1825-62-3Relevant articles and documents
NMR DETERMINATION OF ABSOLUTE SITE-SPECIFIC NATURAL ISOTOPE RATIOS OF HYDROGEN IN ORGANIC MOLECULES. ANALYTICAL AND MECHANISTIC APPLICATIONS
Martin, G. J.,Sun, X. Y.,Guillou, C.,Martin, M. L.
, p. 3285 - 3296 (1985)
It has been shown that the "internal" isotope distribution within a given molecular species at the natural abundance level is accessible by a new method, SNIF-nmr, which is based on deuterium NMR.Relative internal factors, Ri/j, have been defined which enable the isotope content of a given site, i, to be compared to that of another molecular site, j, taken as a reference.Several referencing methods intended to provide direct access to relative externals, Ti, and absolute, (D/H), site-specific parameters, are now discussed from both the theoretical and the experimental points of wiev.In the intramolecular referencing method, which involves a time-consuming chemical transformation of the sample, the risk exists of more or less systematic errors resulting from discriminating fractionation effects.However this technique offers, conversely, an interesting way of investigating kinetic isotope effects without the need for specific labelling.In spite of its lower spectral precision the external referencing method has the advantage of being fast and less sensitive to systemetic errors and may be used for direct rough routine determinations of the site-specific isotope contents.More precise results can be obtained, at the price of contaminating the sample, when an intermolecular reference is added and signal heights are used, remembering however that the intensity parameters then have no strict physical meaning in terms of absolute isotope contents.The site-specific parameters, Ti and (D/H)i thus accessible, provide new information on the mechanisms of the fractionation effects occuring in natural conditions and exaples are considered.
-
Hance,Hauser
, p. 994 (1953)
-
Pitt,C.G.,Fowler,M.S.
, p. 1928 - 1930 (1968)
Unimolecular Decomposition of Ethoxytrimethylsilane
Herold, David A.,Furtell, Jean H.
, p. 984 - 988 (1989)
A study of the metastable spectra from ethoxytrimethylsilane and the mass shifts of the deuterium-labeled species permitted the rationalization of the fragmentation mechanism for forming all major ions in the mass spectrum.A new mechanistic pathway for th
Sustainable Catalytic Synthesis of Diethyl Carbonate
Putro, Wahyu S.,Ikeda, Akira,Shigeyasu, Shinji,Hamura, Satoshi,Matsumoto, Seiji,Lee, Vladimir Ya.,Choi, Jun-Chul,Fukaya, Norihisa
, p. 842 - 846 (2020/12/07)
New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO2 and alcohols. Using tetraethyl orthosilicate (TEOS) and CO2 with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS. Under the same conditions, DEC can be synthesized using a wide range of alkoxysilane substrates by investigating the effects of the number of ethoxy substituent in alkoxysilane substrates, alkyl chain, and unsaturated moiety on the fundamental property of this reaction. Mechanistic insights obtained by kinetic studies, labeling experiments, and spectroscopic investigations reveal that DEC is generated via nucleophilic ethoxylation of a CO2-inserted Zr catalyst and catalyst regeneration by TEOS. The unprecedented transformation offers a new approach toward a cleaner route for DEC synthesis using recyclable alkoxysilane.
Metal-Free Catalytic Reductive Cleavage of Enol Ethers
Chulsky, Karina,Dobrovetsky, Roman
supporting information, p. 6804 - 6807 (2018/11/02)
In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.