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1Author    Werner Winter, AntonThomas Butters, Rieker, Yasuo ButsuganRequires cookie*
 Title    Synthesis and Structure of l,2-Bis(2,4,6-tri-fert-butylphenyl)ethane  
 Abstract    The title compound 9, C38H62, was prepared by dehalogenation of 2,4,6-tri-£er£-butyl-benzyl chloride (7a). It crystallizes in the monoclinic space group C2/c with Z = 4. a = 10.923(7), b = 17.910(3), c = 17.395(3) A and ß = 91.87(3)° (the cell constants refer to 173 K). The structure was solved by direct methods and refined by full-matrix least squares to 7? = 0.073 for all 3853 reflexions (|Fo| > 0). On account of steric repulsions, the central ethane bond, which lies on a twofold crystallographic axis, is stretched to 1.567(4) A. Close packing of the molecules in layers parallel the ac-plane leads to boat-deformations of the benzene rings. Room-temperature data sets of weakly diffracting crystals [a = 10.948(0), b= 17.97(1), c= 17.52(2) and ß = 91.9(1)°] do not give rise to an artificial shortening of the central ethane bond of 9. Evidently, poor data quality or lack of resolution have not to be considered as an explanation for the unusual short ethane bond [1.47(3) A] in the first undamped hexaphenylethane [Stein, Winter, and Rieker (1978)]. Historical Background 
  Reference    Z. Naturforsch. 37b, 855—862 (1982); received March 15 1982 
  Published    1982 
  Keywords    X-ray, Steric Hindrance, Hindered Ethanes 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-0855.pdf 
 Identifier    ZNB-1982-37b-0855 
 Volume    37 
2Author    Manfred Weidenbruch, Fateh SabetiRequires cookie*
 Title    Organosilylnitrite, -nitrate und verwandte Verbindungen Silicon Compounds with Strong Intramolecular Steric Interactions, V 1 Organosilicon Nitrites, Nitrates and Belated Compounds  
 Abstract    The reaction of triisopropyl-or tricyclohexylhalosilanes with silver salts gives the corresponding silyl nitrites and silyl nitrates. The insertion reaction of sulfur trioxide or dichlorocarbene into the silicon hydrogen bond of triisopropylsilane and tricyclohexyl-silane yields the sulfates and the dichloromethyl derivatives, respectively. 
  Reference    (Z. Naturforsch. 31b, 1212—1215 [1976]; eingegangen am 18. Juni 1976) 
  Published    1976 
  Keywords    Trialkylsilyl Nitrites, Trialkylsilyl Nitrates, Steric Hindrance, Insertion Reactions 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1212.pdf 
 Identifier    ZNB-1976-31b-1212 
 Volume    31 
3Author    Gerhard Müller, Joachim LachmannRequires cookie*
 Title    Sterisch belastete cyclische Phosphanborane Sterically Crowded Cyclic Phosphine-Boranes  
 Abstract    A The anionic phosphine o-(diphenylphosphinomethyl)phenyl L has been used to prepare the sterically crowded cyclic phosphine-boranes BL3, 'BuBL2, and 'Bu2BL by reaction o f the lith-iated ligand LiL with B(OM e)3, 'BuB(OM e)2, and 'Bu2BOMe, respectively. In the new com ­ pounds 'BuBL-, and 'Bu^BL one ligand L is bonded to the boron center by both its carbanionic and its phosptiino function with formation o f five-membered rings. In solution 11B and 31P N M R spectroscopy does not indicate substantial B -P dissociation, i.e., the existence o f three-coordinate boron. The steric bulk o f L in BL3 leads to the formation o f oligom ers in solution, presumably by a bridging coordination mode o f L to two boron centers. N o conclusive evi­ dence as to the monom eric or oligomeric nature o f BL3 in the solid state can be given, however. Five-membered ring form ation is proven for the solid state by X-ray structure determinations o f 'BuBL2 and 'Bu2BL which in addition confirm that the steric bulk o f L is superior to that o f a tert. butyl group. 
