944-02-5Relevant academic research and scientific papers
Polyoxometalate-Gold(I)/H+ Complexes: Air-Stable, Efficient, Polyvalent, and Bifunctional Catalysts
Hueber, Damien,Hoffmann, Marie,De Frémont, Pierre,Pale, Patrick,Blanc, Aurélien
supporting information, p. 5065 - 5072 (2015/11/09)
Gold(I)/H+-polyoxometalate hybrids, with general formula [POM]x-[H]x-1+[R3PAu(MeCN)]+, were synthesized and fully characterized by 31P and 29Si MAS or liquid NMR, FT-I
A change in rate-determining step in the hydrolysis of cyclic ketals
McClelland, Robert A.,Seaman, Esther
, p. 1608 - 1612 (2007/10/02)
A kinetic study is reported of the hydrolysis of 2-methoxy-2-phenyltetrahydrofuran and 2-ethoxy-2-phenyltetrahydrofuran.At pH>6 the rate-determining step involves H+-catalyzed formation of the oxocarbocation, this reaction occuring with cleavage of the exocyclic alkoxy group to produce a cyclic cation.Between pH 5 and pH 6 a change-over occurs and at pH+-catalyzed breakdown of this intermediate is a slower process than the H+-catalyzed oxocarbocation-forming step.Hydroxide ion catalysis makes the hemiketal decomposition faster at higher pH.Analogous cyclic ortho esters (2-alkoxy-1,3-dioxolanes) show this same change in rate-determining step between high pH and low pH, while acyclic acetals, ketals, and ortho esters generally have the oxocarbocation-forming stage rate determining at all acidities.It is concluded that the structural features inherent in the cyclic systems are responsible for the difference.In particular, the oxocarbocation-forming stage involves exocyclic bond cleavage, giving it an entropic advantage over the hemiketal oe hemiorthoester breakdown which is endocyclic.
