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1.
Alexander Kaiser Klaus K. Mayer Andreas Sellmer Wolfgang Wiegrebe 《Monatshefte für Chemie / Chemical Monthly》2003,43(11):343-354
The molecular ion 1 of N-(n-propoxy)benzaldimine I rearranges by an 1,5-H-shift to the δ-distonic ion 2 which subsequently cyclizes to the α-distonic ion 3. Homolytic cleavage of the N–O bond in 3 results in the δ-distonic ion 4 which expels CH2O leading to the β-distonic ion 5. Ion 5 is also formed from the molecular ions of tetrahydrooxazines II and III and from M+• of phenylazetidine IVa. In a subsequent step, ion 5 cyclizes to the N-protonated 3,4-dihydroisoquinolinium ion 6. The syntheses of II–IV and their derivatives are described. 相似文献
2.
E. Yu. Fursova O. V. Kuznetsova V. I. Ovcharenko G. V. Romanenko A. S. Bogomyakov M. A. Kiskin I. L. Eremenko 《Russian Chemical Bulletin》2007,56(9):1805-1808
A method was developed for the synthesis of mixed-metal heterospin compounds with the direct coordination of the nitroxide
fragment based on the replacement of acetonitrile molecules in the heterotrinuclear complex [Co2Gd(NO3)Piv6(CH3CN)2] with nitroxide molecules. The molecular and crystal structure of the heterospin mixed-ligand heterotrinuclear CoII, GdIII, CoII complex [Co2Gd(NO3)Piv6(NIT-Me)2], where NIT-Me is stable nitronyl nitroxide, was established. The magnetic properties of this complex were investigated in
the temperature range of 2–300 K. The coordination of nitroxide groups to CoII ions is responsible for strong exchange interactions between the unpaired electrons in the exchange clusters {>-·O-CoII}, resulting in the virtually complete spin coupling between each coordinated >N-·O group and one of the unpaired electrons
of each CoII ion at temperatures below 200 K.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1742–1745, September, 2007. 相似文献
3.
Jiri Brus Hana Petříčková Jiri Dybal 《Monatshefte für Chemie / Chemical Monthly》2002,133(12):1587-1612
Summary. A brief overview of our recent results concerning the application of 2D CRAMPS experiments to investigate a wide range of
materials is presented. The abilities of the 2D 1H–1H spin-exchange technique to characterize the structure of organic solids as well as the limitations resulting from segmental
mobility and from undesired coherence transfer are discussed. Basic principles of 1H NMR line-narrowing and procedures for analysis of the spin-exchange process are introduced. We focused to the qualitative
and quantitative analysis of complex spin-exchange process leading to the determination of domain sizes and morphology in
heterogeneous multicomponent systems as well as the characterization of clustering of surface hydroxyl groups in polysiloxane
networks. Particular attention is devoted to the determination of the 1H–1H interatomic distances in the presence of local molecular motion. Finally we discuss limitations of the 13C–13C correlation mediated by 1H–1H spin exchange to obtain structural constraints. The application of Lee-Goldburg cross-polarization to suppress undesired coherence transfer is proposed.
Corresponding author. E-mail: brus@imc.cas.cz
Received May 28, 2002; accepted (revised) July 1, 2002 相似文献
4.
Lianming Zhao Wenyue Guo Zhaochun Liu Yuanyuan Li Xiaoqing Lu 《Theoretical chemistry accounts》2011,128(3):349-358
We report herein a comprehensive study of the gas-phase Fe+-mediated oxidation of ethane by N2O on both the sextet and quartet potential energy surfaces (PESs) using density functional theory. The geometries and energies
of all the relevant stationary points are located. Initial oxygen-atom transfer from N2O to iron yields FeO+. Then, ethane oxidation by the nascent oxide involves C–H activation forming the key intermediate of (C2H5)Fe+(OH), which can either undergo C–O coupling to Fe+ + ethanol or experience β-H shift giving the energetically favorable product of FeC2H4
+ + H2O. Reaction of FeC2H4
+ with another N2O constitutes the third step of the oxidation. N2O coordinates to FeC2H4
+ and gets activated by the metal ion to yield (C2H4)Fe+O(N2). After releasing N2 through the direct H abstraction and/or cyclization pathways, the system would be oxidized to ethenol, acetaldehyde, and
oxirane, regenerating Fe+. Oxidation to acetaldehyde along the cyclization –C–to–C hydrogen shift pathway is the most energetically favored channel. 相似文献
5.
