Azide ions ring-substituted cumyl derivatives

The azide ion product selectivity (A az/A s)obsd = 0.7 observed for reactions of ring-substituted cumyl derivatives [XC6H4C(Me2)Y) when X is strongly electron-withdrawing is consistent with as 0.7M for formation of an association... 

Figure 2.2. The change with changing aromatic ring substituent X in the azide (az) ion selectivities (feaz/ s)obsd ( ) determined by analysis of the products of the reactions of ring-substituted 1-phenylethyl derivatives (X-l-Y) and ring-substituted cumyl derivatives (X-2-Y) in 50/50 (v/v) water/trifluoroethanol at 25 The selectivities are plotted...

The addition of two o-methyl groups to ring-substituted cumyl derivatives to give derivatives (28) causes only a modest change (< 5-fold) in feobs for reaction in 50 vol.% CF3CH2OH-H2O 2,6-Me2/2,6-H2 rate ratios for X = MeO, Me, and H are 0.63, 1.7, and 4.4, respectively. However, for the sterically hindered cation (29, X = Me) there is a 70-fold decrease in and a 60-fold increase in fee the product rate-constant ratios for partitioning of (29) between substitution and elimination reactions promoted by solvent (feg and fee) and by azide ion and fes, respectively) have also been discussed. 

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