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  • 1990-1994  (3)
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  • 1
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 0,0,0-propan-1,2,3-trithiobenzoate (3TBZ) has been determined by direct methods. Crystals are monoclinic,a=6.810(2),b=35.950(2),c=9.415(2) Å,β=94.78(2)°, space group P21/c,Z=4. The structure was refined using full-matrix least-squares toR=0.078,R w=0.064, 1957 reflections CuK α radiation, λ=1.5418 Å. The molecule has one relatively short S---C (methylene) intramolecular distance, S(2)---C(38)=3.440(4)Å, approximately 1.5 Å less than the shortest S---C distance observed in related crystal structures. An hypothesis related to this short contact is proposed in order to account for the unusual pyrolitic behavior of this compound in the solid state.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of three thionobenzoates have been determined: O,O-propan-1,3-dithionobenzoate (2TBZ-A) is tetragonal witha=13.086(2),c=19.048(2) Å, space groupI41/a,Z=8; O,O-2,2-dimethylpropan-1,3-dithionobenzoate (2TBZ-B) is monoclinic witha=13.851(5),b=12.428(3),c=10.996(4) Å,β=104.01(4)°, space groupP21/c,Z=4; and O,O,O,O-pentaerythritol-tetrathionobenzoate (4TBZ) is triclinic witha=15.423(4),b=10.924(3),c=10.698(2) Å,α=112.43(2),β=100.64(2), γ=104.57(2)°,Z=2, space groupP¯1. The structures were all solved by direct methods and refined by least squares toR=0.046 for 886 reflections (2TBZ-A),R=0.075 for 1458 reflections (2TBZ-B) andR=0.075 for 2975 reflections (4TBZ),I〉3σ(I) in each case, CuKα radiation, λ=1.5418 Å. The minimum S---CH2 intramolecular distances in these three structures are significantly larger than the minimum corresponding distance in O,O,O-propan-1,2,3-trithionobenzoate (3TBZ) (Moore and Palmer, 1990), thus providing a possible explanation of why 2TBZ-A, 2TBZ-B, and 4-TBZ are inert with respect to pyrolitic solid-state isomerization; whereas 3TBZ readily undergoes thermally induced rearrangement (Das, 1978; Hedgley, 1981).
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: disturbance ; fertilizer ; nitrogen ; nutrient enrichment ; phosphorus ; secondary succession ; species richness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of annual additions of mineral N and P (100 kg ha−1) on plant species composition and annual aboveground net primary production (ANPP) were investigated during the first three years following disturbance in a semi-arid ecosystem. Additions of N reduced richness of perennial plant species during years 2 and 3, while P reduced the number of perennial species only in year 3. From year 1 to year 2, annual and biennial species richness declined in all treatments while ANPP of annual species increased greatly. Added N increased ANPP of annual species while it decreased ANPP of most perennial species relative to the unfertilized control treatment. Community similarities were higher for the control and native vegetation than for other pairs of treatments using both species presence and plant production data. Nitrogen additions have retarded but not completely arrested secondary succession in this system.
    Type of Medium: Electronic Resource
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