Organic anions. Part 3. Charge control versus product stability control in the protonation of 1,3-diarylpropenide ions

Abstract

The kinetically controlled reaction of 1,3-diarylpropenide ions (I) in liquid ammonia with either ammonium chloride or methanol gives a mixture of alkenes [(II) and (III)]. The ratios of the products thus obtained can be correlated with the local charges at the benzylic sites as measured by n.m.r. spectroscopy (correlation coefficient r= 0.961–0.981) or, less well, with the relative stabilities of the two products (r= 0.927–0.931). The slope of the ‘charge control’ graph corresponds to a critical interionic separation of 0.8 Å. The best correlation of all (r= 0.989–0.997) is obtained by using a two-parameter equation (7), but the statistical validity and theoretical justification for this remain somewhat obscure. A more limited study has been made for the reaction of the anions (I) with allyl chloride.