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371.
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373.
Leslie E Thompson Philip M Rice Eugene Delenia Victor Y Lee Phillip J Brock Teddie P Magbitang Geraud Dubois Willi Volksen Robert D Miller Ho-Cheol Kim 《Microscopy and microanalysis》2006,12(2):156-159
Ultramicrotomy, the technique of cutting nanometers-thin slices of material using a diamond knife, was applied to prepare transmission electron microscope (TEM) specimens of nanoporous poly(methylsilsesquioxane) (PMSSQ) thin films. This technique was compared to focused ion beam (FIB) cross-section preparation to address possible artifacts resulting from deformation of nanoporous microstructure during the sample preparation. It was found that ultramicrotomy is a successful TEM specimen preparation method for nanoporous PMSSQ thin films when combined with low-energy ion milling as a final step. A thick, sacrificial carbon coating was identified as a method of reducing defects from the FIB process which included film shrinkage and pore deformation. 相似文献
374.
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376.
Willi E. Oberhnsli 《Helvetica chimica acta》1982,65(3):924-933
The Spontaneous Resolution of the 3,3-Diethyl-5-methylpiperidine-2,4-dione (Methyprylon) into its Optical Isomers. An X-Ray Structure Analysis of an Isodimoophous System of Mixed Crystals Repeated recrystallizations from acetone of a racemic mixture of the title compound successively result in a spontaneous resolution into optical isomers [1]. In this process batches of mixed crystals of increased optical purity are formed [2]. This phenomena was investigated on a molecular basis using X-ray diffraction methods. The mixed crystals belong to the space group P212121 and their diffraction patterns give no indication of major disorders. There is a linear relationship between the changes in unit cell parameters a and b and the optical rotation of the sample. The structures of the mixed crystals from four fractions belonging to two different crystalline modifications have been determined. The molecular shape is such that most of the atomic positions of the two enantiomers superimpose almost perfectly. Occupation factors determined for the asymmetric C- sites agree well with the optical activity of the crystals fraction. 相似文献
377.
Harald Marxmeier Emanuel Pfeil und Willi Wolf 《Fresenius' Journal of Analytical Chemistry》1965,215(5):387-391
Zusammenfassung Konjugierte Diene und Monoene werden colorimetrisch in Kohlenwasserstoffgemischen durch Kupplung mit diazotiertem p-Phenylendiamin bestimmt. Die Methode ermöglicht auch die Bestimmung beider Kohlenwasserstoffgruppen nebeneinander.
Der ESSO-AG Hamburg danken wir für weitreichende Unterstützung der vorliegenden Arbeit und für die Erlaubnis, die gefundenen Resultate zu veröffentlichen.
Herrn Prof. Dr. C. Mahr zum 65. Geburtstag gewidmet.
Marxmeier, H.: Diplom-Arbeit, Marburg 1960.
Wolf, W.: Staatsexamensarbeit, Marburg 1962. 相似文献
Summary Conjugated dienes and monoenes may be determined in mixtures of hydrocarbons by colorimetry of the dye obtained by coupling with diazotized p-phenylenediamine. Both groups of hydrocarbons can also be determined in presence of each other.
Der ESSO-AG Hamburg danken wir für weitreichende Unterstützung der vorliegenden Arbeit und für die Erlaubnis, die gefundenen Resultate zu veröffentlichen.
Herrn Prof. Dr. C. Mahr zum 65. Geburtstag gewidmet.
Marxmeier, H.: Diplom-Arbeit, Marburg 1960.
Wolf, W.: Staatsexamensarbeit, Marburg 1962. 相似文献
378.
Konrad Oertle Harry Beyeler Rudolf O. Duthaler Willi Lottenbach Martin Riediker Eginhard Steiner 《Helvetica chimica acta》1990,73(2):353-358
A stereocontrolled synthetic route to optically pure (?)-(S)-ipsenol ( 1 ), the pheromone of Pityokteines curvidens and various other bark-beetle species is described. Key step of the synthesis is an enantioselective aldol reaction using a chiral titanium–carbohydrate complex (Scheme 1). The carboxylate function of the optically pure β-hydroxy acid 5 thus obtained in mol quantities is then elaborated to the diene moiety by standard methodology (Scheme 2). 相似文献
379.
Frank H. Herbstein George M. Reisner Willi Schwotzer 《Journal of inclusion phenomena and macrocyclic chemistry》1985,3(2):173-182
The crystal structures of three polyiodode salts are reported (pyridinium pentaiodide, monoclinic,P2
1/m,a=9.221(5),b=12.918(5),c=6.026(4) Å, =103.60(7)o,Z=2,R
F=0.087 for 1187 intensities; -naphthyl-ammonium pentaiodide, triclinic,173-1,a=10.390(5),b=9.502(5),c=4.462(3) Å, =99.19(7), =90.40(7),=108.49(8)o,Z=2,R
F=0.059 for 1319 intensities;N-methyl--picolinium heptaiodide, monoclinic,C2/c,a=19.315(7),b=12.714(5),c=8.442(4) Å, =107.26(7)o,Z=4,R
F=0.065 for 1336 intensities). All three structures can be described as having channel inclusion features; the cations are contained in channels in polyiodide frameworks based on different arrangements of I2 molecules and I
3
–
anions. This structural type is the converse of the more widespread kind where polyiodide anions are contained in an organic matrix (e.g., cyclodextrin polyiodides).
Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82016 (30 pages).Part X of Crystal Structures of Polyiodide Salts and Complexes. For Part IX, see F. H. Herbstein, G. M. Reisner, and W. Schwotzer,Acta Crystallogr. C, accepted for publication, 1984 相似文献
380.
Alfred V. Willi 《Helvetica chimica acta》1971,54(4):1220-1232
The energy barrier in proton transfer reactions is described by a Johnston-type equation (1) (n = order of bond to be broken). The barrier model is discussed in terms of free energies. The Vi values are free energies of ionic cleavage in aqueous solution of the X? H and Y? H bonds; they are computed from eqns. (4c) and (4d). The values of p1 and p2 affect curvature (absence or presence of maximum) and symmetry of the barrier. It is postulated that pi is a typical constant of the reacting bond and can be transferred from one transition state to another. With the aid of eqn. (1) and its first derivative, values of pi and nm (bond order at maximum of barrier) can be based on quantities determined experimentally, Δ≠ and ΔG. For O? H bonds, pi ≈ 1.0. For C? H bonds pi is larger than 1.0 and depends on the structure of the carbanionic moiety (influence of resonance and inductive effects). As there cannot be a maximum if p1 = p2 = 1.0, the suggested model of the barrier leads to a better understanding why proton transfer must be ‘fast’ in some reactions and ‘slow’ in others. The computed values of nm may be utilized to gain some insight into the nature of the transition states; they supply a basis for the discussion of primary hydrogen isotope effects. 相似文献