the best leaving group", and hence, what will be the predominate product of a given reaction In general, for tetrahedral intermediates involving anionic leaving groups you can assume that the best leaving group will be that group which has the strongest conjugate acid R fr anionic leaving groups, m general, the group which has the strongest conjugate acid (forms the most stable anion) wube the best leaving group ifR1-OHis a stronger acid than R,OH, R1-o vill be the preferred leaving group For example, consider the intermediate shown below. The potential leaving groups are methoxide and phenoxide. The conjugate acids of methoxide and phenolate anions are methanol, pk=16, and phenol, pk=9 (approximate pk values The strongest acid is phenol, and the major product formed will be ethy l acetate. -strongest acid e best leaving group H CH3-OH =94 Another example: the tetrahedral intermediate shown below has two potential leaving groups, chloride and phenoxide. The strongest con jugate acid is HCl hence chloride anion is most likely to leave and the ma jor product will be pheny l acetatethe "best leaving group", and hence, what will be the predominate product of a given reaction. In general, for tetrahedral intermediates involving anionic leaving groups, you can assume that the best leaving group will be that group which has the strongest conjugate acid. For example, consider the intermediate shown below. The potential leaving groups are methoxide and phenoxide. The conjugate acids of methoxide and phenolate anions are methanol, pKa=16, and phenol, pKa=9 (approximate pKavalues). The strongest acid is phenol, and the major product formed will be ethyl acetate. Another example; the tetrahedral intermediate shown below has two potential leaving groups, chloride and phenoxide. The strongest conjugate acid is HCl, hence chloride anion is most likely to leave and the major product will be phenyl acetate