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1Author    Wolfgang RungeRequires cookie*
 Title    The Molecular Structure of Allenes and Ketenes, XII [1] Four-Bond Proton-Proton Spin-Spin Couplings in Allenes  
 Abstract    Four-bond proton-proton coupling constants in allenes are reported. The substituent effects on the coupling constants are discussed on the basis of the dual-substituent parameter approach. Furthermore, the coupling constants are related to quantum-chemical indices (electron densities, overlap populations) obtained from semiempirical CNDO/S and ab initio STO-3G calculations. The magnitudes of the coupling constants depend upon the polar natures of the substituents as well as upon their charge-transfer abilities (resonance effects) to a com-parable amount. In general, the coupling constants in 1,3-disubstituted allenes are nonadditive in ligand -specific parameters. 
  Reference    Z. Naturforsch. 33b, 932—936 (1978); eingegangen am 18. Mai 1978 
  Published    1978 
  Keywords    Allenes, Proton-Proton Coupling Constants, Substituent Effects 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0932.pdf 
 Identifier    ZNB-1978-33b-0932 
 Volume    33 
2Author    Wolfgang RungeRequires cookie*
 Title    of Allenes and Ketenes, XIII [1] Correlations of Carbon-Proton Spin-Spin Coupling Constants in Allenes with ab initio ST0-3G Overlap Populations  
 Abstract    It is shown that substituent effects on one-bond and long-range carbon-proton coupling constants in monosubstituted allenes parallel quantitatively ab initio STO-3G carbon 2s-hydrogen 1 s overlap populations, irrespectively of whether the substituents are bonded to the allenic skeleton via first-row (C, O) or second-row (Si, S, CI) atoms. 
  Reference    (Z. Naturforsch. 34b, 118—120 [1979]; received September 26 1978) 
  Published    1979 
  Keywords    Allenes, Carbon-Hydrogen Coupling Constants, Substituent Effects 
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 TEI-XML for    default:Reihe_B/34/ZNB-1979-34b-0118_n.pdf 
 Identifier    ZNB-1979-34b-0118_n 
 Volume    34 
3Author    H. C. Marsmann+, W. Raml++, E. Hengge++Requires cookie*
 Title    29 Si-Kernresonanzuntersuchiingeii an Polysilanen 1. Perchlorpolysilane 29 Si NMR Investigations on Polysilanes 1. Perchloropolysilanes  
 Abstract    Several oligomeric perchloro silanes of the type Cl2n+2Sin (n= 1 to 6) were studied by 29 Si NMR. n-Cli2Si5 was synthesized for the first time. Structures of isomeric silanes could be determined by substituent effects. 
  Reference    (Z. Naturforsch. 35b, 35—37 [1980]; eingegangen am 29. Juni/13. September 1979) 
  Published    1980 
  Keywords    Perchlorinated Polysilanes, Structure, 29 Si NMR Spectra, Substituent Effect 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-0035.pdf 
 Identifier    ZNB-1980-35b-0035 
 Volume    35 
4Author    GhazwanF. FadhilRequires cookie*
 Title    Factor Analysis of Long Range Substituent Effects on C-13 NMR Chemical Shifts and Target Factor Testing of Different Types of Substituent Parameters  
 Abstract    A factor analysis technique has been used to analyse 186 long range C-13 substituent chemical shift (scs) of 90 compounds of the general formula X-G-Y; X represents the set of substituents, G is a hydrocarbon skeleton, in some cases unsaturated (phenylene) and in other cases saturated. Y consists of a variety of groups which contain the probe site. The data were taken from the literature. Although they were measured in different laboratories, the solvent was CDC1 3 in every case. From the value of the factor indicator function (IND) it was concluded that two factors were significant. The validity of several empirical and theoretical sub-stituent parameters has been investigated by Target testing. Models were constructed for the sub-stituent effect. Results from Target factor testing, model designing and linear regression analysis have shown that Reynolds' er£ and <r F are the best substituent parameters in reproducing the C-13 substituent chemical shift. 
