Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran<sup>1</sup>
1996-03-08T00:00:00Z (GMT) by
The equilibrium lithium acidities in THF have been determined for 4-ethynylbiphenyl, EB (p<i>K</i> 21.5−22.3), 3,3,3-triphenylpropyne, TPP (p<i>K </i>22.3−22.7), and 1-ethynyladamantane, EA (p<i>K</i> 23.7). Ion pairs of (4-ethynylbiphenylyl)lithium are aggregated in the concentration range from 10<sup>-4</sup> to 10<sup>-3</sup> M, with an average aggregation number of 2.5. (3,3,3-Triphenylpropynyl)lithium ion pairs are partially aggregated at concentrations from 10<sup>-5</sup> to 10<sup>-3</sup> M; the average aggregation number is 1.2. Cesium acidities in THF have been determined for 3,3,3-triphenylpropyne (p<i>K</i> 29.1−29.9) and 1-ethynyladamantane (p<i>K </i>31.56). The average aggregation number of (3,3,3-triphenylpropynyl)cesium ion pairs is 6.2 at concentrations of 10<sup>-4</sup>−10<sup>-3</sup> M.