Reaction mechanisms carbon atoms

Electronically excited states of organic molecules, acid-base properties of, 12,131 Energetic tritium and carbon atoms, reactions of, with organic compounds, 2, 201 Enolisation of simple carbonyl compounds and related reactions, 18,1 Entropies of activation and mechanisms of reactions in solution, 1,1 Enzymatic catalysis, physical organic model systems and the problem of, 11, 1 Enzyme action, catalysis of micelles, membranes and other aqueous aggregates as models of, 17. 435... 

For a discussion of the formation of biomolecules in carbon atom reactions see P. B. Shevlin, D. W. McPherson, and P. MeUus, Tbe Reaction of Atomic Carbon with Ammonia. The Mechanism of Formation of Amino Acid Precursors, J. Am. Chem. Soc. 1983, 105, 488 and G. Flanagan, S. N. Ahmed and P. B. Shevlin, The Formation of Carbohydrates in the Reaction of Atomic Carbon with Water, J. Am. Chem. Soc. 1992, 114, 3892. 

The reaction proceeds via a free radical mechanism with homolytic fission occuring between the carbon-carbon atoms. The mechanism of reactions for the cracking of propane is ... 

There is an alternative mechanism for this reaction that involves nucleophilic attack on the alkene instead of on the saturated carbon atom. This mechanism leads to the same product and is often called the SN2 (pronounced S-N-two-prime ) mechanism. 

The Benzilic Acid Rearrangement When benzil is treated with sodium hydroxide, benzilic acid is fornied and the reaction appears to proceed by the intramolecular addition of a group with an electron pair to the carbonyl carbon atom. A mechanism which seems quite plausible for the reaction is the following.50 It is identical mechanistically with the glyoxal-glyoolic acid rearrangement (p. 107). 

An attempt to prepare reduced S-quinolinones from cyclohexane-1,3-diones (or their tautomers) and 3-amino-2-metbyiacrolein gave 1,8-acridinediones with the loss of one carbon atom (a mechanism for this reaction has been suggested). The acridinediones were also synthesized (in 40-79% yield) from the cyclohexane-diones, propanal and ammonium acetate. Further investigation of the former synthesis showed that quinolinones are also produced in the reaction but as they are oils, they had to be isolated as their salts (see also Chapter 53). 

Another example involves the soxurce of acetylene as a major product from the reaction of recoiling carbon atoms and cyclopropane (18). MacKay and Wolfgang attributed the formation of acetylene from carbon-atom reactions with alkanes to an insertion into a C—bond followed by fragmentation of the intermediate carbene (18). The hi yield of labeled acetylene from cyclopropane was in accord with this mechanism, since the intermediate cyclopropylmethylene was believed to cleave into two stable molecules ethylene in addition to acetylene. 

With primary alkyl halides, the free primary carbocation is too unstable. The actual electrophile is a complex of aluminum chloride with the alkyl halide. In this complex, the carbon-halogen bond is weakened (as indicated by dashed lines) and tho-e is considerable positive charge on the carbon atom. The mechanism for the aluminum chloride-catalyzed reaction of ethyl chloride with benzene is as follows ... 

This reaction does not lead to any formation of the [Cr(H20)5Br] + ion, in line with attack at the a-carbon atom. This mechanism is formally analogous to Sis2 attack by mercury(ii) ion at alkylcobaloximes. ... 

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