  Reference    Z. Naturforsch. 47a, 775—780 (1992); received December 10 1991 
  Published    1992 
  Keywords    C-13 nmr, Substituent effect, Factor analysis, Target factor testing 
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 TEI-XML for    default:Reihe_A/47/ZNA-1992-47a-0775.pdf 
 Identifier    ZNA-1992-47a-0775 
 Volume    47 
5Author    V. Hauptgruppe, Vi, Susanne Elbel, HeindirkTom Dieck, Reinhard DemuthRequires cookie*
 Title    Photoelektronenspektren von Verbindungen der  
 Abstract    Methyl-und Trifluormethyl-Cyanphosphine, MeKP(CN)3_n und (CF3)MP(CN)3.,l (n = 0,1, 2, 3) Photoelectron Spectra of Group V Compounds, VI 1 Methyl-and Trifluoromethyl-Cyanophosphines, MenP(CN)3_" and (CF3))iP(CN)3.)l (» = 0, 1, 2, 3) The He I photoelectron spectra of the series R"P(CN)3_n (R = Me, CF3; n = 0, 1, 2, 3) and of Me2ECN (E = N, P, As) are interpreted. The PE assignments are based on the comparison with the PE data of analogous halogeno and hydrogen derivatives as well as related cyano compounds and on simple MO considerations (composite molecule-ap-proach). Hyperconjugative and inductive effects of the substituents CN, Me, F, Cl, and especially CF3 are assessed. The various effects of changing substituents or central atoms within the series are used to confirm the interpretation. The differing electronic structures of halogeno and cyano (pseudohalogeno) compounds are discussed on the basis of their PE spectra. 
  Reference    (Z. Naturforsch. 31b, 1472—1479 [1976]; eingegangen am 3. August 1976) 
  Published    1976 
  Keywords    PE Assignment, Substituent Effects, MO Models, Electronic Structures, Symmetry Properties 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1472.pdf 
 Identifier    ZNB-1976-31b-1472 
 Volume    31 
6Author    Shinjiro Kobayashi3, W. Olfram SchnabelbRequires cookie*
 Title    Reactions of Substituted Vinyl Cations in Acetonitrile Solution as Studied by Flash Photolysis, Part II  
 Abstract    n 2 + Vinyl cations o f the structure ;C = C —R (I+) were generated by flash photolysis o f the R 1 2 1 corresponding halides. Lifetime measurements with the aid o f optical absorption measure­ ments yielded bimolecular rate constants k2 o f the reaction o f I+ with tetrahydrofuran and sev­ eral aliphatic alcohols. On the basis o f k2 values the steric effect o f various substituents R 1 and R2 at C2 and the combined mesomeric (+ M) and inductive (-1) effect o f substituent groups at C, on the electrophilicity o f I+ have been elucidated. 
  Reference    Z. Naturforsch. 47b, 1319—1323 (1992); received March 9 1992 
  Published    1992 
  Keywords    Vinyl Bromide, Electrophilicity, Flash Photolysis, Substituent Effect, Steric Effect 
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 TEI-XML for    default:Reihe_B/47/ZNB-1992-47b-1319.pdf 
 Identifier    ZNB-1992-47b-1319 
 Volume    47 
7Author    Serge David, Michel Gourdji, Lucien Guibé, Alain PéneauRequires cookie*
 Title    Chlorine Substituted Acetic Acids and Salts. Effect of Salification on Chlorine-35 NQR  
 Abstract    The NQR of a quadrupolar probe nucleus is often used to investigate the effect of substituent in molecules. The inductive effect, based on a partial charge migration along the molecular skeleton is the only one present in saturated aliphatics, the conjugative effect appearing in conjugated molecules, especially aromatics. As the stepwise charge migration mechanism, formerly used to explain the inductive effect, is now believed obsolete, we have wanted to reexamined the case of chlorine substituted acetic acids and salts. The data in literature was extended by observing reso-nances and determining NQR frequencies in several acids and salts. The present analysis of the salification of mono-, di-and tri-chloroacetic acids, which is equivalent to a deprotonation or the substitution of the acid hydrogen by a negative unit charge, shows that a model based on the polarization of the chlorine atom(s) by the carboxyle group is consistent with experimental results: the polarization energy appears to be proportional to the NQR frequency shifts; experimental data show a correlation between the NQR frequency shifts accompanying salification and the variations of the intrinsic acidity measured in the gas phase; this, in turn shows that there is a proportionality between the polarization energy and the variations in the acid free enthalpy of dissociation. From the comparison between fluorine, chlorine, bromine and iodine, it also appears that an alternative mechanism, the polarization of the carboxyl group by the halogen, would be important only in the case of the fluoroacetic acid. 