  Reference    Z. Naturforsch. 48b, 1248 (1993); eingegangen am 13. Mai 1993 
  Published    1993 
  Keywords    nionic Benzylphosphines, Cyclic Phosphine-Boranes, Crystal Structure, Steric Hindrance 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-1248.pdf 
 Identifier    ZNB-1993-48b-1248 
 Volume    48 
4Author    TeresaB. Orow Iaka, IrenaW. Olska3, A.Rtur Korzańskia, W. Olfgang, M. Iliusb, W. Olfgang Schnickb, W. Iesław, A. Ntkow IakcRequires cookie*
 Title    A Comparison of the Enamino Carbonyl Conjugation Efficiency for Hy­ drogen Bonding Formation in Pyridone and Dihydropyridone Systems  
 Abstract    The crystal structures of two compounds containing enaminone heterodiene systems and forming intermolecular hydrogen bonds N-H--O are reported: 1) 3-ethoxycarbonyl-2-methyl-4-pyridone (hereafter ETPY) and 2) 3-ethoxycarbonyl-2-phenyl-6-methoxycarbonyl-5,6-di-hydro-4-pyridone (hereafter EPPY). The crystal packing is controlled by intermolecular hydro­ gen bonds N-H-0 = C connecting the heteroconjugated enaminone groups in infinite chains. In ETPY crystals the intermolecular hydrogen bond involves the heterodienic pathway with the highest 7r-delocalization that is effective fo ra very short N -O distance of 2.701(9) A (average from two molecules in the asymmetric unit). Probably due to the steric hindrance, the hydrogen bond in EPPY is formed following the heterodienic pathway that involves the ester C = 0 group, although 7r-delocalization along this pathway is less than that along the pyridone-part pathway resulting in a longer N -O distance of 2.886(3) A. In tro d u c tio n 
  Reference    (Z. Naturforsch. 55b, 5—11 [2000]; received August 8 1999) 
  Published    2000 
  Keywords    Pyridone, Dihydropyridone, Enaminone 7r-Conjugated System, Intermolecular Hydrogen Bond, Steric Hindrance 
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 TEI-XML for    default:Reihe_B/55/ZNB-2000-55b-0005.pdf 
 Identifier    ZNB-2000-55b-0005 
 Volume    55 
5Author    Manfred Weidenbruch, Claude Pierrard, Helge PeselRequires cookie*
 Title    Neue Siloxanverbindungen einiger Übergangsmetalle Silicon Compounds with Strong Intramolecular Steric Interactions, VIII [1] New Siloxane Compounds of Some Transition Metals  
 Abstract    Tri-£er£-butylsiloxane compounds of transition metals are obtained by two different routes, one of these involves condensation of tri-Zer£-butylsilanol with the binary oxides V2O5, CrC>3, M0O3, and Re2Ü7, while the other proceeds via a similar reaction between the chlorides VOCl3, NbCls, TaCls, Cr02Cl2, and the silanol. The new compounds, having good thermal stability and remarkable resistence to hydrolysis, are characterized by IR, 1 H NMR, and mass spectra. 
  Reference    Z. Naturforsch. 33b, 1468—47 (1978); eingegangen am 20. September 1978 
  Published    1978 
  Keywords    Tri-ierf-butylsiloxanes, Transition Metals, Steric Hindrance, Mass Spectra 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1468.pdf 
 Identifier    ZNB-1978-33b-1468 
 Volume    33 
6Author    Manfred Weidenbruch, Helge PeselRequires cookie*
 Title    Tri-Jert-butylsiliciumpseudohalogenide Silicon Compounds with Strong Intramolecular Steric Interactions, VII [1] Tri-ferf-butylsilicon Pseudohalides  
 Abstract    Tri-£eri-butylchlorosilane reacts with potassium pseudohalides in the presence of catalytic amounts of the crown ether 18-crown-6 to give the tri-£er£-butylsilicon pseudo-halides (*-C4H9)3SiX (X = CN, NCO, NCS, N3) in good yields. These new compounds are characterized by IR, *H NMR, and mass spectra. In the absence of the crown ether no reaction occurs. Treating tri-£er£-butylsilane with AgX (X = CN, SCN) gives the silicon pseudohalides in low yields. 
  Reference    Z. Naturforsch. 33b, 1465—1467 (1978); eingegangen am 4. August 1978 
  Published    1978 
  Keywords    Tri4er£-butylsilicon Pseudohalides, Steric Hindrance, Crown Ether Catalysis, IR, Mass Spectra 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-1465.pdf 
 Identifier    ZNB-1978-33b-1465 
 Volume    33 
7Author    Manfred Weide, Helge Pesel, ++, Dang Van, Hieu ++Requires cookie*
 Title    mit starken intramolekularen sterischen Wechselwirkungen, IX [1] terf-Butylsubstituierte Di-und Trisiloxane Silicon Compounds with Strong Intramolecular Steric Interactions, IX [1] tert-Butyl Substituted Di-and Trisiloxane s  
  Reference    (Z. Naturforsch. 35b, 31—34 [1980]; eingegangen am 23. August 1979) 
  Published    1980 
  Keywords    l, l, 3, 3-Tetra-£er£-butyldisiloxane-l, 3-diol, Penta-fer£-butyldisiloxanol, Steric Hindrance, Mass Spectra 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-0031.pdf 
 Identifier    ZNB-1980-35b-0031 
 Volume    35