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1978 (361)
1Author    M. VeithRequires cookie*
 Title    Cyclische Diazastannylene, II 1 Intermolekulare Lewis-Säure-Base-Addukte bei 1.3.2.4A 2 -Diazasilastannetidinen Cyclic Diazastannylenes, II 1 Intermolecular Lewis-Acid-Base Adducts of 1, 3,2,4A 2 -Diazasilastannetidines  
 Abstract    -diazasilastannetidines can be prepared as mono-mers (organyl = <erf-butyl) or dimers (organyl = isopropyl) in nonpolar solvents, depending on the organic nitrogen substituent. The formation of the dimer, which is due to an intermolecular Lewis-acid-base interaction of Sn(II) with nitrogen, can be initiated by solidification. When the tertf-butyl compound is cooled below 0 °C two crystalline modi-fications are found: a monoclinic phase (C 2/c; a= 10.655(5); b = 24.75(1); c = 17.334(9) Ä; ß = 106.9(1)°) and a triclinic phase (P I; a = 10.68(1); b = 13.51(1); c = 12.36(1) A; a = 96.2(1); ß = 102.6(1); y = 118.4(1)°). The crystal structures turn out to be built of dimeric and monomeric units in the first case and presumably only dimeric species in the second case. The isopropyl derivative crystallizes in the space group P 2i/b (a = 10.77(1); b= 12.14(2); c = 11.15(2) A; ß = 120.2(2)°) with only dimeric units being present, as in the liquid. Interrelationships between the three structures are discussed. 
  Reference    (Z. Naturforsch. 33b, 1—6 [1978]; eingegangen am 5. September/6. Oktober 1977) 
  Published    1978 
  Keywords    Diazastannylenes, Solid State, X-ray, Crystal Structure, NMR l, 3-Diorganyl-2, 2-dimethyl-I, 3, 2, 4A 2 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0001.pdf 
 Identifier    ZNB-1978-33b-0001 
 Volume    33 
2Author    Cyclic Diazastannylenes, Iii, M. VeithRequires cookie*
 Title    Cyclische Diazastannylene, DI 1 Die Kristall-und Molekülstruktur der monoklinen Phase von 1.3-Di-feri-butyl-2.2-dimethyl-1.3.2.4A 2 -diazasilastannetidin The Crystal and Molecular Structure of the Monoclinic Phase of l,3-Di-feri-butyl-2,2-dimethyl-l,3,2,4A 2 -diazasilastannetidine  
 Abstract    The crystal and molecular structure of the monoclinic phase of l,3-di-£eri-butyl-2,2-dimethyl-l,3,2,4A 2 -diazasilastannetidine has been determined from three-dimensional X-ray data collected on a two-circle diffractometer at —120 °C (MoKa radiation, 2623 re-flexions, R — 0,050). The crystals are monoclinic, space group C 2/c, with cell dimensions a = 10.655(5), b = 25.75(1), c = 17.33(1) A, ß = 106.8(1)° and Z = 12. Four monomeric (crystal site symmetry 2 (C2)) and four dimeric units (crystal site symmetry I (Cj)) are present in the structure interacting over tin-tin (3.68 A). Remarkable are the very short Sn-N bond (2.09 A) in the monomer and the donation bond Sn-N (2.39 Ä) in the dimer. The coordination of the tin atoms in the different units is discussed in detail. 