  Reference    Z. Naturforsch. 51a, 611—619 (1996); received October 10 1995 
  Published    1996 
  Keywords    35 C1 NQR, Chloroacetic acids, Substituent effect, Inductive effect, Polarization, Intrin-sic acidity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0611.pdf 
 Identifier    ZNA-1996-51a-0611 
 Volume    51 
8Author    Hans Bock, Sabine Nick, Wolfgang Seitz, Christian Näther, JanW. BatsRequires cookie*
 Title    Structures of Charge-Perturbed or Sterically Overcrowed Molecules, 80 [1 -3] Structural Changes of /?-Benzoquinone by Donor and Acceptor Substituents  
  Reference    Z. Naturforsch. 51b, 153—171 (1996); eingegangen am 29. Mai 1995 
  Published    1996 
  Keywords    Crystal Structure, Oxo-and Alkylamino-Substituted p-Benzoquinone Derivatives, Substituent Effects, Cyanine Distortion, AM 1 Calculations 
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 TEI-XML for    default:Reihe_B/51/ZNB-1996-51b-0153.pdf 
 Identifier    ZNB-1996-51b-0153 
 Volume    51 
9Author    Norbert Auner, Carola Wagner, Wolfgang ZieheRequires cookie*
 Title    Silaheterocyclen, XXVII. Substituenteneffekte zur Steuerung des Cycloadditionsverhaltens von Silaethenen [1] Silaheterocycles, XXVII. Controlling the Cycloaddition Behavior of Silenes by Substituent Effects [1]  
 Abstract    The silene Cl2Si=C(Ph)CH2Bu' (2) is formed by the reaction o f l,l,l-trichloro-2-phenyl-l-silaprop-2-ene (1) with LiBu' in n-pentane in the temperature range from -1 5 to 0 °C. TTie reaction initially leads to the corresponding a-lithio adduct A (addition o f LiBu' to the vinyl group of 1); subsequent LiCl elimination yields 2 as an intermediate. 2 can be trapped by Me3SiOMe (3) and dienes which add across the Si=C bond. In the absence of trapping agents but in the presence of the Lewis base N E t3 the mixture 1/LiBu' reacts to give the disilacyclobutane 4. Due to its electronic and steric properties, Cl2Si=C(Ph)C H 2Bu' (2) and butadienes yield mainly the D iels-A lder adducts (5, 7, 9) while with styrene and 1,3-cyclo-hexadiene the [2 + 2] and [4 + 2] products are formed in competition. With 2-norbornene, 2,5-norbornadiene and quadricyclan the [2 + 2] and [2 + 2 + 2] products are formed selectively but only in low yields. In all reactions except with quadricyclan an ene-reaction com petes with the cycloaddition leading to ene-com pounds as by-products. 
  Reference    Z. Naturforsch. 49b, 831 (1994); eingegangen am 18. Februar 1994 
  Published    1994 
  Keywords    Silaheterocycles, l, l, l-Trichloro-2-phenyl-l-silaprop-2-ene, Substituent Effects, Formation of Silenes, Cycloaddition Reactions 
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 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-0831.pdf 
 Identifier    ZNB-1994-49b-0831 
 Volume    49