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Nmr spectroscopy has been used to demonstrate that the reported preparation of supposed 3-bromomethyl-2,3-dihydro-1,4-benzoxazine ( 3 ) is in error, the product of the reaction being in reality a monocyclic compound, 4 . An alternative entry to the 3-substituted series is described in the synthesis of the 3-hydroxymethyl derivative, 10 , the structure of which was established by nmr and mass spectroscopy. The previous assignment of structure to 2-carbethoxy-2,3-dihydro-1,4-benzoxazine, prepared by an ambiguous route, and to compounds derived from this ester, is shown to be correct. 相似文献
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U. Amaldi G. Cocconi A.N. Diddens R.W. Dobinson J. Dorenbosch W. Duinker D. Gustavson J. Meyer K. Potter A.M. Wetherell A. Baroncelli C. Bosio 《Physics letters. [Part B]》1977,66(4):390-394
The real part of the proton proton elastic scattering amplitude has been determined from its interference with the Coulomb amplitude at total centre-of-mass energies up to 62 GeV. The observed steady increase of ? with energy indicates that the total proton proton cross section continues to increase well beyond this energy. 相似文献
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R. C. Potter Christel Schneider M. Ryska D. O. Hummel 《Angewandte Chemie (International ed. in English)》1968,7(11):845-856
Previously it was generally assumed that high energy radiation could only initiate radical polymerization in solutions of monomers. However, examples of radiation-induced polymerization have recently become known that proceed via an ionic mechanism. Thus, solutions of a monomer can be polymerized ionically, preferably in the presence of a solid, at low temperatures. Suprisingly, this may also be accomplished with ultra-pure, mainly anhydrous systems, even at room temperature. The nature of the ions has not yet been fully elucidated. 相似文献
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Photoexposure of a water-stable, Ti-alkoxide, (OC6H6N)2Ti(OC6H2(CH2N(CH3)2)3-2,4,6)2, dissolved in a water/pyridine solution yielded an insoluble, solid phase, present in the form of suspended particles and a deposited material on the vertical side-wall of the solution container. Raman analysis of these photoproducts confirmed the UV-initiation of hydrolysis and condensation reactions in the alkoxide reagent. The excitation wavelength dependence of the photostructural effects observed provides insight into the mechanisms contributing to these photoinduced phenomena. The results are extended to enable the photopatterned deposition of physical relief structures directly from solution in this system. 相似文献