  Reference    (Z. Naturforsch. 33b, 7—13 [1978]; eingegangen am 5. September/6. Oktober 1977) 
  Published    1978 
  Keywords    Diazastannylenes, X-ray, Molecular Structure, Crystal Structure 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0007.pdf 
 Identifier    ZNB-1978-33b-0007 
 Volume    33 
3Author    Cyclic Diazastannylenes, Iv, M. Veith, 0. Reckten, Wald, E. HumpferRequires cookie*
 Title    Cyclische Diazastannylene, IV 1 Zur Oxidation von 1.3-Di-ferf-butyl-2.2-dimethyl-1.3.2.4A 2 -diazasilastannetidin Oxidation of l,3-Di-£erJ-butyl-2,2-dimethyl-1,3,2,4A 2 -diazasilastannetidine  
 Abstract    The reactions of l,3-di-<er^-butyl-2,2-dimethyl-l,3,2,4A 2 -diazasilastannetidine (1) with O2 and Sß or SnCU proceed in two steps: In a first redoxtype reaction an intermediate containing tetravalent tin is formed. Some of these intermediates are unstable with respect to the starting material stannylene 1 and undergo a substitution reaction to yield a spiro-tetraazastannane. Under appropriate conditions the intermediate from the sulfur-and SnCLi-reaction can be isolated and turns out to be either dispiro[3,3,3]distanna-disulfa-disila-tetrazane or a diaza-dichlorostannane respectively. Crystal and kinetic data of some products/reactions are reported. 
  Reference    (Z. Naturforsch. 33b, 14—19 [1978]; eingegangen am 14. September 1977) 
  Published    1978 
  Keywords    Diazastannylenes, Unsymmetrically Substituted Stannanes, Kinetic Data, NMR, Crystal Data 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0014.pdf 
 Identifier    ZNB-1978-33b-0014 
 Volume    33 
4Author    Gert Heller, Bernd BichowskiRequires cookie*
 Title    Darstellung von Polyboraten mit sperrigen tertiären Aminen und quaternären Ammoniumbasen in organischen Lösungsmitteln Preparation of Polyborates with Hindered Tertiary Amines and Quaternary Ammonium Bases in Organic Solvents  
 Abstract    Polyborates, Ammonium Borates, Isopolyanions, Tris(methoxy)borane, Hydrolysis The preparation of polyborates with bulky cations in organic solvents by the method of "ester hydrolysis" as well as by the method of evaporation of solutions of the base and boric acid reactands under reduced pressure with the very strong bases benzyltrimethyl-ammonium hydroxide and benzyltriethylammonium hydroxide leads to [C6H5CH2N(CH3)3][B506(0H)4] and [C6H5CH2N(C2H5)3][B506(0H)4]. The more bulky, but less basic tri-n-butylamine yields a heptaborate, presumably [(C4H9)3NH][B706(OH)XO]. The less bulky, but more basic triethylamine or tri-n-propylamine yield [(C2H5)3NH][B506(0H)4] or [(C3H7)3NH][B506(0H)4]. The most bulky, but less basic benzylamine or tri-n-octylamine are not capable to function as cations in polyborates. 
  Reference    (Z. Naturforsch. 33b, 20—23 [1978]; eingegangen am 3. Oktober 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0020.pdf 
 Identifier    ZNB-1978-33b-0020 
 Volume    33 
5Author    Franz Gerstner, Johann WeidleinRequires cookie*
 Title    N.N' -Dimethylacetamidinderivate des Aluminiums, Galliums und Indiums N,N'-Dimethylacetamidin Derivatives of Aluminium, Gallium and Indium  
 Abstract    The interaction of N,N'-dimethylacetamidine with trialkyl derivatives of alumin-ium, gallium and indium yields dialkylmetal compounds of the structural formula R2M(N2Me2CMe) (M = Al, Ga and In). According to the vibrational data the M2N4C2 skeletons of these dimeric products form a centrosymmetric puckered eight-membered ring, probably with C2h symmetry. The IR-and Raman spectra of the amidine HN(Me)C(= NMe)Me are discussed. 
