M. Pregel, E. Buncel
1993
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0
Influential Citations
133
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Journal
Journal of the American Chemical Society
Abstract
In the reaction of p-nitrophenyl methanesulfonate (1) with alkali-metal ethoxides, it is found that potassium ethoxide in the presence of excess 2.2.2 cryptand is more reactive than potassium ethoxide alone or in the presence of excess 18-crown-6. An upward curvature in the plot of k[sub obs] vs [KOEt][sub o] in the presence of 2.2.2 cryptand is interpreted as arising from parallel reactions of free ethoxide ion and the ion pair of ethoxide ion with cryptated potassium ion ([K [contained in] 2.2.2][sup +]EtO[sup [minus]]), the latter being more reactive than the former. It is shown that the ester reacts predominantly by an E1cb-type elimination mechanism, and the potassium cryptate appears to stabilize the transition state for leaving-group departure by electrostatic interactions through an 18-membered ring window' in the cryptand. 13 refs., 3 figs., 6 tabs.