Ch_322a_8.010

Ch_322a_8.010 - Divalent Carbon Species Carbenes Neutral...

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Divalent Carbon Species Carbenes Neutral carbon species with only two bonds to carbon are called carbenes . C . . only 6 valence electrons electron-deficient but neutral Carbenes react rapidly with alkenes with a high degree of stereospecificity . Methylene CH 2 This structurally simple carbene is prepared by decomposition of a highly toxic compound, diazomethane : CH 2 N 2 diazomethane (a gas) C N N : H H : C=N=N H H : - + + - C N H H - + =N resonance structures Decomposition of Diazomethane CH 2 -N N : - + heat or h ! :CH 2 + :N N : methylene highly reactive
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Addition Reactions of Methylene The reactions of methylene are usually carried out in diethyl ether at or near room temperature. A solution of the alkene and diazomethane (prepared from a precursor compound) is either heated or irradiated to decompose the diazomethane. The methylene reacts as it is formed. A Synthesis of Cyclopropanes C=C + :CH 2 C C CH 2 a cyclopropane A Stereospecific Syn Addition C=C + :CH 2 CH 3 CH 3 H H C C CH 2 CH 3 CH 3 H H cis -1,2-dimethylcyclopropane cis -2-butene
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_8.010 - Divalent Carbon Species Carbenes Neutral...

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