  Reference    (Z. Naturforsch. 33b, 24—29 [1978]; eingegangen am 3. Oktober 1977) 
  Published    1978 
  Keywords    Dialkylmetal Acetamidin Derivatives, Preparation, Vibrational Spectra 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0024.pdf 
 Identifier    ZNB-1978-33b-0024 
 Volume    33 
6Author    I. M. Issa, E. M. Diefallah, M. R. Mahmoud, A. M. El-, Nady ChemRequires cookie*
 Title    Kinetics of the Alkaline Solvolysis of Trichloroacetate Ion in Water-Ethanol Solutions  
 Abstract    Alkaline Solvolysis, Trichloroacetate Ion The alkaline solvolysis of trichloroacetic acid in water-ethanol mixtures have been studied in the presence of 0.40-0.80 M sodium hydroxide within the temperature range 35-70 °C. The rate constant increased with progressive addition of the organic solvent. The dielectric constant effect on the reaction rate was investigated. The radius of the activated complex at different temperatures was calculated. The isocomposition and isodielectric energies as well a« the thermodynamic parameters of activation were calculated and their significance in terms of solvent composition has been discussed. It was concluded that the reactant state is extensively higher solvated than the transition state by the highly polar (water) solvent. 
  Reference    (Z. Naturforsch. 33b, 30—34 [1978]; received July 15 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0030.pdf 
 Identifier    ZNB-1978-33b-0030 
 Volume    33 
7Author    Christoph Tiburtius, Hans-Uwe SchusterRequires cookie*
 Title    LiBeSb und LiZnBi, ternäre Verbindungen mit Wurtzitgerüst LiBeSb and LiZnBi, Ternary Compounds with a Wurtzit-type Lattice  
 Abstract    Ternary Lithium Compounds, Crystal Data LiBeSb and LiZnBi have been prepared and analytically and structurally characterized. We found a Wurtzit-type lattice with an ordered arrangement of the positions of Be and Sb respectively Zn and Bi. 
  Reference    (Z. Naturforsch. 33b, 35—38 [1978]; eingegangen am 15. September 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0035.pdf 
 Identifier    ZNB-1978-33b-0035 
 Volume    33 
8Author    Horst Rumpel, Wolfgang Berndt, Klemens Adam, Einhard SchwarzmannRequires cookie*
 Title    Neue Oxid-und Hydroxid-Phasen des fünfwertigen Antimons New Antimony(V) Oxides and Hydroxides  
  Reference    (Z. Naturforsch. 33b, 39—42 [1978]; eingegangen am 13. Oktober 1977) 
  Published    1978 
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 Identifier    ZNB-1978-33b-0039 
 Volume    33 
9Author    Aftabuddin Ahmed, Wolfgang Schwarz, Heinz HessRequires cookie*
 Title    Dibrom Preparation and Crystal Structure  
 Abstract    (dimethylamino)alan und Diiod(dimethylamino)alan. Darstellung und Kristallstruktur Dibromo(dimethylamino)alane and Diiodo(dimethylamino)alane. Dibromo(dimethylamino)alane, Diiodo(dimethylamino)alane, Crystal Structure The title compounds were prepared by reaction of dimethylaminoalane with mercury -(II) dibromide and diiodide, respectively, and investigated by X-ray diffraction. Both compounds build structures isotype with that of dichloro(dimethylamino)alane. The molecules exist as dimers with a planar four-membered ring of alternating aluminium and nitrogen atoms. These atoms are four-coordinated. The following bond lengths are found: Al-N 1.94 and 1.95 A, Al-Br 2.26 A, Al-I 2.49 A, N-C 1.50 and 1.55 A. 
  Reference    (Z. Naturforsch. 33b, 43—46 [1978]; eingegangen am 21. Oktober 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0043.pdf 
 Identifier    ZNB-1978-33b-0043 
 Volume    33 
10Author    Ingo-Peter Lorenz, JohnKoshy ThekumparampilRequires cookie*
 Title    Koordinationschemie ambivalenter Liganden, VIII 1 Synthese und Reaktivität ionischer und kovalenter Sulfinato-Komplexe von Tetraorganyl-VB-Elementen des Typs R4'E02SR Synthesis and Reactivity of Ionic and Covalent Sulfinato Complexes of Tetraorganyl-VB-Elements of the Type R4'E02SR  
 Abstract    The synthesis of the sulfinato derivatives 1-7 of pentavalent YB-elements follows equation (2). These compounds differ significantly in their physical and chemical properties and in their structures. In between the extremes of the purely ionic tetramethylam-monium sulfinates la-c and the typically covalent and pentacoordinated tetraorganyl-sulfinato-O-stiboranes 6-7, there are the hexa-or pentavalent compounds of phosphorus and arsenic 2 and 4 or 3 and 5 with sulfinato-0,0' or sulftnato-0 linkage, which dissociate readily into their ionic components. 1 a-c are suitable for the synthesis of sulfones according to equation (3). All of the methylsulfinato derivatives can be easily transformed (equation (4)) into the corresponding sulfonates by air oxidation. Only the tetraphenylsulfinato-O-stiboranes 7 a-c show S02-elimination forming pentaorganylstiboranes (equation (5)). IR, mass and in some cases NMR spectra are reported. 
