Textbook Question
Predict the major products of the following reactions.
a. 1-methylcyclohexene+ aqueous Hg(OAc)2
b. the product from part (a), treated with NaBH4
10. Addition Reactions
Oxymercuration
1:27 minutesProblem 73
Textbook Question
A common situation occurs when both carbons of the mercurinium ion are secondary. In a situation like the one shown, to which carbon would you expect water to add? That is, would you expect to produce A or B? Explain your answer.
Verified step by step guidance1
Understand the structure of the mercurinium ion: The mercurinium ion is formed during the oxymercuration-demercuration reaction, where a mercury ion bridges two carbons, creating a three-membered ring. This intermediate is crucial in determining the site of nucleophilic attack.
Identify the nature of the carbons involved: In this problem, both carbons of the mercurinium ion are secondary. Secondary carbons are bonded to two other carbon atoms, which can influence the stability and reactivity of the intermediate.
Consider the steric and electronic effects: Water, as a nucleophile, will attack the more substituted carbon due to steric hindrance and electronic effects. The more substituted carbon is typically more stable and can better accommodate the positive charge developed during the transition state.
Analyze the regioselectivity of the reaction: The addition of water to the mercurinium ion is regioselective, meaning it prefers one carbon over the other. In this case, the nucleophile (water) will likely add to the carbon that can best stabilize the transition state, often the more substituted carbon.
Predict the product formation: Based on the analysis, water will add to the carbon that is more substituted, leading to the formation of the alcohol at that position. This results in the production of one specific product, either A or B, depending on which carbon is more substituted.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mercurinium Ion Formation
The mercurinium ion is an intermediate formed during oxymercuration reactions, where mercury adds to an alkene, creating a cyclic structure. This ion stabilizes the positive charge by delocalizing it over the two carbons involved, influencing subsequent nucleophilic attack by water.
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Markovnikov's Rule
Markovnikov's Rule predicts the regioselectivity of electrophilic addition reactions, stating that the nucleophile will add to the more substituted carbon. In the context of mercurinium ions, this rule helps determine which carbon water will preferentially attack, leading to the formation of the more stable alcohol product.
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Steric and Electronic Effects
Steric and electronic effects play a crucial role in determining the site of nucleophilic attack. Steric hindrance can prevent water from attacking the more crowded carbon, while electronic effects, such as hyperconjugation, can stabilize the positive charge on the more substituted carbon, guiding the addition of water.
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