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101.
The racemic sesquiterpene isocomene ( 1 ) has been synthesized starting from 1,7-octadien-3-one ( 2 ) in a stereoselective manner (Scheme 2). In the key step 4 → 5 the C(7), C(8)-bond was formed by an intramolecular thermal ene reaction. Further elaboration of 5 involved the ring contraction 6 → 7 , the elimination 8 → 9 and the final olefin isomerization 9 → 1 . 相似文献
102.
Reactions of Iron Trichloride with Trithyazyl Chloride. Crystal Structure of [S4N4Cl]+[FeCl4]? Iron trichloride reacts with (NSCl)3 yielding S4N4[FeCl4]2, S3N3Cl2[FeCl4] or S4N4Cl[FeCl4], depending on the reaction conditions. The i.r. spectra prove the presence of [FeCl4]? ions for all three compounds. The 57Fe-Mössbauer spectra show a slight quadrupole splitting at 80 K for S3N3Cl2[FeCl4] (ΔEQ = 0.42 mm · s?1) and S4N4Cl[FeCl4] (ΔEQ = 0.23 mm · s?1), which indicates a slight deformation of the FeCl4? tetrahedra. The crystal structure of S4N4Cl[FeCl4] was determined and refined with X-ray diffraction data (2549 independent reflexions, R = 0.026). S4N4Cl[FeCl4] crystallizes in the triclinic space group P1 with two formula units per unit cell. The lattice constants are a = 712, b = 911, c = 1006 pm, α = 76.5°, β = 83.8° and γ = 80.5°. The structure consists of the so far unknown [S4N4Cl]⊕ cations and slightly deformed FeCl4? ions. The [S4N4Cl]⊕ ion consists of a S4N4 ring built up of two nearly planar S3N2 fragments having a dihedral angle of 136°. The average SN bond length is 157 pm, the SCI bond length 214 pm. 相似文献
103.
Prof. Dr. Maximilian Pöhm Harald Kolassa Kurt Jentzsch 《Monatshefte für Chemie / Chemical Monthly》1977,108(2):393-395
It is well known that in the ergot alkaloids of the peptide type the proline appears in thel-configuration. Different methods of acid hydrolysis may lead to various cleavage products; hydrolysis by HCl yieldsd-proline, on the other hand hydrolytic cleavage by means of strongly acid cation exchange resin preserved the orginall-configuration.
Teilveröffentlichung der Dissertation vonH. Kolassa, Univ. Wien, 1973. 相似文献
Teilveröffentlichung der Dissertation vonH. Kolassa, Univ. Wien, 1973. 相似文献
104.
Zusammenfassung Acenaphthylen wurde durch Anpolymerisation und zweifache Hochvakuumsublimation gereinigt. Die Reinigungsmethode wird ausführlich beschrieben.Bei verschiedenen Temperaturen wurde mit einer dilatometrischen Methode die thermische Bruttogeschwindigkeit gemessen. Zwischen 95 und 105 °C giltk
br=7,08·1010 exp (– 30,9 kcal/RT).Die beträchtliche Aktivierungsenergie der Bruttoreaktion ist sowohl auf eine große Aktivierungsenergie der thermischen Startreaktion als auch auf eine relativ hohe Wachstumsaktivierungsenergie zurückzuführen.Das Polymerisationsverhalten von Acenaphthylen kann vermutlich aufgrund seiner sterischen Eigenschaften erklärt werden.
Summary Acenaphthylene was purified by partial polymerisation, followed by double stage high vacuum sublimation. The method of purification is described in detail.The thermal overall rate was measured at different temperatures by a dilatometric method. Between 95 and 105 °C the following relation holds:k th=7,08 · 1010 exp (– 30,9 kcal/RT).The considerable energy of activation of the overall reaction depends on a relatively high energy of activation of both the thermal initiation and the propagation reaction.It is supposed, that the polymerisation behaviour of acenaphthylene depends mainly on its steric properties.相似文献
105.
The structure of p,p'-dibenzene (PDB) has been investigated by full geometry optimizations using the empirical force field (EFF) and MINDO/3 methods. While other structural parameters are in good agreement, the central bond length calculated by MINDO/3 (1.595 Å), as confirmed by an ab initio (STO-3G basis set) optimization (1.596 Å), is in striking contrast to the corresponding length calculated by EFF (1.543 Å). A detailed analysis of the electronic structure of PDB based on a quantitative perturbational molecular orbital treatment reveals that through-bond coupling of the four π systems is responsible for an elongation of the σ bond which mediates this interaction. Further studies using the EFF and MINDO/3 approaches demonstrate that extended C-C single bonds can arise even in structures with fewer than four π systems. The effect of substituents on the central bond length in PDB has been briefly investigated. (MINDO/3). A variety of other structures have been identified in which bond lengthening may result from through-bond coupling. 相似文献
106.
(±)-α-Acoradiene (4) has been synthesized from 3-methoxy-2-cyclohexenone by a sequence of 8 steps. The key steps (Scheme 6) are the regio- and stereoselective photo[2+2]addition 7→6 and the reductive fragmentation 6→5 . 相似文献
107.
The kinetics of the formation of the photochromic forms B and C of tetramethyl-dianthrone has been studied in triacetin and methylcyclohexane/2-methylpentane at several temperatures. A flash spectroscopy method was developed, which allows the recording of the transient behaviour of the sample as function of both – wavelength and time – using a single photoflash for excitation. The results show that the photochromic forms B and C are directly populated from the excited singlet state. In addition a new triplet-triplet absorption band in the near infrared region was detected. 相似文献
108.
