Question

22 multiple choice 2 points which of the following is the best reaction sequence to use if one wants to accomplish a markovnikov addition of water to an alkene with minimal skeletal rearrangement? hydroboration - oxidation oxymercuration - demercuration water + concentrated acid water + dilute acid

Explanation:

Step1: Analyze hydroboration - oxidation

Hydroboration - oxidation gives anti - Markovnikov addition of water to an alkene. So, this option is incorrect.

Step2: Analyze oxymercuration - demercuration

Oxymercuration - demercuration gives Markovnikov addition of water to an alkene. The reaction proceeds through a mercurinium ion intermediate, which is less prone to skeletal rearrangements compared to carbocation intermediates in other reactions (like acid - catalyzed additions).

Step3: Analyze water + concentrated acid

In the reaction of water with concentrated acid (e.g., \(H_2SO_4\)), the reaction proceeds through a carbocation intermediate. Carbocations are prone to 1, 2 - hydride or methyl shifts (skeletal rearrangements) to form more stable carbocations.

Step4: Analyze water + dilute acid

Similar to the reaction with concentrated acid, the reaction of water with dilute acid also proceeds through a carbocation intermediate. Carbocation rearrangements can occur, so this option is not the best for minimal skeletal rearrangement.

Answer:

B. oxymercuration - demercuration