A novel polymer-forming diimide–diacid, 5,5′-bis[4-(4-trimellitimido phenoxy)phenyl]-hexahydro-4,7-methanoindan (II), was prepared by the condensation reaction of 5,5′-bis[4-(4-aminophenoxy)phenyl]-hexahydro-4,7-methanoindan with trimellitic
anhydride. A series of novel aromatic poly(amide–imide)s (PAIs) containing polycyclic cardo groups was prepared by the direct
polycondensation of II with various aromatic diamines using phosphorylation techniques. The polymers had inherent viscosities between 0.71 and 0.96 dl/g.
The polymers were soluble in polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide, and could be cast from their DMAc solutions into transparent, flexible, and tough films, except for III
a
. These films had yield strengths of 85–114 MPa, tensile strengths of 77–102 MPa, an elongation at break of 8–17%, and initial
moduli of 2.0–2.7 GPa. Wide-angle X-ray diffraction revealed that the polymers are amorphous. The glass-transition temperatures
of the polymers were in the range 242–312 °C. All the PAIs exhibited no appreciable decomposition below 430 °C, and their
10%-weight-loss temperatures were in the range 484–507 °C in nitrogen and 494–515 °C in air.
Received: 26 January 1999 Accepted in revised form: 11 May 1999 相似文献
6.
Gregor Radau 《Monatshefte für Chemie / Chemical Monthly》2003,134(7):1033-1036
Summary. The syntheses of dipeptide esters containing a C-terminal L-proline moiety using carbodiimides as coupling reagents strongly depend on the choice of appropriate conditions. Thus, the
use of DCC prefers the formation of the undesirable N,N′-dicyclohexylurea derivative 3 as a consequence of a CO → N-shift in the O-acyl isourea intermediate instead of the desired dipeptide ester 4. In our hands, only DIC was able to yield the desired product exclusively.
E-mail: radau@pharmazie.uni-greifswald.de
Received November 7, 2002; accepted December 4, 2002
Published online May 6, 2003 相似文献
7.
E. K. Beloglazkina A. G. Majouga A. A. Moiseeva M. G. Tsepkov N. V. Zyk 《Russian Chemical Bulletin》2007,56(2):351-355
The reaction of 5-[2-(methylthio)ethyl]-3-phenyl-2-thioxoimidazolidin-4-one (LH) with salts MCl2· xH2O (M = Co, Ni, Cu; x = 2, 6) afforded the [M(L)Cl]n complexes of NiII, CoII, and CuII. The electrochemical behavior of the LH ligand and its complexes was studied using the cyclic voltammetry and rotating disk
electrode techniques. The structures of the synthesized compounds were determined by the data of UV—Vis and IR spectroscopy,
mass spectrometry, and electrochemical characteristics.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–343, February, 2007. 相似文献
8.
Mohamed El-Sayed Hardy Müller Gerd Rheinwald Heinrich Lang Stefan Spange 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):361-370
Summary. N-(2′-Hydroxy-4′-N,N-dimethylaminobenzylidene)-4-nitroaniline [HDBN] has been used as a model for investigating intra- and intermolecular D–A (donor–acceptor) interactions in various environments
by means of UV/Vis spectroscopy. UV/Vis spectra of HDBN have been measured in various solvents, ethanolic solutions of different pH, adsorbed on silica, and in the solid state. A bathochromic shift of νmax is observed with increasing the dipolarity/polarizability and HBD (hydrogen bond donor) capacity of the solvent, which is
described by means of a multiple LSE (linear solvation energy) relationship in terms of the empirical Kamlet-Taft solvent polarity parameters. The adsorption of HDBN on Aerosil? 300-silica particles in non-HBA (hydrogen bond acceptor) solvents is explained in the same sense. Mobile protons and sol–gel
entrapping cause a hypsochromic shift due to protonation of the lone electron pair of the 4′-N,N-dimethylamino group. Hydroxide ions attack the 2′-hydroxy group which causes a bathochromic shift. A strong intramolecular
hydrogen bond between the 2′-hydroxyl hydrogen and the imine nitrogen atom is present in the solid-state structure causing
an unprecedented bathochromic shift.
Corresponding author. E-mail: stefan.spange@chemie.tu-chemnitz.de
Received July 8, 2002; accepted (revised) September 30, 2002 相似文献
9.
