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Often cross-coupling reactions require metal catalysts. One important reaction type is this: R−M + R'−X → R−R' + MX (R, R' = organic fragments, usually aryl; M = main group center such as Li or MgX; X = halide) These reactions are used to form carbon–carbon bonds but also carbon-heteroatom bonds.
Notably, no polymer-supported catalysts were used; for these real-world examples of heterogeneous catalytic cross-coupling on scale, inorganic heterogeneous catalysts (such as Pd/C) are far cheaper and more robust than polymer-supported ligated Pd catalysts, and thus more commonly employed. Scheme 1.
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.
Synergistic catalysts have been used for a variety of reactions, especially when both substrates require some kind of significant activation either with stoichiometric amounts of an activator or through a separate reaction beforehand. Synergistic catalysts differ from other multi-catalyst systems by the nature that one catalyst activates one ...
Often, substances are intentionally added to the reaction feed or on the catalyst to influence catalytic activity, selectivity, and/or stability. These compounds are called promoters. For example, alumina (Al 2 O 3) is added during ammonia synthesis to providing greater stability by slowing sintering processes on the Fe-catalyst. [2]
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]
In chemistry, plasmonic catalysis is a type of catalysis that uses plasmons to increase the rate of a chemical reaction. [1] A plasmonic catalyst is made up of a metal nanoparticle surface (usually gold, silver, or a combination of the two) which generates localized surface plasmon resonances (LSPRs) when excited by light. [2]
The graph for these equations is a sigmoid curve (specifically a logistic function), which is typical for autocatalytic reactions: these chemical reactions proceed slowly at the start (the induction period) because there is little catalyst present, the rate of reaction increases progressively as the reaction proceeds as the amount of catalyst ...