria , Marucci Gabriella , Buccioni Michela , Dal Ben Diego , Lambertucci Catia , Lammi Carmen , Mishra Ram C. , Thomas Ajiroghene , Cristalli Gloria 
Published: April 2011

AbstractGuanosine, released extracellularly from neurons and glial cells, plays important roles in the central nervous system, including neuroprotection. The innovative DELFIA Eu‐GTP binding assay was optimized for characterization of the putative guanosine receptor binding site at rat brain membranes by using a series of novel and known guanosine derivatives. These nucleosides were prepared by modifying the purine and sugar moieties of guanosine at the 6‐ and 5′‐positions, respectively. Results of these experiments prove that guanosine, 6‐thioguanosine, and their derivatives activate a G protein‐coupled receptor that is different from the well‐characterized adenosine receptors.
Relative input strength rapidly regulates dendritic structure of chick auditory brainstem neurons
Authors: Sorensen Staci A. , Rubel Edwin W. 
Published: April 2011

AbstractCompetition between presynaptic inputs has been suggested to shape dendritic form. This hypothesis can be directly tested on bitufted, auditory neurons in chicken nucleus laminaris (NL). Each NL neuron contains two relatively symmetrical dendritic arbors; the dorsal dendrites receive excitatory glutamatergic input from the ipsilateral ear, and the ventral dendrites receive corresponding input from the contralateral ear. To assess the effect of relative synaptic strength on NL dendrites, we used single‐cell electroporation; electrophysiology; and live, two‐photon laser scanning microscopy to manipulate both the amount and the balance of synaptic input to the two matching sets of dendrites. With simultaneous activation, both sets of dendrites changed together, either growing or retracting over the imaging period. In contrast, stimulation of only one set of dendrites (either dorsal or ventral) resulted in the unstimulated dendrites losing total dendritic branch length, whereas the stimulated dendrites exhibited a tendency to grow. In this system, balanced input leads to balanced changes in the two sets of dendrites, but imbalanced input results in differential changes. Time‐lapse imaging revealed that NL dendrites respond to differential stimulation by first decreasing the size of their unstimulated dendrites and then increasing the size of their stimulated dendrites. This result suggests that the relative activity of presynaptic neurons dynamically controls dendritic structure in NL and that dendritic real estate can rapidly be shifted from inactive inputs to active inputs. J. Comp. Neurol. 519:2838–2851, 2011. © 2011 Wiley‐Liss, Inc.