Kurt Dietliker Paul Gilgen Heinz Heimgartner Hans Schmid 《Helvetica chimica acta》1976,59(6):2074-2099
Photochemistry of 4-substituted 5-Methyl-3-phenyl-isoxazoles. 4-Trideuterioacetyl-5-methyl-3-phenyl-isoxazole ([CD3CO]- 27 ), upon irradiation with 254 nm light, was converted into a 1:1 mixture of oxazoles [CD3CO]- 35 and [CD3]- 35 (Scheme 13). This isomerization is accompagnied by a slower transformation of ([CD3CO]- 27 ) into [CD3]- 27 . Irradiation of the isoxazole derivatives 28, 29, 30 and (E)- 31 yielded only oxazoles 36, 37, 38 and (E), (Z)- 39 ; no 4-acetyl-5-alkoxy-2-phenyl-oxazole, 2-acetyl-3-methyl-5-phenyl-pyrrole or 2-acetyl-4-methoxycarbonyl-3-methyl-5-phenyl-pyrrole, respectively, were formed (Scheme 9 and 10). Similarly (E)- 32 gave a mixture of (E), (Z)- 40 only (Scheme 11). Upon shorter irradiation, the intermediate 2H-azirines (E), (Z)- 41 could be isolated (Scheme 11). Photochemical (E)/(Z)-isomerization of the 2-(trifluoro-ethoxycarbonyl)-1-methyl-vinyl side chain in all the compounds 32, 40 and 41 is fast. At 230° the isoxazoles (E)- and (Z)- 32 are converted into oxazoles (E), (Z)- 40 . The same compounds are also obtained by thermal isomerization of the 2H-azirines (E), (Z)- 41 . The most probable mechanism for the photochemical transformations of the isoxazoles, as exemplified in the case of the isoxazole 27 , is shown in Scheme 13. A benzonitrile-methylide intermediate is postulated for the photochemical conversion of the 2H-azirines into oxazoles. 2H-Azirines are also intermediates in the thermal isoxazole-oxazole rearrangement. It is however not yet clear, if the thermal 2H-azirine-oxazole transformation involves the same transient species as the photochemical reaction. A mechanism for the photochemical isomerization of the 2H-azirine 11 to the oxazole 15 is proposed (Scheme 3). 相似文献
109.
The recently developed perturbed-chain statistical-associating-fluid theory (PC-SAFT) is investigated for a wide range of model parameters including the parameter m representing the chain length and the thermodynamic temperature T and pressure p. This approach is based upon the first-order thermodynamic perturbation theory for chain molecules developed by Wertheim [M. S. Wertheim, J. Stat. Phys. 35, 19 (1984); ibid. 42, 459 (1986)] and Chapman et al. [G. Jackson, W. G. Chapman, and K. E. Gubbins, Mol. Phys. 65, 1 (1988); W. G. Chapman, G. Jackson, and K. E. Gubbins, ibid. 65, 1057 (1988)] and includes dispersion interactions via the second-order perturbation theory of Barker and Henderson [J. A. Barker and D. Henderson, J. Chem. Phys. 47, 4714 (1967)]. We systematically study a hierarchy of models which are based on the PC-SAFT approach using analytical model calculations and Monte Carlo simulations. For one-component systems we find that the analytical model in contrast with the simulation results exhibits two phase-separation regions in addition to the common gas-liquid coexistence region: One phase separation occurs at high density and low temperature. The second demixing takes place at low density and high temperature where usually the ideal-gas phase is expected in the phase diagram. These phenomena, which are referred to as "liquid-liquid" and "gas-gas" equilibria, give rise to multiple critical points in one-component systems, as well as to critical end points and equilibria of three fluid phases, which can usually be found in multicomponent mixtures only. Furthermore, it is shown that the liquid-liquid demixing in this model is not a consequence of a "softened" repulsive interaction as assumed in the theoretical derivation of the model. Experimental data for the melt density of polybutadiene with molecular mass Mw=45,000 gmol are correlated here using the PC-SAFT equation. It is shown that the discrepancies in modeling the polymer density at ambient temperature and high pressure can be traced back to the liquid-liquid phase separation predicted by the equation of state at low temperatures. This investigation provides a basis for understanding possible inaccuracies or even unexpected phase behavior which can occur in engineering applications of the PC-SAFT model aiming at predicting properties of macromolecular substances. 相似文献
110.
The reaction of N-(3,4-dichlorophenethyl)-N-methylamine (1) with 3-chloromethyl-5-phenyl-1,2,4-oxadiazole (2) was investigated. Employment of an equimolar amount of 1 and 2 in the presence of potassium carbonate led to the expected tertiary amine 3 (N-[(3,4-dichlorophenyl)ethyl]-N-methyl-N-[(5-phenyl-1,2,4-oxadiazol-3-yl)methyl]amine), whereas an excess of 1 and prolonged reaction time resulted in ring fission of the oxadiazole system in 3 and finally in the formation of N′-benzoyl-N-[(3,4-dichlorophenyl)ethyl]-N-methylguanidine (4) and N,N′-bis[(3,4-dichlorophenyl)ethyl]-N,N′-dimethylmethanediamine (5). The structures of products 3–5 were determined by means of 1H and 13C NMR-spectroscopy, mass spectrometry and IR-spectroscopy, for 3 (as picrate) and 4 also X-ray structure analysis was employed. A possible mechanism of the reaction pathway leading to compounds 4 and 5 is proposed. 相似文献