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991.
992.
The reaction 48Ti(t, d)49Ti leading to the ground and first excited states of 49Ti has been studied at triton energies of 2.75 and 3.0 MeV. The cross section to the ground state of 49Ti has been analysed using the DWBA with a previously determined bound-state well geometry to obtain a value for the (t, d) normalization factor of D2 = (3.29 ± 0.40) × 104 MeV2 · fm3. This value is in agreement with that obtained from a comparison of the (d, t) reaction with heavy-ion single-neutron transfer reactions. Using this value of the normalization factor the rms radius of the component in the first excited state of 49Ti is found to be 4.42 ± 0.07 fm (point neutron), corresponding to the use of a local bound-state potential well. 相似文献
993.
The results of X-ray crystallographic studies of the molecular structure of mesitil are presented. The two carbonyl planes make an angle of 177.77° whereas the mesityl groups are forced out of the carbonyl planes by 75.82° and 78.02°. 相似文献
994.
Lian‐Dong Guo Xiong‐Zhi Huang Shi‐Peng Luo Wen‐Sen Cao Prof. Yuan‐Ping Ruan Dr. Jian‐Liang Ye Prof. Dr. Pei‐Qiang Huang 《Angewandte Chemie (International ed. in English)》2016,55(12):4064-4068
The first total synthesis of the alkaloid (?)‐haliclonin A is reported. The asymmetric synthesis relied on a novel organocatalytic asymmetric conjugate addition of nitromethane with 3‐alkenyl cyclohex‐2‐enone to set the stereochemistry of the all‐carbon quaternary stereogenic center. The synthesis also features a Pd‐promoted cyclization to form the 3‐azabicyclo[3,3,1]nonane core, a SmI2‐mediated intermolecular reductive coupling of enone with aldehyde to form the requisite secondary chiral alcohol, ring‐closing alkene and alkyne metathesis reactions to build the two aza‐macrocyclic ring systems, and an unprecedented direct transformation of enol into enone. 相似文献
995.
Wu Y Jin L Xue Y Xie DQ Kim CK Guo Y Yan GS 《Journal of computational chemistry》2008,29(8):1222-1232
The hydrolysis reaction of N,N-dimethyl-N'-(2-oxo-1, 2-dihydro-pyrimidinyl)formamidine (DMPFA), a model compound of the antivirus drug amidine-3TC (3TC = 2', 3'-dideoxy-3'-thiacytidine), is investigated by the hybrid density functional theory B3LYP/6-31+G (d,p) method. The hydrolysis reaction of the title compound is predicted to undergo via two pathways, each of which is a stepwise process. Path A is the addition of H2O to the C=N double bond in the amidine group to form a tetrahedral structure in its first step, and then the transfer of the H atom of hydroxyl leads to the corresponding products via four possible channels. Path B simultaneously involves the nucleophilic attack of H2O to the C atom of the C=N bond and the proton transfer to the N atom of amino group leading to the cleavage of the C-N single bond in the amidine group. The results indicate that path A is more favorable than path B in the gas phase. Moreover, to simulate the title reaction in aqueous solution, water-assisted mechanism and the cluster-continuum model, based on the SCRF/CPCM model, are taken into account in our work. The results indicate that it is rational for two water molecules served as a bridge to assist in the first step of path A and that cytosine rather than the cytosine-substituted formamide should be released from the tetrahedral intermediate via s six-membered cycle transition state (channel 2). Our calculations exhibit that the process toward the tetrahedral intermediate is the rate-determining step both in the gas phase and in aqueous solution. 相似文献
996.
Pratik K. Sen Nasimul Gani Jayanta K. Midya Biswajit Pal 《Transition Metal Chemistry》2008,33(2):229-236
The kinetics of reduction of tetrachloroaurate(III) by glycine has been spectrophotometrically studied in NaOAc–AcOH buffer
in the pH range 3.73–4.77. The reaction is first order with respect to both Au(III) and glycine. Both H+ and Cl− ions have inhibiting effects on the reaction rate. The rate decreases with a decrease in the dielectric constant of the medium.
AuCl4− and AuCl3(OH)− are presumed to be the predominant oxidizing species under the conditions of the experiment. The reaction of gold(III) and
zwitterionic species of glycine proceeds with the intermediate formation of gold(I) and iminic cation and the latter subsequently
hydrolyses in a fast step to produce formaldehyde and ammonium ion. Formaldehyde was identified as the only organic product
by 1H NMR spectroscopy. 相似文献
997.
Goldsmith RH Vura-Weis J Scott AM Borkar S Sen A Ratner MA Wasielewski MR 《Journal of the American Chemical Society》2008,130(24):7659-7669
A 4-(pyrrolidin-1-yl)phenyl electron donor and 10-cyanoanthracen-9-yl electron acceptor are attached via alkyne linkages to the bridgehead carbon atoms of bicyclo[2.2.2]octane and all three benzo-annulated bicyclo[2.2.2]octanes. The sigma-system of bicyclo[2.2.2]octane provides a scaffold having nearly constant bridge geometry on which to append multiple, weakly interacting benzo pi-bridges, so that the effect of incrementally increasing numbers of pi-bridges on electron transfer rates can be studied. Surprisingly, photoinduced charge transfer rates measured by transient absorption spectroscopy in toluene show no benefit from increasing the number of bridge pi-systems, suggesting dominant transport through the sigma-system. Even more surprisingly, the significant changes in hybridization undergone by the sigma-system as a result of benzo-annulation also appear to have no effect on the charge transfer rates. Natural Bond Orbital analysis is applied to both sigma- and pi-communication pathways. The transient absorption spectra obtained in 2-methyltetrahydrofuran (MTHF) show small differences between the benzo-annulated molecules that are attributed to changes in solvation. All charge transfer rates increase significantly upon cooling the MTHF solutions to their glassy state. This behavior is rationalized using combined molecular dynamics/electronic structure trajectories. 相似文献
998.
A mass spectrometric method utilizing regioselective ion-molecule reactions has been developed for the differentiation of protonated isomeric aromatic diamines in FT-ICR, linear quadrupole ion trap and triple quadrupole mass spectrometers. 相似文献
999.
P. Aghamkar S. Duhan M. Singh N. Kishore P. K. Sen 《Journal of Sol-Gel Science and Technology》2008,46(1):17-22
A novel sorbent for the removal of heavy metals, hydroxyapatite/poly (vinyl alcohol) cryogel, was studied. The HAp/PVA cryogel
was characteristic of macroporous structure. The experiments for Cd2+ sorption by HAp/PVA cryogel were conducted at various operating conditions such as sonication, sorption time, Cd2+ concentration, temperature, pH, and HAp/PVA mass ratio. It was concluded that the sorption was considerably affected by sorption
time, Cd2+concentration, temperature and HAp/PVA mass ratio. Nevertheless, there was slight dependence of sorption on sonication and
pH. The influences of different parameters were discussed in detail in the paper. The main mechanism was suggested to be ion-exchange. 相似文献
1000.
An efficient and novel procedure for the preparation of pyrazolo[3,4-b]pyridine derivatives through multi-component reaction of aldehyde, 5-amino-3-methyl-1-phenylpyrazole and malononitrile or cyanoacetate in [bmim][BF4] is described in this paper. Advantages of the method presented here include mild conditions, high yields together with a green nature and ease of recovery and reuse of the reaction medium. 相似文献