Hello everyone today we will discuss oxymercuration-demarcation of alkene reaction mechanism in an electrophilic addition reaction. As the use of reagents Hg(OAc)2 for the Transformation of alkene to alcohol. For the demarcation use the reagent NaBH4 as a reducing agent.
Hg(OAc)2 Reaction with Double bond
That is the method of alcohol formation from hydrating alkenes. We have to summarise the overall reactions as electrophilic addition reactions. The reagents are Hg2+ salt such as Mercury acetate in the aqueous solvent in the case used as THF.
- Product formations regioselectivity predict by Markovic rules. Where the major product is the formation of more highly substituted alcohol. This reaction must be mentioned that this is not a selectivity.
The reaction proceeds via the formation of cyclic Mercurinium ion. After that, the Mercurinium ion is opened by attacking the hydroxy group from water. With this the reaction is complete. This whole reaction is Oxymercuration. After this complete step 1 in Oxymercuration-Demercuration of Alkenes. Now,
Step-2
What is Demercuration?
We have to remember that the -OH part of water attacks the center with the more substituted carbon. Now added the Sodium Borohydride NaBH4 reducing agent which removes the Mercury legend. This process calls Demercuration.
- The procedure for the next reaction is the same except that alcohol is used instead of water. This method is called Alkoxymercuration.
Problem-solving on Hg(OAc)2 Reagents:
First of all, you can try to solve these problems as the above instructions we hope it is very easy to find out the major product prediction. All those steps or procedures learn by example.
Q.9. Predict the Major product C with the proper mechanism.
Answer:
That is the method of alcohol formation from hydrating alkenes. We have to summarise the overall reactions as electrophilic addition reactions.
The reagents used in Oxymercuration-Demercuration of Alkenes
Step-1: Reagents (Oxymercuration of the double bond)
(i) Hg(OAc)2 with the aqueous solution.
Step-2: Reagents (Demercuration of the double bond)
(ii) Reducing Agents Sodium Borohydride NaBH4. Which is to reduce or remove the -Hg(OAc) group. Mercury is hygienic in case remove the Mercury using the Reducing agents.
The Reaction with the mechanism is shown given below.
Important Notes:
- Hydrogenation of alkene and formation of a secondary alcohol. According to Markovic’s rules, Aqueous Nucliophile is attacked in secondary carbon. And the formation of a good yield of a secondary alcohol.
- After attacking the Hydroxy group add the reducing agent and corresponding to remove the Hg(OAc) group.
Reaction Mechanism of Oxymercuration-Demercuration:
After Oxymercuration added the Sodium Borohydride (NaBH4) reducing agent which removes the Mercury legend. Finally formation of a secondary alcohol. In case Secondary alcohol is a more stable product compared to a primary alcohol.
Proper Reaction mechanism of question 9
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| Reaction mechanism of question-9. |
Now, we have to take similar questions the concept is more clear. For practice or a clear approach of Oxymercuration-Demercuration reaction using Mercury(II) acetate reagents.
Q.10. Predict the Major product B with the proper mechanism.
Answer: Formation of a tertiary alcohol.
The Reaction with the reaction mechanism is shown given below.
Reaction Mechanism of Oxymercuration-Demercuration of Alkenes Questions.10.
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| This is the reaction mechanism of question 10. |
Now, take one more question. Just to clear another topic. Let’s see question 11.
Q.11. Predict the Major product A with the proper mechanism.
Answer:
The Reaction with the reaction mechanism is shown given below.
Reaction mechanism of question-11
We hope the Oxymercuration-Demercuration of Alkenes Reaction using Mercury(II) acetate is understood very easily. If have any doubt you can contact us -our team solves your problem as soon as possible. Otherwise, that is a helpful session we hope.
Refarence:
We have to prepare a few resources for reading and a more advanced level book and research article. Which resource helps students as well as research fellow or junior researchers/ work on the project in chemistry? the answer is yes.
- Brown, H. C.; Kurek, J. T. J. Am. Chem. Soc. 1969, 91, 5647. https://doi.org/10.1021/ja01048a042
- Organic chemistry by Zweifel problem solution– chapter -5
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