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1988 (1)
1Author    W. Preetz, A. Heinrich, J. ThesingRequires cookie*
 Title    c/oso-Halogenohydrohexaborate, IV Protonierung, Deuterierung und Schwingungsspektren von c/aso-Hexaboraten c/oso-Halogenohydrohexaborate, IV Protonation, Deuteration and Vibrational Spectra of c/oso-Hexaborates  
 Abstract    The weak Brönsted acids B 6 H 7 ~ and XB^H,", X = Cl, Br, I; pk a : 7-4,75, are formed by protonation of B 6 H h 2 ~ and XB 6 H 5 2 respectively. The deuteration rates, evaluated from inte-grated IR band intensities of the BH and BD stretching vibrations, are linearly dependent on the mole fractions of the protonated species, and decrease with increasing degree of halogenation in the series Cl>Br>I. H atoms trans-positioned to halogens are exchanged 100 times more rapidly than the remaining ones. The activation energy for the H/D exchange amounts to 76 ± 1,5 kJ/mol for B 6 H 7 ". The lower symmetry of the protonated borates is evident from additional IR and Raman bands. They are distinguished from the corresponding Brönsted bases by a high frequency shift of the BH stretching vibrations in the order of 100 cm '. Due to the pH dependent equilib-rium B h H (S 2 ~/B (,H 7 " and different solubilities of the tetrabutylammonium salts, the separation of BF,H 6 2 "/B 12 H| 2 2 " mixtures is achievable. In alkaline solutions the very soluble B ft H 6 2 ~ is present, whereas (TBA) 2 B, : HI : precipitates quantitatively. By subsequent cautious acidification of the supernatant, insoluble (TBA)B 6 H 7 is obtained. 
  Reference    Z. Naturforsch. 43b, 1319—1326 (1988); eingegangen am 16. Juni 1988 
  Published    1988 
  Keywords    Halogenohydrohexaborates, Protonation Deuteration, IR Spectra, Raman Spectra 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-1319.pdf 
 Identifier    ZNB-1988-43b-1319 
 Volume    43