Molecular geometry, crystal packing and thermal stability of trans-1,4-cyclohexanedicarboxylic acid, 1,4-dibromo (I) are examined, in order to analyse the relative influence of the different intermolecular interactions at play. From a comparison
with the corresponding properties of trans1,4-cyclohexanedicarboxylic acid (II), some insights on the results of the competition between Br and carboxylic groups are obtained. In the crystalline state,
the molecules of both compounds present chair centrosymmetric geometry and build infinite chains through ring hydrogen bonds
involving the carboxylic groups. These groups are axial in I and equatorial in II, giving rise to different assembly of the chains. In both compounds there is in general good agreement between the in-crystal
geometry and the B3LYP/LanL2DZ optimized geometry of the corresponding isolated molecule. The only significant differences
are related to the carboxylic groups. The intermolecular contacts in I have been rationalized on the basis of a graph set analysis. A molecular dynamics based method has been used to analyse the
temperature dependence of the mean life time of the different kinds of hydrogen bonds characterized in I. It has been found that the O–H⋅ < eqid2 > ⋅O and C–H⋅ < eqid3 > ⋅O(carbonyl) interactions are the main source of thermal stability. The melting point of I determined within this approach agrees very well with the experimental value. 相似文献
10.
Erik Rakovský Ľudmila Žúrková Jaromír Marek 《Monatshefte für Chemie / Chemical Monthly》2002,133(3):277-283
Summary. Anhydrous 1,6-hexanediammonium dihydrogendecavanadate ((HdaH2)2H2V10O28, 1) was prepared by reaction of V2O5 with 1,6-hexanediamine in aqueous solution. The crystal structure of 1 was determined, and the proton positions in the H2V10O28
4− anion were calculated by the bond length/bond number method. The protons are bound to the centrosymmetrically oriented μ–OV3 groups of the decavanadate anion. Based on the analysis of IR spectra of 1 prepared from H2O and D2O, the absorption band at 871 cm−1 can be attributed to δ(V–Ob–H) vibrations.
Received August 3, 2001. Accepted (revised) October 8, 2001 相似文献
11.
V. N. Emel’yanenko S. P. Verevkin E. N. Burakova G. N. Roganov M. K. Georgieva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(8):1271-1279
The enthalpies of formation of δ-hexanolactone and δ-nonanolactone were determined by combustion calorimetry. Conformational
analysis and quantum-chemical calculations of equilibrium structures, fundamental vibrations, moments of inertia, and total
energies were performed for δ-pentanolactone (I), δ-hexanolactone (II), and δ-nonanolactone (III) by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and G3MP2 methods. The experimental IR spectra and calculated vibrational frequencies were used to suggest the assignment
of vibrational frequencies of stable conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. A thermodynamic analysis of mutual isomerization
in the gas and liquid phases over the temperature range 298.15–900 K and liquid-phase polymerization of γ- and δ-pentanolactones
and 4-pentenoic acid over the temperature range 298.15–500 K was performed. 相似文献
12.
E. V. Starodubtseva O. V. Turova M. G. Vinogradov L. S. Gorshkova V. A. Ferapontov 《Russian Chemical Bulletin》2005,54(10):2374-2378
The rate of hydrogenation of γ-ketoesters MeCOCH2CH2COOR (R = Et, Pri, But) in the presence of the chiral RuII—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents
of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially
formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)2—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester
(R = Et) in EtOH is attained in 5 h at 60 °C under an H2 pressure of 60–70 atm.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2301–2304, October, 2005. 相似文献
13.
Guillaume Laconde Pascal Carato Jacques H. Poupaert Pascal Berthelot Patrick Depreux Jean-Pierre Hénichart 《Monatshefte für Chemie / Chemical Monthly》2003,134(7):1037-1043
Summary. This paper reports an one-pot method for the concomitant alkylation – oxidation (aromatization) of indolines, particularly
effective to get easy access to N-alkyl-6-nitroindoles, which are useful platforms in medicinal chemistry. N-alkyl-6-nitroindoles are obtained in good yield (64–91%) by reaction at room temperature in non-degassed DMF of 6-nitroindoline, an alkyl halide, and NaH as base. The presence of NaH appears to be essential for a high yield conversion.
Corresponding author. E-mail: pdepreux@phare.univ-lille2.fr
Received December 3, 2002; accepted December 9, 2002
Published online May 26, 2003 相似文献
14.
Rahman Hosseinzadeh Ali Sharifi Kourosh Tabar-Heydar Farshid Mohsenzadeh 《Monatshefte für Chemie / Chemical Monthly》2002,133(11):1413-1415
Summary. N,N-Dimethylhydrazones of ketones and aldehydes undergo facile cleavage to the corresponding carbonyl compounds upon exposure
to microwaves in water containing a catalytic amount of PdCl2–SnCl2 in high yields.
Corresponding authors. E-mail: rahman@umz.ac.ir
Received December 27, 2001. Accepted (revised) February 6, 2002 相似文献
15.
Martin Emsenhuber Peter Pöchlauer Jean-Marie Aubry Véronique Nardello Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2003,134(3):387-391
Summary. Evidence for novel chemical sources of singlet oxygen based on the conversion of ozone by tin(II) in acetic acid or nitrite
ions in water was found by screening a selection of inorganic salts by means of a sensitive detector for exothermic processes
(SEDEX) and a N2-cooled Ge-diode for singlet oxygen luminescence measurements.
