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An illustrative example is the effect of catalysts to speed the decomposition of hydrogen peroxide into water and oxygen: . 2 H 2 O 2 → 2 H 2 O + O 2. This reaction proceeds because the reaction products are more stable than the starting compound, but this decomposition is so slow that hydrogen peroxide solutions are commercially available.
For example: Similar reactions will occur far faster if the reaction is intramolecular. ... Consider the reaction of peptide bond hydrolysis catalyzed by a pure ...
In acid catalysis and base catalysis, a chemical reaction is catalyzed by an acid or a base. By Brønsted–Lowry acid–base theory, the acid is the proton (hydrogen ion, H +) donor and the base is the proton acceptor. Typical reactions catalyzed by proton transfer are esterifications and aldol reactions.
Among the types of reactions that can be catalyzed by Lewis acids, those with carbonyl-containing substrates have received the greatest amount of attention.The first major discovery in this area was in 1960, when Yates and Eaton reported the significant acceleration of the Diels-Alder reaction by AlCl 3 when maleic anhydride is the dienophile.
These catalysts initiate radical chain reactions, autoxidation that produce organic radicals that combine with oxygen to give hydroperoxide intermediates. Generally the selectivity of oxidation is determined by bond energies. For example, benzylic C-H bonds are replaced by oxygen faster than aromatic C-H bonds. [2]
Reaction Coordinate. (A) Uncatalyzed (B) Catalyzed (C) Catalyzed with discrete intermediates (transition states) Most metal surface reactions occur by chain propagation in which catalytic intermediates are cyclically produced and consumed. [8] Two main mechanisms for surface reactions can be described for A + B → C. [2]
For example the reaction of acetophenone with bromine to give phenacyl bromide. Oscillating reactions such as the Belousov–Zhabotinsky reaction are more complicated examples that involve autocatalysis. [2] In such reactions the concentrations of some intermediates oscillate, as does the rate of formation of products.
Often, however, cross-coupling refers to a metal-catalyzed reaction of a nucleophilic partner with an electrophilic partner. Mechanism proposed for Kumada coupling (L = Ligand , Ar = Aryl ). In such cases, the mechanism generally involves reductive elimination of R-R' from L n MR(R') (L = spectator ligand ).