Organic anions. Part 2. Spectroscopic studies of 1,3-diarylpropenide ions
Bushby, Richard J.; Ferber, Gerald J.
Журнал:
Journal of the Chemical Society, Perkin Transactions 2
Дата:
1976
Аннотация:
Electronic absorption, <sup>1</sup>H n.m.r. and <sup>13</sup>C n.m.r. spectra have been determined for eight sodium (and in some cases lithium and potassium) 1,3-diarylpropenides (I) in liquid ammonia. These show that, in this medium, contact ion pairs are not formed and that not only the trans,trans-anions (I) but also small amounts of the cis,trans-anions (II) are present. The rate of interconversion of the trans,trans- and cis,trans-forms is too low to be measured by n.m.r. spectroscopy but from the proton-decoupled <sup>13</sup>C n.m.r. spectra of the unsubstituted diphenylpropenide (IIIa) it is possible to measure the rate of rotation of the phenyl group. The barrier to this rotation, Î G <sup>â ¡</sup> rot= 10.9 kcal mol<sup>â 1</sup>, is essentially independent of the nature of the counter-ion (Li<sup>+</sup>, Na<sup>+</sup>, or K<sup>+</sup>).
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