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The association constants for charge‐transfer (CT) complex formation of a series of methylated benzene donors with 1,2,4,5‐tetracyanobenzene and tetracyanoethylene as acceptors were measured. In several cases the values determined previously using standard analysis techniques, such as Benesi–Hildebrand or related methods, were shown to be incorrect and a new method for determining the association constants for weak complexes is presented. A systematic error occured in the determination of these constants when standard analysis was carried out on weakly bound complexes. In general, the thermodynamic stabilities have been underestimated and the extinction coefficients for the CT absorptions overestimated. Furthermore, it was demonstrated that the ground‐state stabilization of the complexes studied here is due primarily to non‐bonded interactions and that the ion‐pair contributions are minor in the ground state. A notable exception may be the tetracyanobenzene–hexamethylbenzene complex where preliminary evidence points to a significant contribution of the ion‐pair state to the ground‐state stability. This study raises significant questions about what is currently known concerning the thermodynamics of CT complexes because much of what is believed may be based on incorrectly determined constants. Copyright © 2000 John Wiley & Sons, Ltd.

Successful conjugate additions to 2-bromocyclohexenone and 2-bromocyclopentenone have been achieved with a variety of lithium homocuprates, mixed cyanocuprates, and lithium tri-sec-butylborohydride as well. In all cases the resulting -bromo enolate anions could be trapped on oxygen with acetic anhydride; 3-substituted 2-bromo enol acetates were thus obtained regiospecifically and in good yields (Table II, 65-95%). Attempts to extend

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