Question

This is a practice MCAT problem from The Princeton Review. I would have thought that there was an oxidation/reduction reaction with raclopride-H+ losing a proton. What am I missing here?

Question 24 Passage 5 (Questions 22 - 26) Many drug molecules must cross the cell membrane to reach their site of action One such drug, raclopride, is a potent D2 dopamine receptor antagonist. Scientists have suggested that raclopride enters the cell using a translocation method that involves lipid hydrolysis of the plasma membrane. The proposed mechanism for the hydrolysis reaction is shown below (Figure 1) Which of the following occur(s) in the reaction shown in Figure 1? I. Oxidation II. Elimination III. Saponification 0 O A. Ionly O B. I only Correct Answer membrane lipid C. I and II only Your Answer O D. I and III only Question Explanation B. Item I is false. There is no change in the oxidation states in any of the individual atoms in the reaction shown in Figure 1 (eliminate choices A and C). Item II is true During the reaction, an ester is converted into a carboxylic acid. Carboxylic acid lyso-PC

Thanks!

Answer 1

Esters can be hydrolysed in both acid and basic medium.

H田 0st OS1

Above example is an acid catalysed hydrolysis. The process is catalysed by H⁺ to enhance the electrophilicity of the carbonyl carbon by orotonation of its oxygen. Water acts as nucleophile .Further it eliminates alcohol to form an acid.

Mechanism is given below

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チHt H20 0f

There is no change in oxidation state of any atons or ions.

Therefore it is only an elimination reaction.