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'Lithium Dialkylamide Bases' in keywords Facet   Publication Year 1989  [X]
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1989[X]
1Author    L. Xie, W. H. SaundersRequires cookie*
 Title    Is  
 Abstract    o to p e E ffe c ts in K in e tic E n o la te F o r m a tio n fro m 2 -P e n ta n o n e a n d 2 -P e n t a n o n e -l , l , l -d 3 This paper is dedicated to Professor Jacob Bigeleisen on the occasion of his 70th birthday 2-Pentanone and 2-pentanone-l,l,l-d3 were treated with three-fold excesses of lithium diiso-propylamide (LDA) or lithium hexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) with and without hexamethylphosphoric triamide (HMPA, 3 mol per mol of base) at temperatures ranging from 24 to — 70 °C. The deuterium kinetic isotope effects calculated from the product ratios (mea­ sured by GLC as trimethylsilyl enol ethers) showed a range of temperature dependences: none (LDA in THF), attenuated with A^jA^ = 2.53 (LHMDS in THF), and normal with /1H//1D~0.6 indicating moderate tunneling (LDA and LHMDS in THF-HMPA). The variation in temperature dependence is attributed to reaction via multiple base species in which HMPA affects the equilibria between the base species. 
  Reference    Z. Naturforsch. 44a, 413 (1989); received January 13 1989 
  Published    1989 
  Keywords    Isotope Effects, Kinetic Enolates, Temperature Dependence, Lithium Dialkylamide Bases 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0413.pdf 
 Identifier    ZNA-1989-44a-0413 
 Volume    44