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Saitama
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Solving Grignard Reagent Homework Problem
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In summary: Chemweb?Please?In summary, the student is trying to come up with a solution to a homework problem that they are having trouble understanding. They mention that they need to replace one of the Br's with MgBr, but the answer key states that this is incorrect. They also mention that they may need to do something with the alkyne group, but they are not sure what this entails. Finally, they ask for help from another student and receive it. It is suggested that the alkyne group may be an allene, and if this is written as R- then it is near the correct answer. However, the student can't seem to get the final compound correct.
- #2
AGNuke
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Write it as Br--Mg--R-. Does R- rings a bell? What does the answer key suggests anyway?
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Saitama
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AGNuke said:
Thanks AGNuke for the help!
The answer key suggests that its an allene.
If i write it as R-, I do get near to the answer but yet i can't seem to make the final compound. See attachment for my attempt. The negative charge and pi bonds form a conjugated system so there will be resonance.
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- #4
AGNuke
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What about that negative charge attacking CH2 and Br exiting? I am sure you would get CH2=C=C=CH2. As a matter of fact. It is a method to prepare otherwise hard to prepare cumulene.
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Saitama
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AGNuke said:
I still don't get it.
Care to explain a bit more.
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AGNuke
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Lets number the C-atoms in the diagram. The C-atom attached with Br-Mg be 1 and that last atom attached with Br be 4.
There are lone pair on C-3. They can act as a nuclophile and can attack C-4. On C-4, lone pairs from C-3 are coming and Br is going. This is SNi. And we get Butatriene.
There are lone pair on C-3. They can act as a nuclophile and can attack C-4. On C-4, lone pairs from C-3 are coming and Br is going. This is SNi. And we get Butatriene.
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Saitama
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AGNuke said:
How is it SNi? As far as I remember, this mechanism is found only during the reaction of R-OH with SOCl2 and there is one more reaction where this mechanism is found but it is definitely not related to what you have said. I think its related to Neighbouring Group participation but I would like to confirm it.
- #8
AGNuke
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Substitution Nucleophilic Internal. It is also linked to many forms of NGP.
- #9
Saitama
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AGNuke said:
I know what's the meaning of SNi but I can't agree with you until you give me some references.
- #10
AGNuke
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Wikipedia?
FAQ: Solving Grignard Reagent Homework Problem
What is a Grignard reagent?
A Grignard reagent is an organometallic compound formed by reacting an alkyl or aryl halide with magnesium metal in an ether solvent. It is commonly used in organic synthesis as a strong nucleophile and base.
How do you solve a Grignard reagent homework problem?
To solve a Grignard reagent homework problem, first identify the reactants and products involved. Then, use the general reaction mechanism for Grignard reagents to determine the intermediate and final products. Finally, balance the chemical equation and check for any errors or missing information.
What are some common mistakes when working with Grignard reagents?
Some common mistakes when working with Grignard reagents include using the wrong solvent, not properly drying the reagents, and not controlling the reaction temperature. Additionally, care must be taken to avoid any contact with moisture or air, as this can lead to side reactions or decomposition of the reagent.
What are some applications of Grignard reagents?
Grignard reagents are widely used in organic synthesis to form new carbon-carbon bonds. They are particularly useful for creating complex molecules, such as pharmaceuticals, natural products, and polymers. They can also be used in industrial processes, such as the production of alcohols and acids.
How can I predict the outcome of a Grignard reagent reaction?
The outcome of a Grignard reagent reaction can be predicted by considering the electronic and steric effects of the reactants. For example, more electrophilic carbon atoms are more likely to react with the Grignard reagent. Additionally, steric hindrance can affect the regioselectivity of the reaction, leading to different products. Familiarity with common reaction mechanisms and patterns can also aid in predicting the outcome of a Grignard reagent reaction.