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Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran1

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journal contribution
posted on 08.03.1996 by Roustam Gareyev, Andrew Streitwieser
The equilibrium lithium acidities in THF have been determined for 4-ethynylbiphenyl, EB (pK 21.5−22.3), 3,3,3-triphenylpropyne, TPP (pK 22.3−22.7), and 1-ethynyladamantane, EA (pK 23.7). Ion pairs of (4-ethynylbiphenylyl)lithium are aggregated in the concentration range from 10-4 to 10-3 M, with an average aggregation number of 2.5. (3,3,3-Triphenylpropynyl)lithium ion pairs are partially aggregated at concentrations from 10-5 to 10-3 M; the average aggregation number is 1.2. Cesium acidities in THF have been determined for 3,3,3-triphenylpropyne (pK 29.1−29.9) and 1-ethynyladamantane (pK 31.56). The average aggregation number of (3,3,3-triphenylpropynyl)cesium ion pairs is 6.2 at concentrations of 10-4−10-3 M.