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Appearance energies for [M - H](-) ions from phenol (I), 4-chlorophenol (II), pentachlorophenol (III) and pentachlorothiophenol (IV) were measured. The following thermochemical data were deduced from experiment: DeltaH(acid) values of 343.3, 335.7, 317.1 and 317.1 kcal mol(-1) for RH molecules (I, II, III, and IV, respectively) and electron affinities (EAs) of R(.) free radicals 2.55, 2.90, 3.79, and 3.65 eV, respectively. Our data for phenol (I) and 4-chlorophenol (II) demonstrate a higher stabilization of ArO(-) anions than was previously accepted. Using the enthalpic shift procedure for molecules and a series of isodesmic reactions for free radicals, earlier elaborated by the authors, a new Delta$bf H_bf fbf 0$ values for the following gas-phase species were obtained (kcal mol(-1)): C(6)Cl(5)Br (5.0), C(6)Cl(5)SH (8.5), p-ClC(6)H(4)C(.) (2. 0), C(6)Cl(5)C(.) (-15), C(6)Cl(5)S(.) (44). Copyright 2000 John Wiley & Sons, Ltd.  相似文献   
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Vacuum distillation of diethyl ester of cis-4-hydroxy-trans-5-methoxy-trans-1,2-cyclohexanedicarboxylic acid gave a single compound, 5-ethoxycarbonyl-7-methoxy-2-oxa[2.2.2.]bicyclooctan-3-one. The structure of this -lactone was demonstrated by data of NMR and IR spectroscopy. Calculations using the method of molecular mechanics showed that this structure has the highest steric strains of all possible stereoisomeric -lactones.M. V. Lomonosov Moscow State University, Moscow 119899. M. V. Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow 117571. K. D. Ushinskii Yaroslavl' State Pedagogical University, Yaroslavl' 150000. Translated from Khimiya Geterotsiklicheskaya Soedinenii, No. 1, pp. 41–47, January, 1997.  相似文献   
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Protonation of trans-2-aminocyclohexanols leads to dramatic conformational changes: due to an intramolecular hydrogen bond a conformer with equatorial position of ammonio- and hydroxy-groups becomes predominant. The trans-2-aminocyclohexanol moiety has been used for pH-induced conformational switching of a crown ether and a podand.  相似文献   
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Ionization energies of substituted trimethylamines (CH3)2NCH2X, together with appearance energies of [M ? X]+ ions, have been measured by the photoionization technique. The heats of formation for the following radicals have been derived (in kJ mol?1): C2H3˙ (+ 314), Ph. (+ 347), p-CH3C6H4˙ (+ 326), HC2˙ (+ 494), (CH3)2N?H2 (+ 134), NC˙ (+ 452), CF3. (? 435), (CH3)3Si˙ (+ 54.5). The heats of formation obtained for [(CH3)2NCH2]+ (+ 649) and (CH3)3Si+ (+ 610) lead to ionization energies of 5.35 eV for (CH3)2N?H2 and 5.75 eV for (CH3)3Si˙.  相似文献   
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