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In chemistry a carbenoid is a reactive intermediate that shares reaction characteristics with a carbene. [1] In the Simmons–Smith reaction the carbenoid intermediate is a zinc / iodine complex that takes the form of I-CH 2-Zn-I. This complex reacts with an alkene to form a cyclopropane just as a carbene would do.
[citation needed] [18] The transition metal carbene complexes can be classified according to their reactivity, with the first two classes being the most clearly defined: Fischer carbenes, in which the carbene is bonded to a metal that bears an electron-withdrawing group (usually a carbonyl). In such cases the carbenoid carbon is mildly ...
Because the π donation is weak, the carbene carbon is electrophilic in nature. [1] Because of this bonding property, Fischer carbenes often feature: low oxidation state metal center; middle and late transition metals Fe(0), Mo(0), Cr(0) π-acceptor metal ligands; π-donor substituents on the carbene atom such as alkoxy and alkylated amino groups.
A transition metal carbene complex is an organometallic compound featuring a divalent carbon ligand, itself also called a carbene. [1] Carbene complexes have been synthesized from most transition metals and f-block metals, [2] using many different synthetic routes such as nucleophilic addition and alpha-hydrogen abstraction. [1]
The Simmons–Smith reaction is an organic cheletropic reaction involving an organozinc carbenoid that reacts with an alkene (or alkyne) to form a cyclopropane. [ 1 ] [ 2 ] [ 3 ] It is named after Howard Ensign Simmons, Jr. and Ronald D. Smith .
Metal-catalyzed cyclopropanations are chemical reactions that result in the formation of a cyclopropane ring from a metal carbenoid species and an alkene. [1] In the Simmons–Smith reaction the metal involved is zinc. Metal carbenoid species can be generated through the reaction of a diazo compound with a transition metal).
The most reactive metals, such as sodium, will react with cold water to produce hydrogen and the metal hydroxide: 2 Na (s) + 2 H 2 O (l) →2 NaOH (aq) + H 2 (g) Metals in the middle of the reactivity series, such as iron , will react with acids such as sulfuric acid (but not water at normal temperatures) to give hydrogen and a metal salt ...
[3] the metal that stabilizes the carbene, dissociates at the same time but not to the same degree as carbon–carbon bond formation and hydrogen atom migration. The reaction is distinct from a metal catalyzed C−H activation reaction ( sensu stricto ) in which the metal actually inserts itself between carbon and hydrogen to form a species ...