Search results for "Mechanism"
showing 10 items of 1835 documents
Density Functional Theory Study of the Cycloaddition Reaction of Furan Derivatives with Masked o-Benzoquinones. Does the Furan Act as a Dienophile in…
2002
The molecular mechanism for the cycloaddition reaction between 2-methylfuran and a masked o-benzoquinone has been characterized using quantum mechanical calculations at the B3LYP/6-31G theory level. An analysis of the results on the reaction pathway shows that the reaction takes place along a polar stepwise mechanism. The first and rate-determining step corresponds to the nucleophilic attack of the furan ring on the doubly conjugated position of the 2,4-dienone system present at the masked o-benzoquinone to give a zwitterionic intermediate. Closure of this intermediate affords the formally [2 + 4] cycloadduct. For the second step two reactive channels have been characterized corresponding t…
Competing Ring-Photoisomerization Pathways in the 1,2,4-Oxadiazole Series. An Unprecedented Ring-Degenerate Photoisomerization
2002
The irradiation of some 5-alkyl-3-amino-1,2,4-oxadiazoles at lambda = 254 nm in methanol in the presence of triethylamine (TEA) gave ring-photoisomerization both into 2-alkyl-5-amino-1,3,4-oxadiazoles and, unprecedently, into the ring-degenerate 3-alkyl-5-amino-1,2,4-oxadiazoles. The competing ring contraction-ring expansion route and the internal cyclization-isomerization mechanism explain the results.
1984
A dimeric biradical •M plays a central role in the initiation of the spontancous polymerization of methyl methacrylate (M1). Besides the initiation step by chain transfer reaction, a change of the multiplicity of ˙M seems to be of importance. Evidence is given by heavy atoms in the solvent or in an inert gas atmosphere, leading to an acceleration of the overall polymerization rate. The observed effect is related to the atomic number of the respective heavy atom. Measurements of the temperature dependence of the effect for carbon tetrachloride show that — as expected — no activation energy is needed for this reaction step. The results are summarized in a reaction scheme for the initiation me…
Palladium-Catalyzed Suzuki Carbonylative Reaction of α-Halomethyl Oxime Ethers: A Regioselective Route to Unsymmetrical 1,3-Oxyiminoketones
2014
Unveiling the Substituent Effects in the Stereochemistry of [3+2] Cycloaddition Reactions of Aryl‐ and Alkyldiazomethylphosphonates with Norbornadien…
2021
Mechanism of stereospecific polymerization of styrene with alkali metal alkyls
2007
Theoretical Study of the 1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides. A DFT Study of Reaction between Trifluoromethyl Thiomethyl Azometh…
1999
The molecular mechanism for the 1,3-dipolar cycloaddition of trifluoromethyl thiomethyl azomethine ylide with acronitrile has been characterized using density functional theory methods with the B3L...