  Reference    (Z. Naturforsch. 33b, 47—58 [1978]; eingegangen am 22. August/22. November 1977) 
  Published    1978 
  Keywords    Ionic Ammoniumsulfinates, Sulfinato-0 Derivatives, Covalent Tetraorganyl-sulfinato-O-stiboranes, IR, NMR 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0047.pdf 
 Identifier    ZNB-1978-33b-0047 
 Volume    33 
11Author    LauriH J Lajunen, Raekko KivekäsRequires cookie*
 Title    Formation of Copper(II) Complexes of l,3-Diamino-2-propanol in Aqueous Solution  
 Abstract    Copper(II) Complexes, l,3-Diamino-2-propanol The complex formation between Cu 2+ ions and l,3-diamino-2-propanol has been studied potentiometrically at 25 °C, constant ionic strength equal to 0.1 M NaC104, and pH 5-11. The nature of the complexes has been established by examining the standard deviations and values of the agreement index R of different models. 
  Reference    (Z. Naturforsch. 33b, 59—61 [1978]; received October 171977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0059.pdf 
 Identifier    ZNB-1978-33b-0059 
 Volume    33 
12Author    Giacomo Martini, M.Francesca OttavianiRequires cookie*
 Title    ESR Study of Copper Complexes Adsorbed on Fully Hydrated X and Y Zeolites  
 Abstract    ESR, Cu(II) Complexes, Synthetic Zeolites The ESR spectroscopy is used for the study of the motion of Cu(en)2 2+ and Cu(tmen)(OH)2 in fully hydrated X and Y zeolites. At room temperature steric hindrance in the faujasite cavities and slow motion condition lead to partially anisotropic spectra. In frozen samples, calculation of bonding coefficients indicate small interaction with surface walls. 
  Reference    (Z. Naturforsch. 33b, 62—66 [1978]; received October 12 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0062.pdf 
 Identifier    ZNB-1978-33b-0062 
 Volume    33 
13Author    M.Sakhawat HussainRequires cookie*
 Title    Cyclic Amidines Complexes: Complexes of 5:6:ll:12-Tetrahydro-2,8-dimethylphenhomazine with Copper(II), Nickel(II) and Zinc(H)  
 Abstract    Cyclic Amidines Complexes, Copper(II), Nickel(II), Zinc(II) The title compound, PHZ, can be viewed as 1,5-diazacyclooctane (daco) having carbon-3 and carbon-7 fused to benzene rings restricting the vibrational freedom of these carbons and rendering the axial positions in the complexes open for fifth and sixth coordination. Copper(II), nickel(H) and zinc(H) complexes of PHZ have been prepared. Copper(II) formed mono-and bis-complexes, whereas nickel(H) and zinc(II) formed only bis-complexes. The diamagnetic nickel(II) complexes are planar like the corresponding complexes of mesocyclic diamines, daco and dach. The copper(II) complexes differ appreciably from the mesocyclic diamine complexes of copper(II). Zinc (II) formed tetra-hedral complexes with two monodentate PHZ ligands and anions in the first coordination sphere. The structures of the complexes have been assigned by analysis of their spectral, magnetic and conductance data. The thermogravimetric studies of the complexes are also reported and discussed. 
