Substitution Reactions of Alkyldiazonium Ions

An analysis of the stereochemistry of deamination has also been done using 4-r-butylcyclohexylamines and the conformationally rigid 2-decalylamines. The results are summarized in Table 4.2. 

In solvent systems containing low concentrations of water in acetic acid, dioxane, or sulfolane, the alcohol is formed by capture of water with net retention of configuration. This result has been explained as involving a solvent-separated ion pair that 

Heggvik, K. Sorbye, and A. Fiksdahl, Tetrahedron Asymmetry, 8, 2193 

CH3CO2HH H—O2CCH3 CH3CO2H -O2CCH3 CH3CO2H HO2CCH3 

It is clear from the data in Table 4.2 that the two pairs of stereoisomeric cyclic amines do not form the same intermediate. The collapse of the ions to product is evidently so fast that there is not time for relaxation of the initially formed intermediates to reach a common structure. Generally speaking, we can expect similar behavior for all alkyl diazonium ion decompositions. The low activation energy for dissociation and the neutral and hard character of the leaving group result in a carbocation that is free of direct interaction with the leaving group. Product composition and stereochemistry is determined by the details of the collapse of the solvent shell. 

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