Corresponding author. E-mail: heinz.falk@jku.at
Received July 18, 2002; accepted August 23, 2002 相似文献
16.
Klaus Burger Jan Spengler Lothar Hennig Rainer Herzschuh Samy A. Essawy 《Monatshefte für Chemie / Chemical Monthly》2000,131(5):463-473
Summary. Homochiral Nα-methyl-2,3-diaminopropionic and Nα-methyl-2,4-diaminobutyric acid derivatives 8a,b were obtained via a stereoconservative four-step synthesis starting from hexafluoroacetone protected L-aspartic and L-glutamic acid 2a,b, respectively. Hexafluoroacetone protected ω-isocyanato-α-methylamino acids 4a,b– the key intermediates of the synthesis – are versatile building blocks for amino acid and peptide modification and promising
candidates for combinatorial chemistry. Upon reaction with alcohols, compounds 4 give activated N
ω-urethane protected ω-amino-α-methylamino acid derivatives 5–7; upon reaction with amines, ω-ureido-α-methylamino acid derivatives 10–12 and 3-methylamino-pyrrolidin-2-ones 13 are available.
Received November 17, 1999. Accepted November 26, 1999 相似文献
17.
The IR and electronic absorption spectra of molten mixtures in the NaCl-CsCl-NaF-CoCl2, NaCl-KCl-NaF-CoCl2, and NaCl-KCl-NaKCO3-CoCl2 systems have been studied. The spectral data show that, for all molten mixtures, the composition ranges exist in which chloro
fluoro Co(Cl
n
F
m
)(n + m = 4–6) and carbonato chloro CoCl(CO3)4 − n
(n = 1–3) complex groups are formed at δ1 < δ1* and δ2 < δ2* (δ1* = F/Co and δ2* = CO3/Co). At δ1 ≥ δ1* and δ2 ≥ δ2*, the mixtures contain complexes homoligand Co and CoF64− and Co(CO3)46−. 相似文献
18.
Erik Rakovsky ?udmila ?úrková Jaromír Marek 《Monatshefte für Chemie / Chemical Monthly》2002,22(2):277-283
Anhydrous 1,6-hexanediammonium dihydrogendecavanadate ((HdaH2)2H2V10O28, 1) was prepared by reaction of V2O5 with 1,6-hexanediamine in aqueous solution. The crystal structure of 1 was determined, and the proton positions in the H2V10O28 4− anion were calculated by the bond length/bond number method. The protons are bound to the centrosymmetrically oriented μ–OV3 groups of the decavanadate anion. Based on the analysis of IR spectra of 1 prepared from H2O and D2O, the absorption band at 871 cm−1 can be attributed to δ(V–Ob–H) vibrations. 相似文献
19.
The reaction of N-benzoylphosphoramidic dichloride with amines afforded some new N-benzoylphos-phoric triamides with formula C6H5C(O)NHP(O)(X)2, X=NH–CH(CH3)2 (1), NH–CH2–CH(CH3)2 (2), NH–CH2–CH(OCH3)2 (3), N(CH3)[CH2CH(OCH3)2] (4) and N(CH3)(C6H11) (5) that were characterized by 1H,13C,31P NMR, IR spectroscopy and elemental analysis. The structures have been determined for compounds 4 and 5 by X-ray crystallography. These compounds contain one amidic hydrogen atom and form centrosymmetric dimmers via intermolecular
–P–O⋯H–N–hydrogen bonds besides weak C–H⋯O hydrogen bonds that lead to three-dimensional polymeric clusters in the crystalline
lattice. 相似文献
20.
H. Lawrence Clever 《Monatshefte für Chemie / Chemical Monthly》2003,134(5):745-750
Summary. There are more than 150 papers that report on the solubility of the four chloromethanes in water. Volume 62 of the Solubility
Data Series compiles and evaluates the papers concerned with the liquid–liquid solubility of the chloromethanes with water.
A similar evaluation has not been carried out for the vapor–liquid solubility at a partial pressure up to the saturation vapor
pressure of the four chloromethanes. This paper uses the liquid–liquid evaluated solubility values to calculate vapor–liquid
Henry’s constants. They are compared with a compilation of Henry’s constants with good agreements between the calculated constants and the median of the compiled constants. It is believed
that the calculated constants are a reliable set of values to use for the vapor–liquid solubility of the chloromethanes in
water.
E-mail: hlclever@worldnet.att.net
Received October 11, 2002; accepted October 22, 2002
Published online April 24, 2003
RID="a"
ID="a" Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70th birthday 相似文献