  Reference    (Z. Naturforsch. 33b, 67—74 [1978]; received August 23 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0067.pdf 
 Identifier    ZNB-1978-33b-0067 
 Volume    33 
14Author    NazmiA. Kassab, Sanaa0. Abd, Allah, SaidA. Elb, AhA. TiRequires cookie*
 Title    Arylazoisoxazolinthiones: Preparation and Reactions of 4-Arylazo-3-methyl-2-isoxazolin-5-thiones  
 Abstract    The arylazo derivatives (2) of 3-methyl-2-isoxazolin-5-thione were prepared. Alkylation 
  Reference    (Z. Naturforsch. 33b, 75—79 [1978]; received August 24 1977) 
  Published    1978 
  Keywords    ) Alkylation, Grignard's Reaction, Arylazoisoxazolinimines, Arylazoisoxazolinhydrazones, Ring Cleavage 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0075.pdf 
 Identifier    ZNB-1978-33b-0075 
 Volume    33 
15Author    IanF. Eckhard, NeilG. Keats, LindsayA. SummersRequires cookie*
 Title    Derivatives of 5H-Cyclopenta[2,l-b : 3,4-b']dipyridin-5-one (4,5-Diazafhioren-9-one)  
 Abstract    5H-Cyclopenta[2,I-b: 3,4-b'Jdipyridin-5-one, Diquaternary Salts, Mass Spectra 
  Reference    (Z. Naturforsch. 33b, 80—83 [1978]; received August 8 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0080.pdf 
 Identifier    ZNB-1978-33b-0080 
 Volume    33 
16Author    Wolf-Hellmut GündelRequires cookie*
 Title    Untersuchungen an quartären Pyridinium-Salzen, VII 1 Pyridinium-Salze mit Harnstoff-und Carbamidester-Gruppe. Darstellung einiger Betaine Investigations of Quaternary Pyridinium Salts, VII 1 Quaternary Pyridinium Salts with Urea or Carbamate Group. Preparation of Inner Salts  
 Abstract    Pyridinium Salts, Pyridylurea, Pyridylcarbamate Ten new quaternary pyridinium salts with urea or carbamate group were prepared and the acidity constants determined. On addition of base to the salts ot pyridyl-urea, stable inner salts could be isolated. Bei der Umsetzung von quartären Nikotinsäure-amid-Salzen (1) mit der äquimolaren Menge anioni-scher Base entstehen, wie beschrieben 2 ' 3 , Cyclo-tetrakondensate (3) in zum Teil über 90-proz. Ausbeute. -HX 0 ix© NH 
  Reference    (Z. Naturforsch. 33b, 84—88 [1978]; eingegangen am 27. September 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0084.pdf 
 Identifier    ZNB-1978-33b-0084 
 Volume    33 
17Author    Bildung Von Pyrimidinthionen, Wolfgang Stadlbauer, Thomas Kappe, Erich ZieglerRequires cookie*
 Title    Zur Chemie des Kohlensubsulfids, III 1 Formation of Pyrimidinthiones  
 Abstract    Carbon Subsulphide, 2-Aminopyridine, N-Phenylbenzamidine, ß-Aminocrotonate Carbon subsulphide, C3S2, reacts with 2-aminopyridine (la) and N-phenylbenzamidine (lb) to yield the corresponding higher condensed derivatives 4 and 7. Attempts to obtain mesoionic compounds by reaction of N-substituted 2-aminopyridines or N,N'-disubsti-tuted benzamidines were not successful. Efforts to yield a pyridinethione derivative by reaction of C3S2 with /?-aminocrotonate (lc) failed. In this case the sulphur-bridged compound 8 could be isolated. 
