Question

Epoxides, like bromonium ions and mercuronium ions, can be ring-opened with various nucleophiles. The stereochemistry of the product depends on if the ring-opening occurs under acidic or basic conditions. The following two reactions – ring opening of an epoxide with water – illustrate this effect. Explain why the outcome of the reaction changes under these two conditions and provide electron-pushing arrows to explain the mechanisms.

PHOLD H30*/H20 PHOI OH | PhD NaOH,H,O HO D

Answer 1

1200 no Pho ne In the presence of Acidic medium the oxygen of epoxide gets protonated and then Nucleophilic ring openning by H2O occur from more hindered site of epoxidi due to more stablized partial charge at more hindered carbon. Mechanisma ol en of her mot fram til on BMG nn phi - Ph ooo 10. Ano o دا- Backside attack of t20 Juno L-120 мой MO,,,, ,ng Reason behind this effecta Product SO 141 less stablized so more Stabized so by th effect of Phenyl So favoury Nucleophilic attack at this center more.

When Baseis used or only Nucleophile used Substituted carbon. prefer less Noonllo Home Mechanisma Ph...OPD Ph. Hlion b on 0 HY an ph.. .on > - Ngon Product So mechanism clearly explains how both products are formed