The shown chiral α-bromopropionic acid reacts with OH⁻ to give α-hydroxy acid P, or with Ag₂O/H₂O/OH⁻ to give Q. Which stereochemical statement is correct?
Direct hydroxide substitution occurs by backside SN2 attack at the α carbon, inverting its configuration to form P. Silver-assisted conditions allow neighbouring carboxylate participation: formation and opening of the transient cyclic intermediate involve two inversions, giving net retention in Q. Therefore D. Retention here arises from the reaction pathway, not from preserving the C–Br bond.
More Stereochemistry: Chirality and symmetry of organic molecules with or without chiral centres and determination of their absolute configurations and optical purity. Relative stereochemistry in compounds having more than one stereogenic centre. Homotopic, enantiotopic and diastereotopic atoms, groups and faces. Conformational analysis of acyclic and cyclic compounds. Geometrical isomerism and optical isomerism. Configurational and conformational effects, atropisomerism, and neighbouring group participation on reactivity and selectivity/specificity. Stereoselective and stereospecific synthesis. Enantiomeric excess. questions
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