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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 607-613 
    ISSN: 1572-8854
    Schlagwort(e): Thiophene ; conjugated ene-ynes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal structures of two conjugated ene-yne derivatives of thiophene are described, 2,5-di-(trimethylsilylethynyl)-3,4-dibromothiophene (1), is triclinic P $$\bar 1$$ witha=6.3281(4)Å,b=9.7421(6)Å,c=16.3669(9)Å; α=80.516(5)°, β=84.810(5)°, γ=74.072(5)°,Z=2,R=0.054; 2,3,4,5-tetra(trimethylsilylethynyl)thiophene (2), is monoclinic, P21/c with a=20.928(2)Å b=5.852(1)Å,c=23.907(2)Å; β=100.245(6)°,Z=4,R=0.049. The ethynylic C atoms of both compounds lie near the thiophene plane, with deviations in the range 0.010(3)–0.455(4)Å. The phenyl groups of2 form a dihedral angle of 13.0(4)°.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 29 (1999), S. 1057-1059 
    ISSN: 1572-8854
    Schlagwort(e): isoconfertiflorin ; sesquiterpenes ; pseudoguaianolide ; ambrosanolide ; conformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The sesquiterpene lactone isoconfertiflorin, C17H22O5, 1, crystallizes in trigonal space group P31 with a = 10.4498(5), c = 12.7516(8) Å, V = 1205.9(2) Å3, and Z = 3. It differs from confertiflorin in having an endocyclic C=C bond in the lactone ring, which carries an exocyclic methyl group. The seven-membered ring adopts an approximate twist-chair conformation with C10 lying in the local two-fold axis, and asymmetry parameter ΔC2 = 5.8°. The cyclopentanone ring has the half-chair conformation with C4 on the local two-fold axis, and ΔC2 = 0.9°. The lactone ring is almost planar with maximum deviation 0.014(2) Å. Both methyl groups on the 7-membered ring are β–oriented. The acetyl group at C8 has an α orientation.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 24 (1994), S. 811-813 
    ISSN: 1572-8854
    Schlagwort(e): Selenadiazole ; Cyclodecadiene ; conformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract 4,5,6,10,11,12-hexahydrocyclodeca[1,2-d∶6,7-d′]bis[1,2,3]selenadiazole, C10H12N4Se2, crystallizes in triclinic space group P $$\bar 1$$ witha=5.4625(3),b=7.2091(4),c=8.3122(6) Å, α=65.313(5), β=77.476(5), γ=77.442(5)°,V=287.35(4) Å3,Z=1. The structure was refined toR=0.031 andR w=0.030 for 2018 observed reflections. The molecule lies on an inversion center. The cyclodecadiene ring adopts an elongated chair conformation. The near-zero torsion angle of the elongated chair lies at the ring-fusion bonds, with a magnitude of 2.9(3)°. The five atoms of the selenadiazole ring exhibit maximum deviation 0.005(2) Å from planarity, with the adjacent carbon atoms lying respectively 0.020(2) and 0.059(2) Å to the same side of this plane. The torsion angles about the bonds comprising the sides of the elongated chair vary in magnitude from 61.0(2)° to 55.7(2)°. The cyclodecadiene C=C bond lengths are 1.368(2) Å. The selenium-carbon bond length is 1.850(2) Å. The Se−N distance is quite long, 1.888(2) Å.
    Materialart: Digitale Medien
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