  Reference    (Z. Naturforsch. 33b, 89—93 [1978]; eingegangen am 27. September 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0089.pdf 
 Identifier    ZNB-1978-33b-0089 
 Volume    33 
18Author    Klaus Albert, Jürgen HambrechtRequires cookie*
 Title    Intramolekulare Austauschprozesse in Cyclopentadienyl-Systemen. Strukturabhängigkeit der Energiebarrieren Intramolecular Exchange Processes in Cyclopentadien Systems. Structural Dependence of Activation Barrieres  
 Abstract    2-Hydroxy-2-(2',6'-dimethoxyphenyl)-l,3-diphenyl-cyclopenta-[l]-phenanthren, 
  Reference    (Z. Naturforsch. 33b, 94—99 [1978]; eingegangen am 26. September 1977) 
  Published    1978 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0094.pdf 
 Identifier    ZNB-1978-33b-0094 
 Volume    33 
19Author    Klaus Albert, Hans-Peter Schneider, Dieter Koch, Anton RiekerRequires cookie*
 Title    Synthese und 13 C-NMR-Spektren ferJ-butylierter Cyclohexenon-Epoxide Synthesis and 13 C NMR Spectra of £erf-Butylated Cyclohexenone Epoxides  
 Abstract    Phenol Degradation Products, Epoxidation, Cyclohexenone Epoxides, 13 C PFT NMR 13 C NMR spectra of several cyclohexenone epoxides obtained by oxygenation of 4-R-2,6-di-<er<-butylphenols have been assigned, using substituent induced shifts, off-resonance and C-H single-frequency-decoupling techniques, as well as completely C-H coupled spectra. For the -butyl signals the following sequence rules are relevant: 
  Reference    (Z. Naturforsch. 33b, 100—105 [1978]; eingegangen am 10. Oktober 1977) 
  Published    1978 
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 Identifier    ZNB-1978-33b-0100 
 Volume    33 
20Author    Claudia Bäk, Klaus PraefckeRequires cookie*
 Title    Photoreaktionen 2.2'-dihalogensubstituierter Benzoinether und Benzildimethylmonoketale in Lösung 1 Photoreactions of 2,2'-Dihalogen Substituted Benzoin Ether and Benzildimethylmonoketals in Solution  
 Abstract    The synthesis of a,a'-dihalogenated benzoin ether 6 and benzildimethylmonoketals 7 are discribed. Their reaction behavior under UV irradiation and electron impact conditions are discussed in comparison with those of arylesters 1 of seleno and thiobenzoic acid. The photoproducts of 6 and 7 are separated and identified with help of column or vaporphase chromatography. Photoinduced a-cleavages of 6 and 7 produce 2-halogenbenzoyl radicals 9 and a-monomethoxybenzyl radicals 10 or a,a-dimethoxybenzyl radicals 15 resp., which undergo four different stabilization reactions under formation of 1) 2-halogenbenzaldehydes 12 from 9 by hydrogenabstraction, 2) 2,2'-dihalogenbenzils 11 and l,2-di(2-chlorophenyl)-1,2-dimethoxyethan (13) via dimerization of 9 or 10 resp., 3) methylesters 16 of 2-halogen-benzoic acids by /^-elimination of methylradicals from 15, and 4) 2-halogenacetophenones 17 via combination of 9 with methylradicals from 15. In addition to these photoproducts 2-phenylbenzoic acidester 18, benzaldehyde (19), and acetophenone (20) are formed by photosubstitution of halogens in benzaldehydes 12 as well as in acetophenones 17 against hydrogen and in benzoic acid-esters 16 against phenyl resp. Independent photoexperi-ments prove 1) the formation of 2-phenylbenzoic acidester 18 by halogen-phenylreplace-ment in 16 and 2) that chlorine is easier than bromine, both in orZ/io-position to a carboxyl function, substituted by phenyl. No photoproducts {e.g. 8 or 14) are formed by substitution of halogen in the 2-halogenbenzoyl part of a-cleavage against neither a-monomethoxybenzyl nor a,a-dimethoxybenzylradicals resp. as expected like the photoinduced formation of selenoxanthones or thioxanthones 2 from selenol-or thiolesters 1. 
  Reference    (Z. Naturforsch. 33b, 106—112 [1978]; eingegangen am 5. Oktober 1977) 
  Published    1978 
  Keywords    Carbonyl Compounds, a-Cleavages, Free Radicals, Aromatic Photosubstitutions 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0106.pdf 
 Identifier    ZNB-1978-33b-0106 
 Volume    33 
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