Carbonyl Chemistry and Reactivity (5D) Practice Test

An organic synthesis step in a radiotracer preparation uses nucleophilic addition of hydride to a carbonyl. A solution of cyclohexanone is treated with NaBH$_4$ in methanol at 0°C, then quenched with water. The chemist expects reduction of the carbonyl without changing the carbon skeleton. Which molecule is most likely formed from the reaction described?

In a stability study of a carbonyl-containing prodrug, hydrolysis is proposed to occur through formation of a tetrahedral intermediate. The prodrug is an ester (R–C(=O)–OR') and is incubated at pH 1.0 (0.10 M HCl) and separately at pH 13.0 (0.10 M NaOH) at 25°C. Degradation is faster at pH 13. The central concept is carbonyl reactivity and acyl substitution. Which step is most likely rate-limiting under the basic condition for ester hydrolysis?